4.1

Summary

GRAM-POSITIVE BACTERIA

STAPHYLOCOCCUS

• Staphylococcus species are Gram-positive cocci that appear in pairs and clusters.
• Staphylococcus aureus is coagulase-positive.
• Coagulase-negative Staphylococcus (CONS) species include S. epidermidis, S. saprophyticus, and S. haemolyticus.
• A blood culture with an Antimicrobial Removal Device (ARD) is ordered if a patient is already on antimicrobials.
• For blood cultures, samples are taken from two sites. Growth from only one site often suggests contamination with coagulase-negative skin flora.

1. Staphylococcus aureus

• S. aureus is a component of the normal flora of humans and can be found on fomites and in dust.
• S. aureus is the most common cause of pyogenic skin & soft tissue infection.
• Bacteremia is common with S. aureus infections.
• Tissue invasion and injury from S. aureus are due to its toxins and enzymes.
• The hallmark of an S. aureus infection is the formation of an abscess.
• Transmission of S. aureus is primarily by direct contact and auto-inoculation.
• S. aureus is the most important cause of neonatal infections.
• S. aureus is the most common cause of osteomyelitis and suppurative arthritis in children.
• S. aureus is a common cause of acute endocarditis.
• S. aureus is the most common cause of renal & perinephric abscesses, which are usually hematogenous in origin.
• S. aureus is the principal cause of Toxic Shock Syndrome (TSS).
• Individuals with atopic skin are more susceptible to secondary staphylococcal infections.
• A pimple pop can lead to systemic S. aureus infection, causing osteomyelitis, infective endocarditis, or septic arthritis.
• MRSA stands for Methicillin-Resistant Staphylococcus aureus.

S. aureus - Pathogenesis

• S. aureus produces Enterotoxins A, B, C1, C2, D, and E, which are associated with food poisoning.
• S. aureus produces Exfoliative toxins A and B, which cause Staphylococcal Scalded Skin Syndrome (SSSS).
• S. aureus produces Toxic Shock Syndrome Toxin-1 (TSST-1), responsible for Toxic Shock Syndrome.

S. aureus - Clinical Manifestations

• S. aureus can cause a wide range of infections including pneumonia, sepsis, osteomyelitis, meningitis, acute endocarditis, Toxic Shock Syndrome, and food poisoning.
• In an immunocompromised individual, S. aureus can cause lobar pneumonia.

S. aureus - Diagnosis

• Diagnosis of S. aureus infection is made by isolating the organism from normally nonpermissive sites like cellulitis aspirates, abscess cavities, or blood.
• Laboratory diagnosis involves Gram staining, and testing for Coagulase, clumping factor, or Protein A reactivity.

S. aureus - Treatment

• For initial empiric therapy of a non-life-threatening infection without signs of sepsis, oxacillin is used.
• For initial empiric therapy of a life-threatening infection, vancomycin is used.
• If MRSA is suspected, clindamycin is considered; however, if there is CNS involvement, vancomycin or linezolid is used.
• For less serious infections caused by Methicillin-Susceptible S. aureus (MSSA), oral options include Dicloxacillin, Cefalexin, or Amoxicillin-Clavulanate.
• A common side effect of vancomycin is Red Man Syndrome.
• Dicloxacillin is not recommended for dermatologic use due to poor bioavailability; cefalexin or amoxicillin-clavulanate are preferred alternatives.

Toxic Shock Syndrome (TSS)

• Toxic Shock Syndrome (TSS) is an acute multisystem disease caused by TSST-1 producing strains of S. aureus.
• TSS is commonly associated with menstruating women using tampons but can also be nonmenstrual.
• TSST-1 causes massive fluid loss from the intravascular space, leading to shock.

TSS - Treatment

• For non-life-threatening TSS, beta-lactamase resistant antistaphylococcals like Nafcillin, Oxacillin, or a 1st generation Cephalosporin are used.
• For life-threatening TSS, Vancomycin is the treatment.

2. Coagulase-Negative Staphylococcus (CONS)

• CONS are normal inhabitants of human skin, throat, mouth, vagina, and urethra.
• S. epidermidis is the most common species of CONS.
• CONS are known to produce a slime layer, which helps them adhere to surfaces like catheters.
• CONS are most commonly associated with catheter infections.

CONS - Clinical Manifestations

• CONS infections can manifest as bacteremia, endocarditis, infections of CSF shunts, and urinary tract infections.

CONS - Treatment

• Most CONS are resistant to Methicillin (functionally considered MRSA).
• The drug of choice for CONS infections is Vancomycin.

STREPTOCOCCUS

1. Streptococcus pneumoniae (Pneumococcus)

• S. pneumoniae is a Gram-positive, lancet-shaped, polysaccharide-encapsulated diplococcus.
• S. pneumoniae is a common inhabitant of the human respiratory tract.
• The polysaccharide capsule is an important pathogenicity factor for S. pneumoniae.
• S. pneumoniae is transmitted via respiratory droplets.
• S. pneumoniae is the most frequent cause of bacteremia, bacterial pneumonia, and otitis media.
• S. pneumoniae is the second most common cause of bacterial meningitis.
• S. pneumoniae is the most common cause of pneumonia in children and older adults.

S. pneumoniae - Clinical Manifestations

• Clinical syndromes caused by S. pneumoniae include otitis media, sinusitis, pneumonia, and sepsis, which can lead to meningitis, osteomyelitis, suppurative arthritis, endocarditis, or brain abscess.

S. pneumoniae - Diagnosis

• Diagnosis of S. pneumoniae is confirmed by isolating the organism from blood or other sterile sites, where it appears as lancet-shaped diplococci on Gram staining.

S. pneumoniae - Treatment

• For penicillin-susceptible meningitis, Penicillin, Cefotaxime, or Ceftriaxone is used.
• For penicillin-nonsusceptible meningitis, a combination of Vancomycin and high-dose Cefotaxime or Ceftriaxone is required.
• For invasive pneumococcal infections outside the CNS, high-dose Cefotaxime or Ceftriaxone is used.
• For patients with a penicillin allergy, alternatives include Clindamycin, Erythromycin, or TMP-SMX.

S. pneumoniae - Prognosis

• The mortality rate for pneumococcal meningitis is 10%.
• Neurologic sequelae of pneumococcal meningitis include sensorineural hearing loss (20-30%), intellectual deficits, blindness, and paralysis.

S. pneumoniae - Prevention

• Two main types of pneumococcal vaccines are available: PPSV23 (polysaccharide) and PCV13/PCV20 (conjugate).
• PPSV23 cannot be given to children younger than 2 years old and does not induce immune memory.
• PCV13 can be given to infants and induces immune memory, contributing to herd immunity.
• The recommended childhood vaccination schedule for pneumococcal vaccine is at 6, 10, and 14 weeks, with a booster at 1 year old.
• Prophylaxis for high-risk children (e.g., post-splenectomy) involves daily oral Penicillin V or monthly IM Benzathine Penicillin G.

2. Group A Streptococcus (GAS) / Streptococcus pyogenes

• Group A Streptococcus (S. pyogenes) are Gram-positive cocci that grow in chains.
• The natural reservoir for GAS is humans.
• Virulence of GAS is primarily due to M protein and erythrogenic toxins.

GAS - Clinical Manifestations

• GAS causes respiratory tract infections like acute pharyngitis and pneumonia.
• GAS causes skin infections like impetigo and erysipelas.
• Untreated GAS pharyngitis (tonsillitis) can lead to cardiac complications, hence treatment for 10 days is crucial.
• Scarlet fever is a GAS infection characterized by a "sandpaper" rash, strawberry tongue, and Pastia's lines (lines in skin folds). Its differential diagnosis includes Kawasaki Disease.
• Severe invasive GAS diseases include GAS Toxic Shock Syndrome and GAS necrotizing fasciitis.

GAS - Diagnosis

• Diagnosis of GAS infection is made by culture (e.g., throat swab).
• Streptococcal antibody titers, such as Antistreptolysin O (ASO) titer and Anti-DNase B, can provide evidence of a recent infection.

GAS - Treatment

• The drug of choice for GAS pharyngitis is penicillin for 10 days.
• For patients with poor compliance, a single IM dose of Benzathine penicillin G can be used.
• Alternatives to penicillin include Amoxicillin, Cephalosporins, Clindamycin, and Macrolides.

GAS - Complications

• Complications of GAS infections are categorized as suppurative or non-suppurative.
• The two major non-suppurative complications are Acute Rheumatic Fever (ARF) and Post-streptococcal Acute Glomerulonephritis (AGN).
• Acute Glomerulonephritis may occur 2 weeks to 1 month after the primary GAS infection.

Rheumatic Fever

Rheumatic Fever - Pathogenesis

• One theory of ARF pathogenesis is the immunologic theory, where components of GAS (like M protein) share antigens with human tissues (heart, brain, joints), leading to immunologic cross-reactivity.
• Another theory is the cytotoxic theory, where enzymes from GAS are directly toxic to cardiac cells.

Rheumatic Fever - Jones Criteria

• The diagnosis of Acute Rheumatic Fever is based on the Jones Criteria: 2 major criteria OR 1 major and 2 minor criteria.
• The major criteria for ARF are: Carditis, migratory Polyarthritis, Chorea (Sydenham), Erythema marginatum, and Subcutaneous nodules.
• Carditis is the most serious manifestation of ARF, with valvulitis being a universal finding. It can lead to murmurs, cardiomegaly, and CHF.
• Migratory Polyarthritis affects large joints and often has an inverse relationship with the severity of carditis.
• Chorea is a late manifestation characterized by emotional lability and uncontrollable movements.
• Erythema marginatum is a non-pruritic, serpiginous rash with pale centers on the trunk and extremities.
• Subcutaneous nodules are firm, painless nodules found over bony prominences.
• The minor criteria include fever, arthralgia, elevated acute phase reactants (ESR, CRP), and a prolonged PR interval on ECG.
• A diagnosis of ARF can sometimes be made without meeting the full Jones criteria in cases of pure chorea, indolent carditis, or recurrent ARF.

Rheumatic Fever - Treatment

• Antibiotic therapy, such as penicillin for 10 days or a single dose of Benzathine penicillin IM, is given to eradicate GAS.
• Anti-inflammatory therapy includes aspirin for arthritis and mild carditis, or corticosteroids (Prednisone) for severe carditis with cardiomegaly or CHF.
• Phenobarbital is the drug of choice for managing chorea.

Rheumatic Fever - Prognosis & Prevention

• Long-term sequelae of ARF are usually limited to the heart (rheumatic heart disease).
• Prognosis depends on the severity of the initial cardiac involvement.
• Primary prevention of ARF involves treating GAS pharyngitis promptly with antibiotics.
• Secondary prevention involves continuous antibiotic prophylaxis (e.g., monthly Benzathine penicillin G) to prevent recurrent attacks in patients with a history of ARF.
• The duration of secondary prophylaxis depends on the presence and severity of residual heart disease, ranging from 5 years to lifelong.

3. Group B Streptococcus (GBS) / Streptococcus agalactiae

• Group B Streptococcus (S. agalactiae) are anaerobic Gram-positive cocci in chains or pairs.
• GBS virulence is attributed to its polysaccharide capsule, surface proteins, and enzymes like B-hemolysin and hyaluronidase.
• GBS is a common etiologic agent of neonatal sepsis, along with E. coli and Listeria monocytogenes.
• Early-onset GBS disease occurs within the first 7 days of life, presents as sepsis or pneumonia, and has a higher fatality rate.
• Late-onset GBS disease occurs after 7 days of life, commonly presents as meningitis, and is associated with acquisition from the environment or community.
• Maternal risk factors for early-onset GBS disease include GBS colonization, previous infant with GBS disease, prolonged rupture of membranes (PROM > 18 hours), and intrapartum fever.

GBS - Diagnosis

• Diagnosis is made by isolating and identifying GBS from normally sterile sites like blood, urine, or CSF.
• Lab findings may include neutropenia/neutrophilia, increased bands, leukopenia, and elevated CRP.

GBS - Treatment

• Initial empiric treatment for suspected neonatal sepsis is a combination of Ampicillin and an Aminoglycoside.
• The drug of choice for confirmed GBS infection is Penicillin G.

GBS - Prevention

• Prevention involves chemoprophylaxis. Pregnant women are screened for vaginorectal GBS colonization at 35-37 weeks of gestation.
• Intrapartum antibiotic prophylaxis, with Penicillin as the drug of choice, is given to GBS-positive mothers to prevent transmission to the newborn.

ENTEROCOCCUS

• Enterococcus species are Gram-positive facultative anaerobes found in pairs or short chains.
• Enterococcus is a common cause of hospital-acquired infections and is frequently resistant to multiple antibiotics.
• E. faecalis accounts for about 80% of infections.
• In neonates, Enterococcus can cause early-onset (<7 days) or late-onset (≥7 days) sepsis, with the latter having a higher mortality rate.
• In older children, Enterococcus is a cause of nosocomial urinary tract infections (15%).

Enterococcus - Treatment

• For minor infections in immunocompetent patients, Ampicillin is used.
• For uncomplicated UTIs, Nitrofurantoin is an option.
• For invasive infections like sepsis or endocarditis, a synergistic combination of Penicillin/Ampicillin and an aminoglycoside is used.

CORYNEBACTERIUM DIPHTHERIAE

• Corynebacterium diphtheriae is an aerobic, Gram-positive bacillus that causes diphtheria, an acute toxin-mediated disease.
• On Gram stain, they appear as club-shaped bacilli, sometimes in a palisading arrangement.
• The organism is an exclusive inhabitant of human mucous membranes and skin.
• Only strains lysogenized by a bacteriophage carrying the tox gene are toxigenic and can cause severe disease.

C. diphtheriae - Pathogenesis

• The diphtheria exotoxin inhibits cellular protein synthesis, leading to tissue destruction and the formation of a pseudomembrane.
• The toxin can be absorbed into the bloodstream, causing systemic effects like myocarditis, neuritis, and kidney tubule necrosis.
• Non-toxigenic strains can cause mild pharyngitis but do not form a pseudomembrane.
• Transmission is via airborne respiratory droplets or direct contact with secretions.

C. diphtheriae - Clinical Features

• The incubation period for diphtheria is 2-4 days.
• Pharyngeal and Tonsillar Diphtheria is the most common form, presenting with sore throat and an adherent, grayish-green pseudomembrane that bleeds on forceful removal.
• Significant soft tissue edema can lead to the characteristic "bull-neck" appearance and airway compromise.
• Laryngeal Diphtheria presents with hoarseness and a barking cough, posing a risk of airway obstruction.
• Anterior Nasal Diphtheria is a milder form with a serosanguineous discharge and a white membrane on the nasal septum.
• Cutaneous Diphtheria appears as nonhealing ulcers with a gray-brown membrane.

C. diphtheriae - Complications

• The most frequent and severe complications are myocarditis and neuritis, which are attributable to the toxin.
• Toxic cardiomyopathy can lead to dysrhythmias and heart failure and accounts for 50-60% of deaths.
• Toxic neuropathy can cause paralysis of the soft palate and other cranial or peripheral neuropathies.

C. diphtheriae - Diagnosis & Treatment

• Diagnosis is made by culture of the lesion.
• The mainstay of therapy is equine Diphtheria antitoxin, which neutralizes unbound circulating toxin.
• Antibiotics (e.g., Erythromycin or Penicillin) are given to halt toxin production and prevent transmission.

C. diphtheriae - Prevention

• Patients require droplet precautions (for pharyngeal disease) or contact precautions (for cutaneous disease).
• Close contacts should receive antimicrobial prophylaxis (Erythromycin or Benzathine penicillin G).
• Vaccination with the Diphtheria toxoid is the most effective means of prevention.

LISTERIA MONOCYTOGENES

• Listeria monocytogenes is a facultative anaerobic, motile, Gram-positive bacillus capable of surviving as an intracellular pathogen.
• Listeriosis is a food-borne illness, often linked to aged soft cheeses, unpasteurized milk products, and contaminated ready-to-eat meats.
• The disease is most common at the extremes of age (newborns and elderly) and in the immunosuppressed.
• In pregnancy, listeriosis can cause a flu-like illness in the mother, potentially leading to seeding of the uterine contents and neonatal infection.

L. monocytogenes - Manifestations

• Early-onset neonatal listeriosis (<5 days) is a multisystem disease acquired in utero, often associated with premature delivery, and has a high mortality rate (>30%). A characteristic finding is granulomatosis infantisepticum.
• Late-onset neonatal listeriosis (≥5 days) is usually acquired after birth, presents as meningitis, and typically affects term infants.
• In older children and adults, it usually affects the immunosuppressed, causing meningitis or sepsis.

L. monocytogenes - Diagnosis & Treatment

• Diagnosis is confirmed by culture from blood or CSF.
• Treatment for listeriosis is Ampicillin, often with the addition of an Aminoglycoside for synergy.
• Alternatives include Vancomycin or TMP-SMX.

GRAM-NEGATIVE BACTERIA

NEISSERIA MENINGITIDIS (Meningococcus)

• Neisseria meningitidis is a fastidious, encapsulated, aerobic Gram-negative diplococcus.
• It is a major cause of meningitis and sepsis (meningococcemia).
• Most invasive disease is caused by serogroups A, B, C, Y, and W-135.
• Transmission occurs through aerosol droplets and contact with respiratory secretions.
• Pathogenesis begins with nasopharyngeal colonization, followed by invasion into the bloodstream.

N. meningitidis - Clinical Manifestations

• Meningococcemia is the dissemination of N. meningitidis into the bloodstream.
• The clinical case definition includes sudden onset of high fever plus signs like neck stiffness, altered consciousness, or a non-blanching rash (petechiae, purpura).
• The hallmark of acute meningococcemia is fever with a non-blanching rash.
• Purpura fulminans is a severe form with widespread purpura, septic shock, hypotension, and DIC.
• The most common clinical manifestation is meningitis with meningococcemia (40% of cases).
• Waterhouse-Friderichsen Syndrome is a devastating complication characterized by diffuse adrenal hemorrhage associated with meningococcemia.
• Poor prognostic signs include the presence of petechiae for <12 hours before admission, absence of meningitis, and a low or normal ESR.
• The most frequent neurologic sequela of meningococcal meningitis is deafness (5-10% of cases).

N. meningitidis - Diagnosis

• The gold standard for diagnosis is the isolation of the organism from blood, CSF, or petechial lesions.
• A rapid presumptive diagnosis can be made from a Gram stain of a needle aspirate from a skin lesion, which shows Gram-negative diplococci.
• Rapid latex agglutination tests on CSF can detect capsular antigens but may have false negatives.

N. meningitidis - Treatment

• Empiric treatment for suspected meningococcal disease is a third-generation cephalosporin (e.g., Ceftriaxone or Cefotaxime).
• Patients should be placed on droplet precautions for 24 hours after the initiation of effective antibiotic therapy.

N. meningitidis - Prevention and Chemoprophylaxis

• Antibiotic prophylaxis is indicated for close contacts who were exposed to the patient's secretions within 7 days before illness onset.
• Prophylactic drugs include Rifampin, Ceftriaxone, or Ciprofloxacin.
• Vaccination is available against serogroups A, C, Y, and W-135 (MenACWY conjugate vaccine) and separately for serogroup B.

HAEMOPHILUS INFLUENZAE TYPE B (Hib)

• Haemophilus influenzae is a Gram-negative coccobacillus.
• Strains are categorized as encapsulated (typeable) or unencapsulated (nontypeable). Type b (Hib) was a major cause of invasive disease before vaccination.
• Humans are the only natural hosts, and transmission is via respiratory droplets.
• Nontypeable strains typically cause noninvasive infections like otitis media and sinusitis.
• Invasive Hib disease historically had a high incidence in young children due to an immature immune response to its polysaccharide capsule.

Hib - Clinical Manifestations

• The most common types of invasive Hib disease are meningitis, epiglottitis, pneumonia, arthritis, and cellulitis.
• Epiglottitis (supraglottitis) is a medical emergency due to the risk of sudden airway obstruction.
• Hib cellulitis classically affects the cheek or periorbital (pre-septal) area, often with a characteristic bluish-purple discoloration.
• Hib septic arthritis commonly affects large joints like the knee, hip, or ankle.

Hib - Diagnosis & Treatment

• Diagnosis is made by Gram staining and culture of specimens from sterile sites.
• The drug of choice for susceptible strains is Ampicillin.
• For invasive disease or resistant cases, a third-generation cephalosporin (Ceftriaxone, Cefotaxime) is used.
• For non-invasive disease like otitis media, Amoxicillin or Amoxicillin-clavulanate is used.

Hib - Prevention

• Invasive Hib disease is now rare in immunized populations due to the highly effective Hib conjugate vaccine.
• Post-exposure prophylaxis with Rifampicin is recommended for household contacts if there is an unimmunized or immunocompromised child in the home.

BORDETELLA PERTUSSIS

• Bordetella pertussis is a small, aerobic Gram-negative coccobacillus that causes pertussis (whooping cough).
• It is extremely contagious and transmitted by aerosol droplets.
• The Pertussis toxin (PT) is the major virulence protein and is responsible for many systemic effects, including profound lymphocytosis.

B. pertussis - Clinical Manifestations

• The illness progresses through three stages:
  1. Catarrhal stage (1-2 weeks): Resembles a common cold with cough, coryza, and low-grade fever.
  2. Paroxysmal stage (2-6 weeks): Characterized by intense, repetitive bursts of coughing (paroxysms) followed by a high-pitched inspiratory "whoop". Post-tussive vomiting is common.
  3. Convalescent stage (weeks to months): Gradual recovery with a lingering cough.
• In infants <3 months old, the "whoop" is often absent, and the presentation may be apnea, gasping, or cyanosis.
• Pertussis should be suspected in any person with a cough lasting ≥14 days, especially with associated paroxysms, whoop, or post-tussive vomiting.
• A key laboratory finding is marked leukocytosis with an absolute lymphocytosis.

B. pertussis - Diagnosis & Treatment

• The gold standard for diagnosis is culture from a nasopharyngeal swab. PCR is also widely used.
• Antibiotics are given to limit the spread of infection and may ameliorate the illness if given early (in the catarrhal stage).
• The drug of choice is a macrolide, such as Azithromycin. Erythromycin is avoided in infants <1 month old due to the risk of pyloric stenosis.
• Infants <3 months old should be hospitalized for monitoring.

B. pertussis - Complications & Prevention

• The most common complications are apnea, secondary pneumonia, and physical sequelae from forceful coughing (e.g., petechiae, epistaxis, hernias).
• Neither natural disease nor vaccination provides lifelong immunity. Protection begins to wane 3-5 years after vaccination.
• Prevention is through vaccination with the acellular pertussis component in DTaP, Tdap vaccines.

SALMONELLA

1. Nontyphoidal Salmonellosis

• Caused by serotypes like S. enteritidis and S. typhimurium.
• It is a major cause of childhood diarrheal illness, primarily transmitted from animal reservoirs (poultry, eggs, reptiles) via contaminated food.
• The most common manifestation is acute enteritis (gastroenteritis) with nausea, vomiting, abdominal cramps, and diarrhea, which is usually self-limited.
• Antibiotics are generally not recommended for uncomplicated cases in healthy children, as they can prolong shedding.
• Antibiotics are indicated for infants <3 months old and high-risk groups (e.g., immunocompromised, sickle cell disease).
• A major complication in patients with sickle cell disease is osteomyelitis.

2. Enteric Fever (Typhoid Fever)

• Caused by Salmonella enterica serovar Typhi (and less commonly, Paratyphi).
• Transmission is exclusively from human carriers via the fecal-oral route (contaminated food or water).
• The incubation period is longer (7-14 days).
• It is a systemic illness where bacteria invade Peyer's patches, enter the bloodstream, and disseminate to the reticuloendothelial system.
• Clinical features include a prolonged, step-ladder fever, malaise, headache, constipation (early) or diarrhea (later), and sometimes "rose spots" on the trunk.
• The gold standard for diagnosis is culture, with bone marrow culture being the most sensitive. Blood culture is most likely positive in the first week.
• Widal test is often used but lacks sensitivity and specificity.
• Treatment requires antibiotics, such as Ceftriaxone, Azithromycin, or a fluoroquinolone (e.g., Ciprofloxacin).
• Dexamethasone is given to severely ill patients with shock or an altered mental state.
• Prevention is through sanitation, safe water, and vaccination (oral live attenuated Ty21a or injectable Vi capsular polysaccharide vaccine).

SHIGELLA

• Shigella species cause bacillary dysentery, a severe inflammatory colitis.
• The infective dose is very low (as few as 10 organisms). Transmission is fecal-oral.
• The target organ is the colon, where the bacteria invade epithelial cells, causing inflammation and ulceration.
• Clinical presentation includes high fever, abdominal cramps, tenesmus (painful defecation), and diarrhea that progresses from watery to grossly bloody and mucoid.
• A classic physical exam finding is a spurt of bloody stool upon digital rectal examination.
• Neurologic findings, especially seizures, are common in young children.
• A severe complication is Hemolytic Uremic Syndrome (HUS), particularly with S. dysenteriae type 1, which produces Shiga toxin.
• The Ekiri syndrome is a rare, rapidly fatal toxic encephalopathy associated with shigellosis.
• Diagnosis can be presumed by finding numerous fecal leukocytes (>50 PMNs/HPF) on a stool smear. Confirmatory diagnosis is by stool culture.
• Treatment includes supportive care (fluids, electrolytes) and antibiotics like Ceftriaxone, Azithromycin, or Ciprofloxacin to shorten the illness and reduce transmission.

Diarrheagenic ESCHERICHIA COLI

• E. coli is a Gram-negative bacillus and a normal inhabitant of the gut. Certain strains cause diarrhea through different mechanisms.
• Enterotoxigenic E. coli (ETEC): Produces heat-labile (LT) and/or heat-stable (ST) toxins. Causes secretory, watery diarrhea. A major cause of traveler's diarrhea and infantile diarrhea in developing countries.
• Enteroinvasive E. coli (EIEC): Invades the colonic mucosa, similar to Shigella. Causes an inflammatory colitis with fever and bloody stools (dysentery).
• Enteropathogenic E. coli (EPEC): A major cause of infant diarrhea in developing countries. Adheres to the small intestine, causing "attaching and effacing" lesions. Leads to non-bloody, mucoid diarrhea that can be persistent.
• Shiga toxin-producing E. coli (STEC/EHEC): Produces Shiga toxins (Stx1, Stx2). Causes hemorrhagic colitis (bloody diarrhea), but fever is uncommon. A major cause of Hemolytic Uremic Syndrome (HUS). The most famous serotype is O157:H7.
• Enteroaggregative E. coli (EAEC): Adheres to the intestinal mucosa in a "stacked brick" pattern. Causes persistent, secretory diarrhea, especially in children in developing countries and AIDS patients.
• Treatment is primarily supportive with fluid and electrolyte therapy. Antibiotics are generally not recommended, especially for STEC (may increase HUS risk).

VIBRIO CHOLERAE

• Vibrio cholerae is a Gram-negative, comma-shaped bacillus that causes cholera.
• Transmission is via contaminated water or undercooked shellfish.
• The organism colonizes the small intestine and produces cholera toxin.
• Cholera toxin leads to massive, cAMP-mediated secretion of chloride and water into the intestinal lumen.
• This results in profuse, watery diarrhea described as "rice-water stools" with a fishy odor.
• The hallmark of cholera is severe dehydration, which can rapidly lead to hypovolemic shock, metabolic acidosis, and death if not treated.
• On dark-field microscopy of a fresh stool sample, the organisms exhibit a characteristic "darting motility".
• The mainstay of therapy is rapid and aggressive rehydration, either with oral rehydration solution (ORS) for mild/moderate cases or intravenous fluids for severe dehydration.
• Antibiotics (e.g., Doxycycline, Azithromycin) can shorten the duration of diarrhea and reduce fluid requirements but are secondary to rehydration.
• Prevention relies on sanitation, clean water access, and vaccination.

HIGH-YIELD COMPARISONS FOR EXAMS

• S. aureus vs. Coagulase-Negative Staph (CONS): S. aureus is coagulase-positive and causes pyogenic infections (abscesses, osteomyelitis), while CONS are coagulase-negative, produce a slime layer, and are a primary cause of foreign body/catheter-related infections.

• Pneumococcal Vaccines (PCV vs. PPSV): PCV (conjugate) is effective in infants <2 years, induces T-cell dependent immune memory, and provides herd immunity. PPSV (polysaccharide) is for >2 years, provides T-cell independent immunity without memory, and does not provide herd immunity.

• Group A Strep (GAS) vs. Group B Strep (GBS): GAS causes pharyngitis and skin infections in children/adults with post-infectious sequelae like Rheumatic Fever and AGN. GBS is a leading cause of neonatal sepsis and meningitis, acquired from the maternal genital tract.

• Early-onset vs. Late-onset GBS Disease: Early-onset occurs <7 days of life, typically presents as sepsis/pneumonia, is acquired vertically from the mother, and has a higher mortality rate. Late-onset occurs ≥7 days, often presents as meningitis, and is acquired from the environment.

• Scarlet Fever vs. Kawasaki Disease: Both can present with a strawberry tongue and rash. Scarlet fever is caused by GAS, has a sandpaper rash, and resolves with antibiotics. Kawasaki disease is an idiopathic vasculitis, features a polymorphous rash, conjunctivitis, and requires IVIG/aspirin to prevent coronary artery aneurysms.

• Rheumatic Fever Carditis vs. Endocarditis from S. aureus: RF carditis is a non-suppurative, post-infectious (GAS) pancarditis, often leading to chronic valvular stenosis years later. S. aureus endocarditis is an acute, destructive, suppurative infection of the heart valves, often from bacteremia.

• Pharyngeal Diphtheria vs. Hib Epiglottitis: Both cause airway obstruction. Diphtheria features a grayish, adherent pseudomembrane that bleeds when scraped, hoarseness, and a "bull-neck" appearance. Epiglottitis has a rapid onset, drooling, tripod positioning, and a "cherry-red" epiglottis on visualization.

• Staphylococcal TSS vs. Streptococcal TSS (GAS): Staph TSS is often associated with tampons, bacteremia is uncommon, and the rash is a diffuse erythema. Strep TSS is almost always associated with a soft-tissue infection (e.g., necrotizing fasciitis), bacteremia is common, and it has a higher mortality rate.

• Meningitis Triad (S. pneumoniae, N. meningitidis, Hib): All cause fever, nuchal rigidity, and altered mental status. Distinguishing clues include: S. pneumoniae (G+ diplococci) associated with pneumonia/otitis; N. meningitidis (G- diplococci) associated with a petechial/purpuric rash; Hib (G- coccobacilli) associated with epiglottitis or buccal cellulitis.

• Nontyphoidal Salmonella vs. Typhoid Fever (S. typhi): Nontyphoidal salmonellosis is a zoonosis causing self-limited gastroenteritis. Typhoid fever is a human-only disease causing a systemic febrile illness with bacteremia, rose spots, and requires mandatory antibiotic treatment.

• Shigella vs. Shiga Toxin-producing E. coli (STEC): Both can cause bloody diarrhea and HUS. Shigella infection (dysentery) is typically accompanied by high fever and is invasive. STEC infection (hemorrhagic colitis) classically has little to no fever.

• Invasive vs. Toxin-Mediated Diarrhea: Invasive diarrhea (Shigella, EIEC, Campylobacter) involves bacterial invasion of the gut mucosa, resulting in inflammation, fever, and fecal leukocytes/blood (dysentery). Toxin-mediated diarrhea (V. cholerae, ETEC) involves enterotoxins that cause fluid secretion without invasion, resulting in profuse watery diarrhea with no fever or fecal leukocytes.

QA

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GRAM-POSITIVE BACTERIA

STAPHYLOCOCCUS

1. What is the Gram stain appearance of Staphylococcus species? | Gram-positive cocci in pairs and clusters.
2. Is Staphylococcus aureus coagulase-positive or negative? | Coagulase-positive.
3. What are the species of Coagulase-negative Staphylococcus (CONS)? | S. epidermidis,
   S. saprophyticus,
   and S. haemolyticus.
4. When is a blood culture with an Antimicrobial Removal Device (ARD) ordered? | When a patient is already on antimicrobials.
5. In blood cultures, what does growth from only one of two sites often suggest? | Contamination with coagulase-negative skin flora.

1. Staphylococcus aureus

6. Where is S. aureus found as a component of normal flora? | Humans, fomites, and in dust.
7. S. aureus is the most common cause of what type of infection? | Pyogenic skin & soft tissue infection.
8. What is common with S. aureus infections? | Bacteremia.
9. What causes tissue invasion and injury from S. aureus? | Its toxins and enzymes.
10. What is the hallmark of an S. aureus infection? | Abscess formation.
11. How is S. aureus primarily transmitted? | Direct contact and auto-inoculation.
12. S. aureus is the most important cause of what infections in newborns? | Neonatal infections.
13. In children, S. aureus is the most common cause of what two conditions? | Osteomyelitis and suppurative arthritis.
14. S. aureus is a common cause of what acute heart condition? | Acute endocarditis.
15. S. aureus is the most common cause of what type of abscesses, which are usually hematogenous? | Renal & perinephric abscesses.
16. S. aureus is the principal cause of what syndrome? | Toxic Shock Syndrome (TSS).
17. Individuals with what skin condition are more susceptible to secondary staphylococcal infections? | Atopic skin.
18. Popping a pimple can lead to what three systemic S. aureus infections? | Osteomyelitis,
    infective endocarditis,
    or septic arthritis.
19. What does MRSA stand for? | Methicillin-Resistant Staphylococcus aureus.

S. aureus - Pathogenesis

20. Which S. aureus enterotoxins are associated with food poisoning? | Enterotoxins A, B, C1, C2, D, and E.
21. Which S. aureus toxins cause Staphylococcal Scalded Skin Syndrome (SSSS)? | Exfoliative toxins A and B.
22. Which S. aureus toxin is responsible for Toxic Shock Syndrome? | Toxic Shock Syndrome Toxin-1 (TSST-1).

S. aureus - Clinical Manifestations

23. What are some of the wide range of infections S. aureus can cause? | Pneumonia, sepsis, osteomyelitis, meningitis, acute endocarditis, Toxic Shock Syndrome, and food poisoning.
24. In an immunocompromised individual, what can S. aureus cause? | Lobar pneumonia.

S. aureus - Diagnosis

25. How is a diagnosis of S. aureus infection made? | By isolating the organism from normally nonpermissive sites.
26. What does laboratory diagnosis of S. aureus involve? | Gram staining, and testing for Coagulase, clumping factor, or Protein A reactivity.

S. aureus - Treatment

27. What is the initial empiric therapy for a non-life-threatening S. aureus infection? | Oxacillin.
28. What is the initial empiric therapy for a life-threatening S. aureus infection? | Vancomycin.
29. For suspected MRSA, what is considered, and what is used for CNS involvement? | Clindamycin;
    for CNS involvement, vancomycin or linezolid.
30. What are the oral options for less serious Methicillin-Susceptible S. aureus (MSSA) infections? | Dicloxacillin, Cefalexin, or Amoxicillin-Clavulanate.
31. A common side effect of vancomycin is what? | Red Man Syndrome.
32. Why is Dicloxacillin not recommended for dermatologic use, and what are preferred alternatives? | Poor bioavailability;
    cefalexin or amoxicillin-clavulanate.
33. Treatment for Initial Empiric Therapy of S. Aureus? | Non-life-threatening: Oxacillin
    Life-threatening: Vancomycin.
34. Treatment for MSSA (Penicillin-Resistant)? | Nafcillin or Oxacillin IV.
35. Treatment for MRSA? | Community-Acquired: Clindamycin, TMP-SMX
    Hospital-Acquired/Life-threatening: Vancomycin, Linezolid.
36. Treatment for VISA or VRSA? | Linezolid, Daptomycin, TMP-SMX.
37. Treatment for Less Serious MSSA? | Oral Dicloxacillin, Cefalexin, or Amoxicillin-Clavulanate.

Toxic Shock Syndrome (TSS)

38. What causes Toxic Shock Syndrome (TSS)? | TSST-1 producing strains of S. aureus.
39. What is TSS commonly associated with? | Menstruating women using tampons.
40. How does TSST-1 lead to shock? | It causes massive fluid loss from the intravascular space.

TSS - Treatment

41. What is the treatment for non-life-threatening TSS? | Nafcillin, Oxacillin, or a 1st generation Cephalosporin.
42. What is the treatment for life-threatening TSS? | Vancomycin.

2. Coagulase-Negative Staphylococcus (CONS)

43. Where are CONS normal inhabitants in the human body? | Skin, throat, mouth, vagina, and urethra.
44. What is the most common species of CONS? | S. epidermidis.
45. What do CONS produce that helps them adhere to surfaces like catheters? | A slime layer.
46. CONS are most commonly associated with what type of infections? | Catheter infections.

CONS - Clinical Manifestations

47. How can CONS infections manifest? | Bacteremia, endocarditis, infections of CSF shunts, and urinary tract infections.

CONS - Treatment

48. Are most CONS resistant to Methicillin? | Yes, functionally considered MRSA.
49. What is the drug of choice for CONS infections? | Vancomycin.

STREPTOCOCCUS

1. Streptococcus pneumoniae (Pneumococcus)

50. Describe S. pneumoniae. | A Gram-positive, lancet-shaped, polysaccharide-encapsulated diplococcus.
51. Where is S. pneumoniae a common inhabitant? | The human respiratory tract.
52. What is an important pathogenicity factor for S. pneumoniae? | The polysaccharide capsule.
53. How is S. pneumoniae transmitted? | Via respiratory droplets.
54. S. pneumoniae is the most frequent cause of what three conditions? | Bacteremia,
    bacterial pneumonia,
    and otitis media.
55. S. pneumoniae is the second most common cause of what? | Bacterial meningitis.
56. In which age groups is S. pneumoniae the most common cause of pneumonia? | Children and older adults.

S. pneumoniae - Clinical Manifestations

57. What clinical syndromes are caused by S. pneumoniae? | Otitis media, sinusitis, pneumonia, and sepsis.

S. pneumoniae - Diagnosis

58. How is a diagnosis of S. pneumoniae confirmed, and what is its appearance on Gram stain? | By isolating the organism from sterile sites; appears as lancet-shaped diplococci.

S. pneumoniae - Treatment

59. What is the treatment for penicillin-susceptible meningitis caused by S. pneumoniae? | Penicillin, Cefotaxime, or Ceftriaxone.
60. What is the treatment for penicillin-nonsusceptible meningitis by S. pneumoniae? | A combination of Vancomycin and high-dose Cefotaxime or Ceftriaxone.
61. What is the treatment for invasive pneumococcal infections outside the CNS? | High-dose Cefotaxime or Ceftriaxone.
62. What are the alternatives for S. pneumoniae treatment in patients with a penicillin allergy? | Clindamycin, Erythromycin, or TMP-SMX.

S. pneumoniae - Prognosis

63. What is the mortality rate for pneumococcal meningitis? | 10%.
64. What are the neurologic sequelae of pneumococcal meningitis? | Sensorineural hearing loss (20-30%), intellectual deficits, blindness, and paralysis.

S. pneumoniae - Prevention

65. What are the two main types of pneumococcal vaccines available? | PPSV23 (polysaccharide) and PCV13/PCV20 (conjugate).
66. Why can't PPSV23 be given to children younger than 2, and what does it not induce? | It cannot be given; it does not induce immune memory.
67. To whom can PCV13 be given, and what does it induce? | Infants; it induces immune memory and herd immunity.
68. What is the recommended childhood vaccination schedule for the pneumococcal vaccine? | At 6, 10, and 14 weeks, with a booster at 1 year old.
69. What prophylaxis is used for high-risk children (e.g., post-splenectomy)? | Daily oral Penicillin V or monthly IM Benzathine Penicillin G.

2. Group A Streptococcus (GAS) / Streptococcus pyogenes

70. Describe Group A Streptococcus (S. pyogenes). | Gram-positive cocci that grow in chains.
71. What is the natural reservoir for GAS? | Humans.
72. Virulence of GAS is primarily due to what two factors? | M protein and erythrogenic toxins.

GAS - Clinical Manifestations

73. What respiratory tract infections does GAS cause? | Acute pharyngitis and pneumonia.
74. What skin infections does GAS cause? | Impetigo and erysipelas.
75. Why is 10-day treatment crucial for untreated GAS pharyngitis? | To prevent cardiac complications.
76. What are the characteristic features of Scarlet fever? | "Sandpaper" rash,
    strawberry tongue,
    and Pastia's lines.
77. What are examples of severe invasive GAS diseases? | GAS Toxic Shock Syndrome and GAS necrotizing fasciitis.

GAS - Diagnosis

78. How is a GAS infection diagnosed? | By culture (e.g., throat swab).
79. What streptococcal antibody titers can provide evidence of a recent GAS infection? | Antistreptolysin O (ASO) titer and Anti-DNase B.

GAS - Treatment

80. What is the drug of choice for GAS pharyngitis and for how long? | Penicillin for 10 days.
81. For GAS patients with poor compliance, what can be used? | A single IM dose of Benzathine penicillin G.
82. What are the alternatives to penicillin for GAS treatment? | Amoxicillin, Cephalosporins, Clindamycin, and Macrolides.

GAS - Complications

83. How are complications of GAS infections categorized? | As suppurative or non-suppurative.
84. What are the two major non-suppurative complications of GAS? | Acute Rheumatic Fever (ARF) and Post-streptococcal Acute Glomerulonephritis (AGN).
85. When may Acute Glomerulonephritis occur after a primary GAS infection? | 2 weeks to 1 month.

Rheumatic Fever

Rheumatic Fever - Pathogenesis

86. What is the immunologic theory of ARF pathogenesis? | GAS components (like M protein) share antigens with human tissues, leading to cross-reactivity.
87. What is the cytotoxic theory of ARF pathogenesis? | Enzymes from GAS are directly toxic to cardiac cells.

Rheumatic Fever - Jones Criteria

88. On what is the diagnosis of Acute Rheumatic Fever based? | Jones Criteria: 2 major OR 1 major and 2 minor criteria.
89. What are the major criteria for ARF? | (JONES)
    Joints (migratory polyarthritis),
    O (carditis),
    Nodules (subcutaneous),
    Erythema marginatum,
    Sydenham chorea.
90. What is the most serious manifestation of ARF? | Carditis, with valvulitis being a universal finding.
91. What is migratory polyarthritis in ARF? | Affects large joints and often has an inverse relationship with the severity of carditis.
92. What is chorea in ARF? | A late manifestation with emotional lability and uncontrollable movements.
93. What is Erythema marginatum in ARF? | A non-pruritic, serpiginous rash with pale centers.
94. What are subcutaneous nodules in ARF? | Firm, painless nodules found over bony prominences.
95. What are the minor criteria for ARF? | Fever, arthralgia, elevated acute phase reactants (ESR, CRP), and a prolonged PR interval.
96. When can an ARF diagnosis be made without meeting full Jones criteria? | In cases of pure chorea, indolent carditis, or recurrent ARF.

Rheumatic Fever - Treatment

97. What antibiotic therapy is given to eradicate GAS in ARF? | Penicillin for 10 days or a single dose of Benzathine penicillin IM.
98. What anti-inflammatory therapy is used for ARF? | Aspirin for arthritis/mild carditis, or corticosteroids (Prednisone) for severe carditis.
99. What is the drug of choice for managing chorea in ARF? | Phenobarbital.

Rheumatic Fever - Prognosis & Prevention

100. The long-term sequelae of ARF are usually limited to what organ? | The heart (rheumatic heart disease).
101. What does the prognosis of ARF depend on? | The severity of the initial cardiac involvement.
102. What does primary prevention of ARF involve? | Treating GAS pharyngitis promptly with antibiotics.
103. What does secondary prevention of ARF involve? | Continuous antibiotic prophylaxis (e.g., monthly Benzathine penicillin G).
104. The duration of secondary prophylaxis for ARF depends on what? | The presence and severity of residual heart disease.

3. Group B Streptococcus (GBS) / Streptococcus agalactiae

105. Describe Group B Streptococcus (S. agalactiae). | Anaerobic Gram-positive cocci in chains or pairs.
106. GBS virulence is attributed to what? | Its polysaccharide capsule, surface proteins, and enzymes.
107. GBS is a common etiologic agent of neonatal sepsis along with what two other organisms? | E.coli and Listeria monocytogenes.
108. Describe early-onset GBS disease. | Occurs within 7 days of life, presents as sepsis or pneumonia, high fatality.
109. Describe late-onset GBS disease. | Occurs after 7 days, presents as meningitis, acquired from environment/community.
110. Name three maternal risk factors for early-onset GBS disease. | GBS colonization,
     previous infant with GBS disease,
     PROM > 18 hours,
     intrapartum fever.

GBS - Diagnosis

111. How is a diagnosis of GBS made? | By isolating and identifying GBS from normally sterile sites (blood, urine, CSF).
112. What are some lab findings in GBS disease? | Neutropenia/neutrophilia, increased bands, leukopenia, and elevated CRP.

GBS - Treatment

113. What is the initial empiric treatment for suspected neonatal sepsis? | A combination of Ampicillin and an Aminoglycoside.
114. What is the drug of choice for a confirmed GBS infection? | Penicillin G.

GBS - Prevention

115. How is GBS prevented, and when are pregnant women screened? | Chemoprophylaxis;
     screened at 35-37 weeks of gestation.
116. What intrapartum antibiotic prophylaxis is given to GBS-positive mothers? | Penicillin as the drug of choice.

ENTEROCOCCUS

117. Describe Enterococcus species. | Gram-positive facultative anaerobes in pairs or short chains.
118. Enterococcus is a common cause of what type of infections? | Hospital-acquired infections.
119. Which Enterococcus species accounts for about 80% of infections? | E. faecalis.
120. Compare early-onset vs. late-onset neonatal Enterococcus sepsis. | Early-onset <7 days;
     late-onset ≥7 days with higher mortality.
121. In older children, Enterococcus is a cause of what? | Nosocomial urinary tract infections (15%).

Enterococcus - Treatment

122. What is the treatment for minor Enterococcus infections in immunocompetent patients? | Ampicillin.
123. What is an option for uncomplicated UTIs caused by Enterococcus? | Nitrofurantoin.
124. What is used for invasive Enterococcus infections like sepsis or endocarditis? | A synergistic combination of Penicillin/Ampicillin and an aminoglycoside.

CORYNEBACTERIUM DIPHTHERIAE

125. What is Corynebacterium diphtheriae and what disease does it cause? | An aerobic, Gram-positive bacillus that causes diphtheria.
126. What is the appearance of C. diphtheriae on Gram stain? | Club-shaped bacilli, sometimes in a palisading arrangement.
127. Where is the exclusive habitat of C. diphtheriae? | Human mucous membranes and skin.
128. What makes a C. diphtheriae strain toxigenic and able to cause severe disease? | Lysogenization by a bacteriophage carrying the tox gene.

C. diphtheriae - Pathogenesis

129. How does the diphtheria exotoxin cause damage? | Inhibits cellular protein synthesis, causing destruction and pseudomembrane formation.
130. How does the diphtheria toxin cause systemic effects? | It is absorbed into the bloodstream.
131. What can non-toxigenic strains of C. diphtheriae cause? | Mild pharyngitis without a pseudomembrane.
132. How is diphtheria transmitted? | Via airborne respiratory droplets or direct contact with secretions.

C. diphtheriae - Clinical Features

133. What is the incubation period for diphtheria? | 2-4 days.
134. Describe the pseudomembrane seen in Pharyngeal and Tonsillar Diphtheria. | An adherent, grayish-green membrane that bleeds on forceful removal.
135. What causes the "bull-neck" appearance in diphtheria? | Significant soft tissue edema.
136. What are the symptoms of Laryngeal Diphtheria? | Hoarseness and a barking cough.
137. Describe Anterior Nasal Diphtheria. | A milder form with a serosanguineous discharge and a white nasal membrane.
138. How does Cutaneous Diphtheria appear? | As nonhealing ulcers with a gray-brown membrane.

C. diphtheriae - Complications

139. What are the most frequent and severe complications of diphtheria? | Myocarditis and neuritis, attributable to the toxin.
140. Toxic cardiomyopathy from diphtheria accounts for how many deaths? | 50-60%.
141. What can toxic neuropathy from diphtheria cause? | Paralysis of the soft palate and other neuropathies.

C. diphtheriae - Diagnosis & Treatment

142. How is a diagnosis of diphtheria made? | By culture of the lesion.
143. What is the mainstay of therapy for diphtheria? | Equine Diphtheria antitoxin.
144. Why are antibiotics given in diphtheria treatment? | To halt toxin production and prevent transmission.

C. diphtheriae - Prevention

145. What precautions are required for diphtheria patients? | Droplet precautions (pharyngeal) or contact precautions (cutaneous).
146. What prophylaxis should close contacts of a diphtheria patient receive? | Erythromycin or Benzathine penicillin G.
147. What is the most effective means of preventing diphtheria? | Vaccination with the Diphtheria toxoid.

LISTERIA MONOCYTOGENES

148. Describe Listeria monocytogenes. | A facultative anaerobic, motile, Gram-positive bacillus that is an intracellular pathogen.
149. How is listeriosis transmitted and what foods are linked to it? | Food-borne illness; aged soft cheeses, unpasteurized milk, ready-to-eat meats.
150. In what populations is listeriosis most common? | The extremes of age (newborns and elderly) and the immunosuppressed.
151. In pregnancy, what can listeriosis cause in the mother and fetus? | A flu-like illness in the mother, potentially seeding uterine contents.

L. monocytogenes - Manifestations

152. Describe early-onset neonatal listeriosis. | <5 days, acquired in utero, multisystem disease, high mortality rate (>30%).
153. Describe late-onset neonatal listeriosis. | ≥5 days, acquired after birth, presents as meningitis.
154. In older children and adults, who does listeriosis usually affect and what does it cause? | Immunosuppressed; causes meningitis or sepsis.

L. monocytogenes - Diagnosis & Treatment

155. How is a diagnosis of listeriosis confirmed? | By culture from blood or CSF.
156. What is the treatment for listeriosis? | Ampicillin, often with an Aminoglycoside for synergy.
157. What are the alternative treatments for listeriosis? | Vancomycin or TMP-SMX.

GRAM-NEGATIVE BACTERIA

NEISSERIA MENINGITIDIS (Meningococcus)

158. Describe Neisseria meningitidis. | A fastidious, encapsulated, aerobic Gram-negative diplococcus.
159. N. meningitidis is a major cause of what two conditions? | Meningitis and sepsis (meningococcemia).
160. Which serogroups of N. meningitidis cause most invasive disease? | A, B, C, Y, and W-135.
161. How is N. meningitidis transmitted? | Through aerosol droplets and contact with respiratory secretions.
162. How does the pathogenesis of N. meningitidis begin? | With nasopharyngeal colonization, followed by bloodstream invasion.

N. meningitidis - Clinical Manifestations

163. What is meningococcemia? | The dissemination of N. meningitidis into the bloodstream.
164. What is the clinical case definition for meningococcal disease? | Sudden high fever plus neck stiffness, altered consciousness, or a non-blanching rash.
165. What is the hallmark of acute meningococcemia? | Fever with a non-blanching rash (petechiae, purpura).
166. What is Purpura fulminans? | A severe form of meningococcemia with widespread purpura, septic shock, and DIC.
167. What is the most common clinical manifestation of meningococcal disease? | Meningitis with meningococcemia (40% of cases).
168. What is Waterhouse-Friderichsen Syndrome? | A devastating complication with diffuse adrenal hemorrhage.
169. What are poor prognostic signs in meningococcal disease? | Petechiae <12 hours, absence of meningitis, low or normal ESR.
170. What is the most frequent neurologic sequela of meningococcal meningitis? | Deafness (5-10% of cases).

N. meningitidis - Diagnosis

171. What is the gold standard for diagnosing meningococcal disease? | Isolation of the organism from blood, CSF, or petechial lesions.
172. How can a rapid presumptive diagnosis of meningococcal disease be made? | Gram stain of a skin lesion aspirate showing Gram-negative diplococci.
173. What is a limitation of rapid latex agglutination tests on CSF for N. meningitidis? | May have false negatives.

N. meningitidis - Treatment

174. What is the empiric treatment for suspected meningococcal disease? | A third-generation cephalosporin (e.g., Ceftriaxone or Cefotaxime).
175. Patients with meningococcal disease should be placed on what precautions? | Droplet precautions for 24 hours after starting antibiotics.

N. meningitidis - Prevention and Chemoprophylaxis

176. Who is indicated for antibiotic prophylaxis for N. meningitidis? | Close contacts exposed to secretions within 7 days before illness onset.
177. What are the prophylactic drugs for N. meningitidis contacts? | Rifampin, Ceftriaxone, or Ciprofloxacin.
178. Vaccination is available against which serogroups of N. meningitidis? | A, C, Y, W-135 (MenACWY conjugate vaccine) and separately for serogroup B.

HAEMOPHILUS INFLUENZAE TYPE B (Hib)

179. Describe Haemophilus influenzae. | A Gram-negative coccobacillus.
180. Which type of H. influenzae was a major cause of invasive disease before vaccination? | Type b (Hib).
181. What are the only natural hosts for H. influenzae? | Humans.
182. What type of infections do nontypeable strains of H. influenzae typically cause? | Noninvasive infections like otitis media and sinusitis.
183. Why did invasive Hib disease have a high incidence in young children? | Due to an immature immune response to its polysaccharide capsule.

Hib - Clinical Manifestations

184. What are the most common types of invasive Hib disease? | Meningitis, epiglottitis, pneumonia, arthritis, and cellulitis.
185. Why is epiglottitis (supraglottitis) a medical emergency? | Due to the risk of sudden airway obstruction.
186. Where does Hib cellulitis classically affect, and what is its appearance? | The cheek or periorbital area, with a bluish-purple discoloration.
187. What joints does Hib septic arthritis commonly affect? | Large joints like the knee, hip, or ankle.

Hib - Diagnosis & Treatment

188. How is Hib disease diagnosed? | By Gram staining and culture of specimens from sterile sites.
189. What is the drug of choice for susceptible strains of Hib? | Ampicillin.
190. What is used for invasive disease or resistant cases of Hib? | A third-generation cephalosporin (Ceftriaxone, Cefotaxime).
191. What is used for non-invasive Hib disease like otitis media? | Amoxicillin or Amoxicillin-clavulanate.

Hib - Prevention

192. Why is invasive Hib disease now rare in immunized populations? | Due to the highly effective Hib conjugate vaccine.
193. When is post-exposure prophylaxis with Rifampicin recommended for Hib? | For household contacts if there is an unimmunized or immunocompromised child.

BORDETELLA PERTUSSIS

194. What is Bordetella pertussis and what does it cause? | A small, aerobic Gram-negative coccobacillus that causes pertussis (whooping cough).
195. How is pertussis transmitted? | By aerosol droplets.
196. What is the major virulence protein of B. pertussis and what systemic effect does it cause? | Pertussis toxin (PT); causes profound lymphocytosis.

B. pertussis - Clinical Manifestations

197. What are the three stages of pertussis? | 1. Catarrhal stage (1-2 weeks)
     2. Paroxysmal stage (2-6 weeks)
     3. Convalescent stage (weeks to months).
198. How does pertussis present in infants <3 months old? | The "whoop" is often absent; presentation may be apnea, gasping, or cyanosis.
199. When should pertussis be suspected? | In any person with a cough lasting ≥14 days.
200. What is a key laboratory finding in pertussis? | Marked leukocytosis with an absolute lymphocytosis.

B. pertussis - Diagnosis & Treatment

201. What is the gold standard for diagnosing pertussis? | Culture from a nasopharyngeal swab.
202. What is the drug of choice for treating pertussis? | A macrolide, such as Azithromycin.
203. For which patients with pertussis should be hospitalized for monitoring? | Infants <3 months old.

B. pertussis - Complications & Prevention

204. What are the most common complications of pertussis? | Apnea, secondary pneumonia, and physical sequelae from coughing.
205. Does natural disease or vaccination provide lifelong immunity to pertussis? | No, neither provides lifelong immunity.
206. How is pertussis prevented? | Through vaccination with the acellular pertussis component in DTaP, Tdap vaccines.

SALMONELLA

1. Nontyphoidal Salmonellosis

207. Nontyphoidal Salmonellosis is caused by serotypes like what? | S. enteritidis and S. typhimurium.
208. How is Nontyphoidal Salmonellosis primarily transmitted? | From animal reservoirs (poultry, eggs, reptiles) via contaminated food.
209. What is the most common manifestation of Nontyphoidal Salmonellosis? | Acute enteritis (gastroenteritis).
210. Why are antibiotics generally not recommended for uncomplicated Nontyphoidal Salmonellosis? | They can prolong shedding.
211. When are antibiotics indicated for Nontyphoidal Salmonellosis? | For infants <3 months old and high-risk groups.
212. What is a major complication of Nontyphoidal Salmonellosis in patients with sickle cell disease? | Osteomyelitis.

2. Enteric Fever (Typhoid Fever)

213. What causes Enteric Fever (Typhoid Fever)? | Salmonella enterica serovar Typhi.
214. How is Typhoid Fever transmitted? | Exclusively from human carriers via the fecal-oral route.
215. What are the clinical features of Typhoid Fever? | Prolonged step-ladder fever, malaise, headache, and "rose spots" on the trunk.
216. What is the gold standard for diagnosing Typhoid Fever, and which culture is most sensitive? | Culture; bone marrow culture is most sensitive.
217. What is a limitation of the Widal test for Typhoid Fever? | Lacks sensitivity and specificity.
218. What antibiotics are used to treat Typhoid Fever? | Ceftriaxone, Azithromycin, or a fluoroquinolone.
219. When is Dexamethasone given in Typhoid Fever treatment? | To severely ill patients with shock or an altered mental state.
220. How is Typhoid Fever prevented? | Sanitation, safe water, and vaccination.

SHIGELLA

221. What do Shigella species cause? | Bacillary dysentery.
222. How is Shigella transmitted? | Fecal-oral route (very low infective dose).
223. What is the target organ for Shigella? | The colon.
224. What is the clinical presentation of shigellosis? | High fever, cramps, tenesmus, and grossly bloody and mucoid diarrhea.
225. What is a classic physical exam finding in shigellosis? | A spurt of bloody stool upon digital rectal examination.
226. What neurologic findings are common in young children with shigellosis? | Seizures.
227. What is a severe complication of shigellosis, particularly with S. dysenteriae type 1? | Hemolytic Uremic Syndrome (HUS).
228. What is the Ekiri syndrome? | A rare, rapidly fatal toxic encephalopathy associated with shigellosis.
229. How is a diagnosis of shigellosis confirmed? | Stool culture.
230. What is the treatment for shigellosis? | Supportive care and antibiotics (Ceftriaxone, Azithromycin, or Ciprofloxacin).

Diarrheagenic ESCHERICHIA COLI

231. What type of diarrhea does Enterotoxigenic E. coli (ETEC) cause, and what is it a major cause of? | Secretory, watery diarrhea; a major cause of traveler's diarrhea.
232. What type of illness does Enteroinvasive E. coli (EIEC) cause? | Inflammatory colitis with fever and bloody stools (dysentery).
233. What type of diarrhea does Enteropathogenic E. coli (EPEC) cause? | Non-bloody, mucoid, persistent diarrhea, especially in infants.
234. What illness does Shiga toxin-producing E. coli (STEC/EHEC) cause and is fever common? | Hemorrhagic colitis (bloody diarrhea); fever is uncommon.
235. What is the adherence pattern and resulting diarrhea of Enteroaggregative E. coli (EAEC)? | "Stacked brick" pattern; causes persistent, secretory diarrhea.
236. Why are antibiotics generally not recommended for diarrheagenic E. coli, especially STEC? | May increase HUS risk.

VIBRIO CHOLERAE

237. What is Vibrio cholerae and what does it cause? | A Gram-negative, comma-shaped bacillus that causes cholera.
238. How is cholera transmitted? | Via contaminated water or undercooked shellfish.
239. What does cholera toxin cause? | Massive, cAMP-mediated secretion of chloride and water.
240. What is the characteristic description of stools in cholera? | "Rice-water stools" with a fishy odor.
241. What is the hallmark of cholera? | Severe dehydration.
242. What is the characteristic motility of V. cholerae on dark-field microscopy? | "Darting motility".
243. What is the mainstay of therapy for cholera? | Rapid and aggressive rehydration (ORS or intravenous fluids).
244. What is the role of antibiotics in cholera treatment? | Secondary to rehydration; can shorten the duration of diarrhea.

HIGH-YIELD COMPARISONS FOR EXAMS

245. Compare S. aureus vs. Coagulase-Negative Staph (CONS). | S. aureus: Coagulase-positive, pyogenic infections (abscesses).
     CONS: Coagulase-negative, slime layer, foreign body/catheter infections.
246. Compare pneumococcal vaccines PCV vs. PPSV. | PCV: For infants <2y, induces memory, provides herd immunity.
     PPSV: For >2y, no memory, no herd immunity.
247. Compare Group A Strep (GAS) vs. Group B Strep (GBS). | GAS: Causes pharyngitis/skin infections, post-infectious sequelae (ARF, AGN).
     GBS: A leading cause of neonatal sepsis and meningitis.
248. Compare Early-onset vs. Late-onset GBS Disease. | Early-onset: <7 days, sepsis/pneumonia, vertical transmission, higher mortality.
     Late-onset: >7 days, meningitis, environmental acquisition.
249. Compare Scarlet Fever vs. Kawasaki Disease. | Scarlet Fever: Caused by GAS, sandpaper rash, responds to antibiotics.
     Kawasaki: Idiopathic vasculitis, polymorphous rash, requires IVIG/aspirin.
250. Compare Rheumatic Fever Carditis vs. Endocarditis from S. aureus. | RF Carditis: Non-suppurative, post-GAS, chronic valvular disease.
     S. aureus Endocarditis: Acute, destructive, suppurative valve infection.
251. Compare Pharyngeal Diphtheria vs. Hib Epiglottitis. | Diphtheria: Gray pseudomembrane that bleeds, "bull-neck".
     Epiglottitis: Rapid onset, drooling, tripod position, "cherry-red" epiglottis.
252. Compare Staphylococcal TSS vs. Streptococcal TSS (GAS). | Staph TSS: Tampon-associated, bacteremia uncommon, diffuse erythema.
     Strep TSS: Associated with soft-tissue infection, bacteremia common, higher mortality.
253. Differentiate the causes of the Meningitis Triad (S. pneumoniae, N. meningitidis, Hib). | S. pneumoniae: G+ diplococci, associated with pneumonia/otitis.
     N. meningitidis: G- diplococci, associated with petechial rash.
     Hib: G- coccobacilli, associated with epiglottitis.
254. Compare Nontyphoidal Salmonella vs. Typhoid Fever (S. typhi). | Nontyphoidal: Zoonosis, self-limited gastroenteritis.
     Typhoid: Human-only, systemic illness, requires antibiotics.
255. Compare Shigella vs. Shiga Toxin-producing E. coli (STEC). | Shigella: Invasive, high fever, dysentery.
     STEC: Hemorrhagic colitis, little to no fever.
256. Compare Invasive vs. Toxin-Mediated Diarrhea. | Invasive: Mucosal invasion, inflammation, fever, fecal leukocytes/blood (dysentery).
     Toxin-mediated: Fluid secretion, no invasion, watery diarrhea, no fever or leukocytes.

4.2

Summary

text

CHILDHOOD TUBERCULOSIS

MYCOBACTERIUM TUBERCULOSIS (THE ORGANISM)

• In Childhood TB, Mycobacterium tuberculosis is the most important cause of TB disease in humans.
• M. tuberculosis is a non-sporeforming, non-motile, pleomorphic, weakly gram-positive, obligate aerobe.
• The hallmark of all mycobacteria is acid-fastness, which is due to a lipid-rich, waxy cell wall with high mycolic acid content.
• M. bovis is the classic zoonotic strain of TB, associated with unpasteurized milk.
• The Bacillus Calmette–Guérin (BCG) vaccine is derived from an attenuated strain of M. bovis.

PATHOGENESIS AND NATURAL HISTORY

• TB transmission occurs via inhalation of airborne droplets smaller than 5 microns.
• The primary immune response to TB involves engulfment of the antigen by alveolar macrophages, transport to hilar lymph nodes, and formation of a granuloma, which is a Type IV hypersensitivity reaction.
• Caseation necrosis refers to the "cheese-like" central cell death that occurs within a TB granuloma.
• The Primary Complex or Ghon Complex of tuberculosis includes the local infection at the portal of entry (parenchymal lung focus) and the draining regional lymph nodes.
• Disseminated TB occurs if the number of circulating bacilli is large and the host's cellular immune response is inadequate.
• A pediatric TB diagnosis acts as a sentinel event indicating recent transmission from an infectious adult, as child-to-child transmission is nearly nonexistent.
• Wallgren’s Timetable predicts when different TB manifestations appear after primary infection.
• According to Wallgren's Timetable, miliary TB and TB meningitis typically develop 2-6 months after primary infection.
• According to Wallgren's Timetable, TB adenitis or endobronchial TB typically develops 3-9 months after primary infection.
• According to Wallgren's Timetable, bone and joint TB typically develops 1 year or more after primary infection.
• According to Wallgren's Timetable, renal TB typically develops 5-25 years after primary infection.
• The three major transitions in the natural history of TB are Exposure, Infection, and Disease.

CLINICAL PRESENTATIONS (PULMONARY TB)

• The hallmark of Primary Pulmonary TB in children is the relatively large size of regional lymphadenitis compared with the small size of the initial lung focus.
• The usual radiologic sequence in Primary Pulmonary TB is hilar lymphadenopathy, followed by focal hyperinflation, and then atelectasis.
• Progressive Primary Pulmonary Disease is a rare but serious complication where the primary focus enlarges, develops a caseous center, and liquefies.
• Reactivation TB is rare in young children but can occur in adolescence (often in those >7 years old).
• The most common sites for Reactivation TB are the original parenchymal focus, lymph nodes, or the apical seedings known as Simon Foci.
• The most common radiographic findings in Reactivation TB are extensive infiltrates and thick-walled cavities in the upper lobes.

DIAGNOSIS & WORK-UP

• Presumptive TB in a child (<15 years old) is suspected if they present with 3 or more of the following: cough >2 weeks, unexplained fever >2 weeks, failure to respond to antibiotics, failure to regain health post-virus, FTT, or lethargy.
• A person is considered to have TB Exposure or to be a "close contact" if they had prolonged, frequent, or intense contact with an infectious TB patient.
• The Tuberculin Skin Test (TST or PPD) detects a delayed (Type IV) cellular hypersensitivity to TB antigens.
• The "window period" for the TST is 2-12 weeks from exposure to a detectable reaction.
• A TST result is considered positive with an induration of ≥ 5mm in children with a history of close contact, clinical findings of TB, CXR suggestive of TB, or immunocompromised status.
• Sputum collection is recommended for diagnosis in children more than 5 years old or who can expectorate.
• Two sputum specimens should be sent for microscopy: one spot and one early morning, or two specimens collected 1-2 hours apart (front-loading).
• The only contraindication to collecting sputum for DSSM is massive hemoptysis (200-600 ml in 24 hours).
• Gastric washing/aspiration is used for sputum collection in children less than 5 years old or who cannot expectorate.
• When performing gastric washing, KY jelly should not be used as a lubricant because it is bacteriostatic.
• AFB smears of gastric aspirates have low sensitivity, with positive results in fewer than 10% of cases.
• Sputum cultures of gastric aspirate specimens are positive in only 30%-40% of cases.
• Interferon Gamma Release Assays (IGRAs) should NOT be used for the diagnosis of active pulmonary or extrapulmonary TB; they only indicate TB infection (LTBI).
• The Xpert MTB/RIF assay is a fully automated, cartridge-based NAAT that can simultaneously detect TB bacteria and Rifampicin resistance in less than 2 hours.
• For a positive AFB smear, at least 5,000 to 10,000 bacilli per mL are needed, whereas a culture can be positive with only 10-100 organisms.
• The commonest chest radiologic finding in Primary TB is lymphadenopathy.
• Worsening of radiographic findings, such as enlargement of lymph nodes, can be seen in the first 3 months of anti-TB treatment and is not necessarily a sign of failure.
• Miliary (Disseminated) TB on a chest x-ray resembles millet seeds, which are small, uniformly sized nodules distributed throughout the lungs.

EXTRAPULMONARY TUBERCULOSIS (EPTB)

• EPTB accounts for 30-40% of pediatric TB cases.
• The most common forms of EPTB in children are lymphatic (adenitis), pleural, and bone TB.
• The most fatal forms of EPTB are pericardial, meningeal, and miliary TB.
• Clues to suspecting EPTB include monoarticular arthritis, persistent sterile pyuria, unexplained pericardial effusion, vertebral osteomyelitis of the thoracic spine, and chronic cervical lymphadenopathy.
• Cervical lymphadenopathy (Scrofula) is the most common form of extrapulmonary TB in children, presenting as painless, firm nodes that become matted.
• If untreated, tuberculous cervical lymphadenopathy can rupture through the skin, forming a draining sinus tract known as Scrofuloderma.
• In Cardiac TB, the main finding is pericardial involvement, often with pericardial thickening of >3mm on CT scan.
• TB Meningitis is the most common type of CNS TB and the most common cause of TB-related mortality.
• It is imperative that anti-TB treatment be considered in any child who develops basilar meningitis, hydrocephalus, cranial nerve palsies, or stroke with no other apparent etiology.
• Communicating hydrocephalus is the most common complication of CNS TB.
• Tuberculomas are intracranial space-occupying lesions that are frequently multiple.
• TB abscesses are typically solitary, larger than tuberculomas, and associated with a more accelerated clinical course.
• TB of the bones and joints is common in young children due to increased blood flow in growing bones.
• TB arthritis is typically monoarticular, most commonly affecting the hip and knee.
• The "Phemister Triad" on radiograph for TB arthritis consists of: juxta-articular osteoporosis, peripherally located osseous erosions, and gradual narrowing of the joint space.
• TB of the Spine (Pott's disease) most commonly affects the lower thoracic and upper lumbar vertebrae.
• A "gibbus" deformity is a characteristic physical exam finding in Pott's disease.
• Peritonitis is the most common clinical manifestation of abdominal TB.
• The ileocecal region is involved in 80-90% of gastrointestinal TB cases.
• The Fleischner sign in GI TB is the thickening of ileocecal valve lips or a wide gaping valve with narrowing of the terminal ileum.
• Disseminated TB is defined as the involvement of two or more organ systems.

TREATMENT OF TUBERCULOSIS

• Isoniazid Preventive Therapy (IPT) is given for six (6) months to asymptomatic children less than five (5) years old who are household contacts of a confirmed TB case.
• The standard dose for INH in Isoniazid Preventive Therapy (IPT) is 10 mg/kg.
• The standard 6-month regimen for new, drug-susceptible TB (pulmonary and most EPTB) is 2 months of HRZE (intensive phase) followed by 4 months of HR (continuation phase).
• Treatment for TB meningitis or TB of the bones and joints is extended to a total of 10-12 months.
• Standard pediatric dosages for first-line anti-TB drugs are: Isoniazid (H) 10 mg/kg, Rifampicin (R) 15 mg/kg, Pyrazinamide (Z) 25-30 mg/kg, and Ethambutol (E) 20 mg/kg.
• A patient with clinically diagnosed TB is considered non-contagious after one week of uninterrupted treatment.
• A patient with bacteriologically confirmed TB is considered non-contagious after a negative follow-up sputum smear microscopy (DSSM).
• Follow-up of treatment response is done with sputum smear microscopy (DSSM), not the Xpert MTB/RIF test, because Xpert cannot differentiate between live and dead bacilli.
• All first-line anti-TB drugs are hepatotoxic, with the relative risk being Pyrazinamide > INH > Rifampicin.
• Isoniazid can cause peripheral neuropathy, which is prevented by co-administering Pyridoxine (Vitamin B6).
• Ethambutol can cause optic neuritis, leading to decreased visual acuity and color blindness.
• Drug-Induced Liver Injury (DILI) is defined as an AST level >3x the upper limit of normal with symptoms, or >5x the upper limit without symptoms.
• If a patient on TB treatment develops jaundice, all hepatotoxic drugs must be stopped.
• After DILI resolves (AST <2x ULN), TB drugs are restarted sequentially: Rifampicin first, then INH, then Pyrazinamide.
• Adjunctive steroid therapy (Prednisone) is indicated for TB meningitis, TB pericarditis, endobronchial TB, and severe miliary TB.

DRUG-RESISTANT TB

• The Philippines has a high prevalence of Isoniazid (INH) resistance.
• MDR-TB (Multi-Drug Resistant TB) is defined as TB resistant to at least INH and Rifampicin.
• In the Philippines, if a GeneXpert result is "Rifampicin-Resistant," the case is already considered MDR-TB.
• XDR-TB (Extensively Drug-Resistant TB) is MDR-TB with additional resistance to any fluoroquinolone AND any second-line injectable agent (amikacin, kanamycin, capreomycin).
• Suspects for MDR-TB include patients who fail treatment regimens, relapse cases, and contacts of known MDR-TB patients.

SPECIAL SITUATIONS IN TB

• The presentation of TB disease in a child is a significant indicator of recent and ongoing transmission of M. tuberculosis within the community.
• Congenital TB is rare. The most common route of TB transmission to a newborn is postnatal airborne transmission from an adult with active pulmonary TB.
• A newborn of a mother with LTBI is not separated at birth and can be given BCG.
• A newborn of a mother with active TB disease should be isolated if the mother has been on anti-TB treatment for less than 2 weeks.

HIGH-YIELD COMPARISONS FOR EXAMS

• TB Exposure vs. TB Infection (LTBI) vs. TB Disease:

  • Exposure: Contact with a TB case, but has a negative TST, no symptoms, and a normal CXR.
  • Infection (LTBI): Has a positive TST (or IGRA) indicating an immune response, but has no symptoms and a normal CXR. The bacteria are dormant.
  • Disease: The bacteria are actively multiplying. The patient has symptoms, may have an abnormal CXR, and may have a positive bacteriological test (e.g., sputum smear, Xpert).

• Primary TB vs. Reactivation TB (in children/adolescents):

  • Primary TB: Occurs shortly after initial infection. The radiographic hallmark in children is prominent hilar or mediastinal lymphadenopathy, often with a small, inconspicuous lung focus (Ghon complex).
  • Reactivation TB: Reactivation of a latent infection, more common in adolescents. The classic radiographic finding is upper lobe/apical infiltrates with cavitation.

• TST/IGRA vs. Xpert MTB/RIF for Diagnosis:

  • TST/IGRA: These are immunologic tests that detect an immune response to M. tuberculosis. They CANNOT distinguish between latent infection (LTBI) and active disease.
  • Xpert MTB/RIF: This is a molecular test (NAAT) that detects the DNA of the bacteria. It is used to diagnose ACTIVE TB disease and provides rapid information on Rifampicin resistance.

• Sputum Collection vs. Gastric Washing:

  • Sputum Collection: The preferred method for patients who can voluntarily cough up and expectorate sputum, typically children older than 5 years.
  • Gastric Washing: An alternative for infants and young children (<5 years) who cannot expectorate. It involves aspirating swallowed respiratory secretions from the stomach.

• Cervical Lymphadenopathy (Scrofula) vs. Scrofuloderma:

  • Scrofula: Refers to TB infection of the cervical lymph nodes, presenting as a firm, non-tender mass.
  • Scrofuloderma: A complication of untreated scrofula where the infected lymph node caseates, liquefies, and ruptures through the overlying skin, creating a chronic draining sinus tract.

• Tuberculoma vs. TB Abscess (in CNS):

  • Tuberculoma: A solid or semi-solid mass of caseous material in the brain, often behaving like a tumor. They are frequently multiple.
  • TB Abscess: A true liquid pus-filled cavity in the brain. They are typically solitary, larger than tuberculomas, and are associated with a more rapid and severe clinical course.

• MDR-TB vs. XDR-TB:

  • MDR-TB (Multi-Drug Resistant): Resistant to AT LEAST the two most important first-line drugs: Isoniazid (INH) and Rifampicin (RMP).
  • XDR-TB (Extensively Drug-Resistant): MDR-TB with additional resistance to any fluoroquinolone AND at least one of the three second-line injectable drugs (e.g., amikacin, capreomycin).

• Child vs. Adult Transmission Dynamics:

  • Children: Typically have paucibacillary (low bacterial load) disease without cavitary lesions, making child-to-child transmission extremely rare.
  • Adults: Often have cavitary, multibacillary (high bacterial load) disease, making them the primary source of infection for children and the community.

• Phemister's Triad vs. Pott's Disease:

  • Phemister's Triad: Radiographic findings for tuberculous arthritis (joint infection), consisting of juxta-articular osteoporosis, peripheral erosions, and gradual joint space narrowing.
  • Pott's Disease: Refers specifically to TB of the spine (vertebral infection), which can lead to vertebral collapse and a characteristic "gibbus" deformity.

• Most Common vs. Most Fatal EPTB:

  • Most Common EPTB: In children, the most frequent forms are Lymphatic (scrofula), Pleural, and Bone/Joint TB.
  • Most Fatal EPTB: The forms with the highest mortality are Pericardial, Meningeal (TB Meningitis), and Miliary (Disseminated) TB.

QA

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MYCOBACTERIUM TUBERCULOSIS (THE ORGANISM)

1. In Childhood TB, what is the most important cause of TB disease in humans? | Mycobacterium tuberculosis
2. What are the characteristics (5) of M. tuberculosis? | Non-sporeforming
   Non-motile
   Pleomorphic
   Weakly gram-positive
   Obligate aerobe
3. What is the hallmark of all mycobacteria, and what is its cause? | Acid-fastness; due to a lipid-rich, waxy cell wall with high mycolic acid content.
4. What is the classic zoonotic strain of TB, and with what is it associated? | M. bovis; associated with unpasteurized milk.
5. The Bacillus Calmette–Guérin (BCG) vaccine is derived from an attenuated strain of what organism? | M. bovis

PATHOGENESIS AND NATURAL HISTORY

6. How does TB transmission occur? | Via inhalation of airborne droplets smaller than 5 microns.
7. The primary immune response to TB, including granuloma formation, is what type of hypersensitivity reaction? | Type IV hypersensitivity reaction.
8. What term refers to the "cheese-like" central cell death seen within a TB granuloma? | Caseation necrosis.
9. What are the two components of the Primary Complex or Ghon Complex of tuberculosis? | Parenchymal lung focus
   Draining regional lymph nodes.
10. Under what conditions does Disseminated TB occur? | Large number of circulating bacilli and an inadequate host cellular immune response.
11. A pediatric TB diagnosis acts as a sentinel event indicating what? | Recent transmission from an infectious adult.
12. What timetable predicts when different TB manifestations appear after primary infection? | Wallgren’s Timetable.
13. According to Wallgren's Timetable, when do miliary TB and TB meningitis typically develop? | 2-6 months after primary infection.
14. According to Wallgren's Timetable, when do TB adenitis or endobronchial TB typically develop? | 3-9 months after primary infection.
15. According to Wallgren's Timetable, when does bone and joint TB typically develop? | 1 year or more after primary infection.
16. According to Wallgren's Timetable, when does renal TB typically develop? | 5-25 years after primary infection.
17. What are the three major transitions in the natural history of TB? | Exposure
    Infection
    Disease.

CLINICAL PRESENTATIONS (PULMONARY TB)

18. What is the hallmark of Primary Pulmonary TB in children? | Large regional lymphadenitis compared with a small initial lung focus.
19. What is the usual radiologic sequence (3) in Primary Pulmonary TB? | Hilar lymphadenopathy
    Focal hyperinflation
    Atelectasis.
20. What is Progressive Primary Pulmonary Disease? | A complication where the primary focus enlarges, caseates, and liquefies.
21. In which pediatric age group can Reactivation TB occur? | Adolescence (often >7 years old).
22. What are the most common sites (3) for Reactivation TB? | Original parenchymal focus
    Lymph nodes
    Simon Foci (apical seedings).
23. What are the most common radiographic findings in Reactivation TB? | Extensive infiltrates and thick-walled cavities in the upper lobes.

DIAGNOSIS & WORK-UP

24. Presumptive TB in a child is suspected if they have 3 or more of what findings (6)? | Cough >2 weeks
    Fever >2 weeks
    Failure to respond to antibiotics
    Failure to regain health post-virus
    FTT
    Lethargy.
25. How is a TB "close contact" or "TB Exposure" defined? | Prolonged, frequent, or intense contact with an infectious TB patient.
26. What does the Tuberculin Skin Test (TST or PPD) detect? | A delayed (Type IV) cellular hypersensitivity to TB antigens.
27. What is the "window period" for the TST? | 2-12 weeks from exposure to a detectable reaction.
28. When is a TST result of ≥ 5mm considered positive in children? | Close contact, clinical findings of TB, suggestive CXR, or immunocompromised.
29. For which age group is sputum collection recommended for TB diagnosis? | Children more than 5 years old or who can expectorate.
30. How many sputum specimens should be sent for microscopy, and when? | Two specimens: one spot and one early morning, or two collected 1-2 hours apart.
31. What is the only contraindication to collecting sputum for DSSM? | Massive hemoptysis (200-600 ml in 24 hours).
32. In which children is gastric washing/aspiration used for sputum collection? | Children less than 5 years old or who cannot expectorate.
33. Why should KY jelly not be used as a lubricant for gastric washing? | It is bacteriostatic.
34. What is the sensitivity of AFB smears of gastric aspirates? | Low; positive in fewer than 10% of cases.
35. What is the positivity rate of sputum cultures from gastric aspirate specimens? | 30%-40% of cases.
36. What do Interferon Gamma Release Assays (IGRAs) indicate, and what can they NOT be used for? | They indicate TB infection (LTBI); NOT for diagnosing active TB.
37. What is the Xpert MTB/RIF assay? | An automated NAAT that detects TB bacteria and Rifampicin resistance in <2 hours.
38. How many bacilli are needed for a positive AFB smear versus a positive culture? | Smear: 5,000-10,000 bacilli/mL; Culture: 10-100 organisms.
39. What is the commonest chest radiologic finding in Primary TB? | Lymphadenopathy.
40. Why might radiographic findings worsen in the first 3 months of anti-TB treatment? | This can be a normal part of the treatment response and not a sign of failure.
41. What do the nodules of Miliary (Disseminated) TB on a chest x-ray resemble? | Millet seeds (small, uniformly sized nodules).

EXTRAPULMONARY TUBERCULOSIS (EPTB)

42. What percentage of pediatric TB cases does EPTB account for? | 30-40%.
43. What are the most common forms (3) of EPTB in children? | Lymphatic (adenitis)
    Pleural
    Bone TB.
44. What are the most fatal forms (3) of EPTB? | Pericardial
    Meningeal
    Miliary TB.
45. What are some clinical clues (5) for suspecting EPTB? | Monoarticular arthritis
    Sterile pyuria
    Pericardial effusion
    Vertebral osteomyelitis
    Chronic cervical lymphadenopathy.
46. What is the most common form of extrapulmonary TB in children? | Cervical lymphadenopathy (Scrofula).
47. What is Scrofuloderma? | A draining sinus tract formed when a tuberculous cervical lymph node ruptures through the skin.
48. In Cardiac TB, what is the main finding and its typical measurement on CT? | Pericardial involvement; often with pericardial thickening of >3mm.
49. What is the most common type of CNS TB and the most common cause of TB-related mortality? | TB Meningitis.
50. In a child with basilar meningitis, hydrocephalus, or cranial nerve palsies, what treatment should be considered? | Anti-TB treatment.
51. What is the most common complication of CNS TB? | Communicating hydrocephalus.
52. What are Tuberculomas? | Intracranial space-occupying lesions that are frequently multiple.
53. How do TB abscesses differ from tuberculomas? | Typically solitary, larger, and associated with a more accelerated clinical course.
54. Why is TB of the bones and joints common in young children? | Due to increased blood flow in growing bones.
55. TB arthritis is typically monoarticular, affecting which joints most commonly? | The hip and knee.
56. What is the "Phemister Triad" for TB arthritis on radiograph? | Juxta-articular osteoporosis
    Peripherally located osseous erosions
    Gradual narrowing of the joint space.
57. Which spinal region does TB of the Spine (Pott's disease) most commonly affect? | Lower thoracic and upper lumbar vertebrae.
58. What is a "gibbus" deformity a characteristic finding of? | Pott's disease.
59. What is the most common clinical manifestation of abdominal TB? | Peritonitis.
60. Which region is involved in 80-90% of gastrointestinal TB cases? | The ileocecal region.
61. What is the Fleischner sign in GI TB? | Thickening of ileocecal valve lips or a wide gaping valve with narrowing of the terminal ileum.
62. How is Disseminated TB defined? | Involvement of two or more organ systems.

TREATMENT OF TUBERCULOSIS

63. For whom is six months of Isoniazid Preventive Therapy (IPT) indicated? | Asymptomatic children <5 years old who are household contacts of a confirmed TB case.
64. What is the standard dose for INH in Isoniazid Preventive Therapy (IPT)? | 10 mg/kg.
65. What is the standard 6-month regimen for new, drug-susceptible TB? | 2 months of HRZE (intensive phase) followed by 4 months of HR (continuation phase).
66. For which types of TB is treatment extended to a total of 10-12 months? | TB meningitis or TB of the bones and joints.
67. What are the standard pediatric dosages for the four first-line anti-TB drugs? | Isoniazid (H): 10 mg/kg
    Rifampicin (R): 15 mg/kg
    Pyrazinamide (Z): 25-30 mg/kg
    Ethambutol (E): 20 mg/kg.
68. When is a patient with clinically diagnosed TB considered non-contagious? | After one week of uninterrupted treatment.
69. When is a patient with bacteriologically confirmed TB considered non-contagious? | After a negative follow-up sputum smear microscopy (DSSM).
70. Why is sputum smear microscopy (DSSM), not Xpert, used for treatment follow-up? | Xpert cannot differentiate between live and dead bacilli.
71. What is the relative hepatotoxicity of the first-line anti-TB drugs? | Pyrazinamide > INH > Rifampicin.
72. What side effect can Isoniazid cause, and how is it prevented? | Peripheral neuropathy; prevented by co-administering Pyridoxine (Vitamin B6).
73. What side effect can Ethambutol cause? | Optic neuritis (decreased visual acuity and color blindness).
74. How is Drug-Induced Liver Injury (DILI) defined? | AST >3x ULN with symptoms, or >5x ULN without symptoms.
75. If a patient on TB treatment develops jaundice, what is the immediate action? | All hepatotoxic drugs must be stopped.
76. After DILI resolves, in what order are TB drugs restarted? | Rifampicin first, then INH, then Pyrazinamide.
77. For which TB conditions (4) is adjunctive steroid therapy indicated? | TB meningitis
    TB pericarditis
    Endobronchial TB
    Severe miliary TB.

DRUG-RESISTANT TB

78. The Philippines has a high prevalence of resistance to which first-line TB drug? | Isoniazid (INH).
79. How is MDR-TB (Multi-Drug Resistant TB) defined? | TB resistant to at least INH and Rifampicin.
80. In the Philippines, how is a GeneXpert result of "Rifampicin-Resistant" interpreted? | The case is already considered MDR-TB.
81. How is XDR-TB (Extensively Drug-Resistant TB) defined? | MDR-TB with additional resistance to any fluoroquinolone AND any second-line injectable agent.
82. Who are considered suspects for MDR-TB (3 groups)? | Treatment failure patients
    Relapse cases
    Contacts of known MDR-TB patients.

SPECIAL SITUATIONS IN TB

83. The presentation of TB disease in a child is a significant indicator of what in the community? | Recent and ongoing transmission of M. tuberculosis.
84. What is the most common route of TB transmission to a newborn? | Postnatal airborne transmission from an adult with active pulmonary TB.
85. How should a newborn of a mother with LTBI be managed? | Not separated at birth and can be given BCG.
86. When should a newborn of a mother with active TB disease be isolated? | If the mother has been on anti-TB treatment for less than 2 weeks.

HIGH-YIELD COMPARISONS FOR EXAMS

87. How is TB Exposure defined? | Contact with a TB case, but has a negative TST, no symptoms, and a normal CXR.
88. How is TB Infection (LTBI) defined? | Has a positive TST (or IGRA), but has no symptoms and a normal CXR.
89. How is TB Disease defined? | Bacteria are actively multiplying; patient has symptoms and may have abnormal CXR/positive bacteriology.
90. What is the key radiographic finding of Primary TB in children? | Prominent hilar or mediastinal lymphadenopathy with a small lung focus.
91. What is the classic radiographic finding of Reactivation TB in adolescents? | Upper lobe/apical infiltrates with cavitation.
92. Can TST/IGRA distinguish between latent infection and active disease? | No, they only detect an immune response to M. tuberculosis.
93. What is Xpert MTB/RIF used to diagnose? | ACTIVE TB disease (by detecting bacterial DNA) and Rifampicin resistance.
94. When is Sputum Collection the preferred diagnostic method? | For patients who can voluntarily expectorate, typically children >5 years.
95. When is Gastric Washing used for diagnosis? | For infants and young children (<5 years) who cannot expectorate swallowed secretions.
96. What is Scrofula? | TB infection of the cervical lymph nodes, presenting as a firm, non-tender mass.
97. What is Scrofuloderma? | A complication where a caseous lymph node ruptures through the skin, creating a draining sinus.
98. What is a Tuberculoma in the CNS? | A solid or semi-solid caseous mass, frequently multiple, behaving like a tumor.
99. What is a TB Abscess in the CNS? | A liquid pus-filled cavity, typically solitary, larger, and with a more rapid clinical course.
100. How is MDR-TB (Multi-Drug Resistant) defined? | Resistant to at least Isoniazid (INH) and Rifampicin (RMP).
101. How is XDR-TB (Extensively Drug-Resistant) defined? | MDR-TB with additional resistance to any fluoroquinolone AND a second-line injectable.
102. What is the key difference in TB transmission dynamics between children and adults? | Children are paucibacillary and rarely transmit; Adults are often multibacillary and are the primary source.
103. What is Phemister's Triad used to describe? | Radiographic findings for tuberculous arthritis (joint infection).
104. What does Pott's Disease specifically refer to? | TB of the spine (vertebral infection), which can cause a "gibbus" deformity.
105. What are the most common forms of EPTB in children? | Lymphatic (scrofula), Pleural, and Bone/Joint TB.
106. What are the most fatal forms of EPTB? | Pericardial, Meningeal (TB Meningitis), and Miliary TB.

4.3

Summary

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NEISSERIA GONORRHOEAE (GONOCOCCUS)

General Characteristics & Transmission

• Neisseria gonorrhoeae is a nonmotile, aerobic, non-spore-forming, gram-negative intracellular diplococcus.
• Infection with N. gonorrhoeae only occurs in humans and is shed in the exudate and secretions of infected mucosal surfaces.
• Transmission of N. gonorrhoeae occurs through sexual contact or during parturition (childbirth).
• N. gonorrhoeae primarily infects columnar epithelium.

Clinical Manifestations

• In postpubertal males, N. gonorrhoeae infection manifests as urethritis and epididymitis.
• In postpubertal females, N. gonorrhoeae can cause Acute Pelvic Inflammatory Disease (PID), which comprises acute endometritis, salpingitis, and peritonitis.
• A key sign of gonorrhea is a purulent, pus-like, exudative, and foul-smelling discharge, which carries a risk of infertility.***
• Perihepatitis, also known as Fitz-Hugh-Curtis syndrome, can occur in females from the dissemination of N. gonorrhoeae from the fallopian tubes to the liver capsule.
• Asymptomatic gonorrhea is common, occurring in 80% of sexually mature females and 20% of males. Most pharyngeal GC infections are also asymptomatic.
• The primary infection in uncomplicated gonorrhea can present as urethritis, vulvovaginitis, cervicitis, or ophthalmitis, with a hallmark of PURULENT DISCHARGES.***
• Prepubertal females are predisposed to vulvovaginitis from N. gonorrhoeae due to their thin, noncornified vaginal epithelium and alkaline vaginal pH.
• In neonates and mature females, the cornification of the vaginal epithelium due to estrogen helps resist N. gonorrhoeae infection.
• During menses in postpubertal females, decreased bactericidal activity of cervical mucus facilitates the passage of gonococci into the upper reproductive tract, leading to salpingitis.

Disseminated Gonococcal Infection (DGI)

• Disseminated Gonococcal Infection (DGI) is the hematogenous spread of N. gonorrhoeae, occurring in 1-3% of cases.
• Populations at risk for DGI include women (especially menstruating, pregnant, or postpartum), asymptomatic carriers, neonates, homosexuals, and the immunocompromised.
• DGI presents as two clinical syndromes: Tenosynovitis-dermatitis syndrome and Suppurative arthritis syndrome.
• The Tenosynovitis-dermatitis syndrome of DGI features prominent systemic signs, polyarthralgia, positive blood cultures (30-40%), and negative synovial fluid cultures.
• The Suppurative arthritis syndrome of DGI features less prominent systemic signs, monoarticular arthritis, usually negative blood cultures, and positive synovial fluid cultures (45-55%).

Diagnosis

• A presumptive diagnosis of gonorrhea in males can be made by identifying gram-negative intracellular diplococci within leukocytes in a urethral discharge specimen.
• Specific diagnostic tests for gonorrhea include culture, nucleic acid hybridization tests, and Nucleic Acid Amplification Tests (NAAT).
• To differentiate from N. meningitidis, N. gonorrhoeae ferments glucose only, whereas N. meningitidis ferments both glucose and maltose.

Treatment and Prevention

• The drug of choice (DOC) for N. gonorrhoeae infection is Ceftriaxone.
• For uncomplicated gonorrhea, the treatment is Ceftriaxone 50mg/kg IM as a single dose.
• For gonococcal bacteremia or arthritis, the treatment is Ceftriaxone 50mg/kg/day for 7 days.
• For gonococcal meningitis, the treatment duration is 10-14 days for children and above, and 21 days for neonates.
• For neonatal gonococcal ophthalmia, the treatment is Ceftriaxone 50 mg/kg IM single dose, with frequent irrigation of the eyes with normal saline solution.
• According to lecturer notes, for females with gonorrhea, Doxycycline is often added to the treatment regimen.
• Alternative drugs for gonorrhea include Cefixime, Ceftizoxime, and Cefotaxime.
• Prevention of gonococcal ophthalmia neonatorum involves applying 1% silver nitrate drops, 0.5% Erythromycin ointment, or 1% Tetracycline ointment to the newborn's eyes.

TREPONEMA PALLIDUM (SYPHILIS)

General Characteristics & Transmission

• Treponema pallidum is a long, motile spirochete that causes syphilis, a chronic, systemic sexually transmitted infection.
• Acquired syphilis is transmitted almost exclusively by sexual contact, but also via transfusion of contaminated blood or direct contact with infected tissues.
• Congenital syphilis is transmitted from an infected mother to her fetus via transplacental transmission at any stage of pregnancy.
• The risk of congenital transmission is highest during the first 4 years of the mother's primary, secondary, and early latent syphilis.
• Risk factors for congenital syphilis include lack of prenatal care, cocaine abuse, and trading sex for drugs.

Clinical Manifestations of Acquired Syphilis

• Primary Syphilis is characterized by a painless chancre at the site of inoculation plus regional lymphadenitis, appearing after an incubation period of 10-90 days.
• Secondary Syphilis occurs 2-10 weeks after the chancre heals and is caused by spirochetemia, leading to various skin and systemic manifestations.
• Latent Syphilis is a seroreactive period with no clinical signs. It is defined as early latent if acquired within the preceding year and late latent if over one year's duration.
• Tertiary Syphilis occurs 15-30 years after the initial infection and is characterized by neurologic, cardiovascular, and gummatous lesions, which are specific to this stage.

Clinical Manifestations of Congenital Syphilis

• Infants with congenital syphilis are often asymptomatic at birth.
• Early signs of congenital syphilis (appearing before 2 years of age) include hepatosplenomegaly, jaundice, increased liver enzymes, and diffuse lymphadenopathy.
• Late signs of congenital syphilis include:
  • Hutchinson teeth: Peg-shaped, notched upper central incisors that erupt around the 6th year of life.
  • Saddle nose: Depression of the nasal root due to destruction of adjacent bone and cartilage.
  • Saber shins: Anterior bowing of the mid-portion of the tibia.
  • Rhagades: Linear scars around the mouth, anus, and genitalia.
  • Other late stigmata include Olympian brow, Clutton joints (painless knee swelling), interstitial keratitis, and 8th nerve deafness.

Diagnosis

• The definitive diagnosis of syphilis is made by demonstrating T. pallidum via darkfield microscopy or direct fluorescent antibody testing of specimens from lesions, placenta, or umbilical cord.
• Presumptive diagnosis uses serologic tests, which are divided into two types:
  • Nontreponemal tests (VDRL, RPR) are used for screening and monitoring therapy response, as their titers correlate with disease activity. They can produce false-positive results.
  • Treponemal tests (TPHA, FTA-ABS, TPPA) are used to confirm a diagnosis, as they measure specific antibodies to T. pallidum. They typically remain positive for life and their titers do not correlate with disease activity.
• For monitoring treatment response, a nontreponemal test like the RPR quantitative is used.
• In a neonate, an RPR titer that is fourfold higher than the maternal titer is considered a definitive sign of active congenital syphilis infection.

Treatment

• The drug of choice (DOC) for all forms of syphilis is Penicillin. Parenteral Penicillin G is the only documented effective treatment for congenital syphilis, neurosyphilis, and syphilis during pregnancy.
• The Jarisch-Herxheimer reaction is an acute systemic febrile reaction that can occur after starting penicillin treatment, caused by the release of antigens from dying spirochetes. It is NOT an indication to discontinue Penicillin.
• Alternative medications for syphilis mentioned in lecturer notes include Macrolides, Ceftriaxone, and Quinolones.

CHLAMYDIA TRACHOMATIS

General Characteristics & Manifestations

• Chlamydia trachomatis is a major cause of epididymitis and accounts for 23-55% of all cases of nongonococcal urethritis.
• Up to 75% of women with chlamydial infection are asymptomatic; it is also common for men to be asymptomatic.
• The characteristic discharge in Chlamydia infection is mucoid, in contrast to the purulent discharge of gonorrhea.
• Clinical manifestations of Chlamydia include acute urethral syndrome, epididymitis, cervicitis, salpingitis, proctitis, and Pelvic Inflammatory Disease (PID).
• Perinatally acquired rectal and vaginal Chlamydia infections can persist for 3 years or longer in a child.
• The detection of C. trachomatis in the vagina or rectum of a young child is NOT absolute evidence of sexual abuse.

Diagnosis and Complications

• The definitive diagnosis of Chlamydia is by isolation in tissue culture or microscopic identification of characteristic "INTRACYTOPLASMIC INCLUSIONS" using fluorescent antibody staining.
• Other diagnostic tests include Nucleic Acid Amplification Tests (NAATs), PCR, and GeneXpert.
• Complications of Chlamydia infection in women include Fitz-Hugh-Curtis syndrome, salpingitis, Pelvic Inflammatory Disease (PID), and secondary infertility or ectopic pregnancy.

Treatment

• For uncomplicated C. trachomatis genital infection in men and non-pregnant women, the recommended treatment is Azithromycin 1 gram PO as a single dose PLUS Doxycycline 100mg PO twice daily for 7 days.
• For uncomplicated Chlamydia infection in pregnant women, the treatment is Azithromycin 1 gram PO as a single dose OR Amoxicillin 500mg PO three times daily for 7 days.
• When treating empirically for STIs, it is common to prescribe a regimen that covers both Chlamydia and gonorrhea (e.g., Ceftriaxone plus Azithromycin).
• Sexual partners of a patient with nongonococcal urethritis from the preceding 60 days should be treated. The most recent sexual partner should always be treated, regardless of last contact.

PEDIATRIC HIV/AIDS

Transmission and Prevention

• Perinatal (Mother-To-Child-Transmission, MTCT) of HIV can occur antenatally, during delivery, or through breastfeeding.
• Risk factors for MTCT include high maternal viral load, low maternal CD4 count, vaginal delivery, prolonged rupture of membranes, and breastfeeding.
• To prevent MTCT, pregnant women should be screened for HIV every trimester.
• The four principles of HIV transmission are Exit, Sufficient viral load (in blood, breastmilk, semen, vaginal fluid), Survival, and Entry.

Management of HIV-Exposed Infants

• All HIV-exposed infants should receive post-exposure prophylaxis (PEP) starting within 6-12 hours of birth.
• Infants at low risk (mother on ART for ≥4 weeks) receive a single ARV (e.g., Nevirapine) for 6 weeks (replacement feeding) or 12 weeks (breastfeeding).
• Infants at high risk (mother untreated, late diagnosis, high viral load) receive a three-drug ARV regimen (e.g., Zidovudine + Lamivudine + Nevirapine) for 6-12 weeks.
• The WHO recommends breastfeeding for at least 12 months for infants of HIV-positive mothers on ART, but local guidelines (PIDSP) may recommend formula feeding to eliminate all risk.
• HIV-exposed infants should start Cotrimoxazole prophylaxis at 6 weeks of age, after ARV prophylaxis is completed and if HIV infection is not confirmed.

Diagnosis in Infants and Children

• For infants from birth to <18 months of age, HIV is diagnosed using a virologic test like RNA PCR or NAAT. The first test is done at 6 weeks of life.
• For children 18 months of age and older, HIV is diagnosed using an antibody test (e.g., rapid test kit), as maternal antibodies have waned by this age.
• To be declared HIV-negative, an exposed infant typically requires multiple negative tests, with a final negative antibody test at or after 18 months of age ("graduation").

Immunization

• HIV-exposed and infected children can receive most routine vaccines, including MMR and Varicella if they are not severely immunocompromised.
• Live vaccines that are CONTRAINDICATED for persons living with HIV (PLHIV) regardless of CD4 count are: BCG, Oral Polio (OPV), Herpes Zoster, Live attenuated influenza vaccine, and Live Typhoid (Ty21a). (Mnemonic: BO HIT).

Clinical Staging and Treatment (ARV)

• The WHO Clinical Staging system is used to classify the severity of HIV disease.
• Stage 3 HIV disease is marked by conditions like unexplained moderate malnutrition, persistent diarrhea, oral candidiasis, or pulmonary TB.
• Stage 4 HIV disease (AIDS) is defined by severe conditions such as Pneumocystis pneumonia, extrapulmonary TB, Kaposi sarcoma, or HIV encephalopathy.
• Antiretroviral therapy (ART) is recommended for all persons confirmed to be infected with HIV, regardless of their clinical or immunologic status.
• The first-line ARV regimen for infants and children <3 years old is typically two NRTIs (e.g., Abacavir + Lamivudine) plus one boosted protease inhibitor (Lopinavir/Ritonavir).
• The first-line ARV regimen for children 3 to <10 years old is typically two NRTIs (e.g., Abacavir + Lamivudine) plus one NNRTI (Efavirenz).
• Monitoring for ARV toxicity includes checking serum creatinine for Tenofovir (TDF), CBC for Zidovudine (AZT), and lipid profile for Efavirenz (EFV) and protease inhibitors.
• Treatment failure is defined as a plasma viral load above 1,000 copies/mL at any time beyond 6 months of starting effective ART.

High-Yield Comparisons

• Gonorrhea vs. Chlamydia Discharge: The discharge in Gonorrhea is typically purulent and thick, while the discharge in Chlamydia is more often mucoid or watery.
• Syphilis Chancre vs. Chancroid: The chancre of primary syphilis (T. pallidum) is typically single, firm, and painless. The chancroid of H. ducreyi is typically multiple, soft, and painful with associated tender lymphadenopathy.
• Syphilis Serology (Nontreponemal vs. Treponemal): Nontreponemal tests (RPR, VDRL) are for screening and monitoring treatment response. Treponemal tests (FTA-ABS, TPPA) are for confirming a diagnosis and remain positive for life.
• Disseminated Gonorrhea Syndromes: The Tenosynovitis-dermatitis syndrome presents with polyarthralgia and is often blood culture positive. The Suppurative Arthritis syndrome presents as a monoarticular septic arthritis and is often synovial fluid culture positive.
• HIV Testing in Infants vs. Older Children: Infants (<18 months) must be tested with a virologic test (PCR/NAT) to detect the virus itself. Older children (>18 months) can be tested with an antibody test.
• Infant HIV Prophylaxis (Low vs. High Risk): Low-risk infants (mother virally suppressed on ART) receive single-drug prophylaxis (Nevirapine). High-risk infants (mother untreated or with high viral load) receive triple-drug prophylaxis.
• Permitted vs. Contraindicated Vaccines in HIV: Most inactivated vaccines are permitted. Live vaccines like BCG, Oral Polio, and live influenza are contraindicated in persons living with HIV.
• Differentiating N. gonorrhoeae vs. N. meningitidis: N. gonorrhoeae ferments only glucose. N. meningitidis ferments both glucose and maltose.
• Congenital Syphilis (Early vs. Late): Early signs (<2 years) include hepatosplenomegaly and rhinitis ("snuffles"). Late signs (>2 years) are the permanent stigmata like Hutchinson teeth, saddle nose, and saber shins.
• Treatment of Empiric Urethritis/Cervicitis: A common approach is to treat for both Gonorrhea and Chlamydia simultaneously, using a regimen like single-dose IM Ceftriaxone plus oral Azithromycin. Doxycycline is often added for females.
• Jarisch-Herxheimer Reaction: This is an acute febrile reaction after starting antibiotic treatment for spirochetal infections like Syphilis. It is caused by toxin release from dying organisms and is NOT a drug allergy; treatment should be continued.
• WHO HIV Stage 3 vs. Stage 4: The presence of Tuberculosis (TB) places a patient in Stage 3. The presence of more severe opportunistic infections like Pneumocystis pneumonia (PCP) or CNS toxoplasmosis defines Stage 4 (AIDS).
• Monitoring ARV Side Effects: Remember to monitor CBC for Zidovudine (AZT) due to bone marrow suppression, renal function (creatinine) for Tenofovir (TDF), and lipids/glucose for protease inhibitors (e.g., Lopinavir/ritonavir).

QA

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NEISSERIA GONORRHOEAE (GONOCOCCUS)

1. What are the general characteristics of NEISSERIA GONORRHOEAE? | Gram-negative intracellular diplococcus.
   It is also nonmotile, aerobic, and non-spore-forming.
2. Where does infection with N. gonorrhoeae only occur and how is it shed? | Only in humans; shed in exudate and secretions of infected mucosal surfaces.
3. How is N. gonorrhoeae transmitted? (2) | 1. Sexual contact
   2. Parturition (childbirth).
4. What type of epithelium does N. gonorrhoeae primarily infect? | Columnar epithelium.
5. In postpubertal males, how does N. gonorrhoeae infection manifest? (2) | 1. Urethritis
   2. Epididymitis.
6. In postpubertal females, what can N. gonorrhoeae cause, comprising what conditions? (3) | Acute Pelvic Inflammatory Disease (PID).
   Comprised of: endometritis, salpingitis, and peritonitis.
7. What is a key sign of gonorrhea that carries a risk of infertility? | Purulent, foul-smelling discharge.
8. What syndrome can occur in females from the dissemination of N. gonorrhoeae from the fallopian tubes to the liver capsule? | Fitz-Hugh-Curtis syndrome (perihepatitis).
9. How common is asymptomatic gonorrhea in sexually mature females and males? | 80% of females and 20% of males.
10. What is the hallmark of the primary infection in uncomplicated gonorrhea? | Purulent discharges.
11. Why are prepubertal females predisposed to gonococcal vulvovaginitis? (2) | 1. Thin, noncornified vaginal epithelium
    2. Alkaline vaginal pH.
12. In neonates and mature females, what helps resist N. gonorrhoeae infection in the vagina? | Cornification of the vaginal epithelium due to estrogen.
13. During menses, what facilitates the passage of gonococci into the upper reproductive tract, leading to salpingitis? | Decreased bactericidal activity of cervical mucus.
14. What is Disseminated Gonococcal Infection (DGI)? | The hematogenous spread of N. gonorrhoeae.
15. What are the populations at risk for Disseminated Gonococcal Infection (DGI)? (5) | 1. Women (menstruating, pregnant, postpartum)
    2. Asymptomatic carriers
    3. Neonates
    4. Homosexuals
    5. The immunocompromised.
16. What are the two clinical syndromes of Disseminated Gonococcal Infection (DGI)? | 1. Tenosynovitis-dermatitis syndrome
    2. Suppurative arthritis syndrome.
17. What are the key features of the Tenosynovitis-dermatitis syndrome of DGI? | Polyarthralgia, positive blood cultures.
18. What are the key features of the Suppurative arthritis syndrome of DGI? | Monoarticular arthritis, positive synovial fluid cultures.
19. How is a presumptive diagnosis of gonorrhea made in males from a urethral discharge specimen? | Identifying gram-negative intracellular diplococci within leukocytes.
20. What are the specific diagnostic tests for gonorrhea? (3) | 1. Culture
    2. Nucleic acid hybridization tests
    3. Nucleic Acid Amplification Tests (NAAT).
21. How can N. gonorrhoeae be differentiated from N. meningitidis based on sugar fermentation? | N. gonorrhoeae ferments glucose only.
22. What is the drug of choice for N. gonorrhoeae infection? | Ceftriaxone.
23. What is the treatment for uncomplicated gonorrhea? | Ceftriaxone 50mg/kg IM as a single dose.
24. What is the treatment for gonococcal bacteremia or arthritis? | Ceftriaxone 50mg/kg/day for 7 days.
25. What is the treatment duration for gonococcal meningitis in children versus neonates? | 10-14 days for children; 21 days for neonates.
26. What is the treatment for neonatal gonococcal ophthalmia? | Ceftriaxone 50 mg/kg IM single dose, with frequent eye irrigation.
27. For females with gonorrhea, what drug is often added to the treatment regimen? | Doxycycline.
28. What are alternative drugs for gonorrhea? (3) | 1. Cefixime
    2. Ceftizoxime
    3. Cefotaxime.
29. How is gonococcal ophthalmia neonatorum prevented? (3) | 1. 1% silver nitrate drops
    2. 0.5% Erythromycin ointment
    3. 1% Tetracycline ointment.

TREPONEMA PALLIDUM (SYPHILIS)

30. What type of organism is Treponema pallidum and what disease does it cause? | A long, motile spirochete; causes syphilis.
31. How is acquired syphilis transmitted? (3) | 1. Sexual contact
    2. Transfusion of contaminated blood
    3. Direct contact with infected tissues.
32. How is congenital syphilis transmitted from an infected mother to her fetus? | Via transplacental transmission.
33. During which stages of the mother's infection is the risk of congenital syphilis transmission highest? | Primary, secondary, and early latent syphilis.
34. What are the risk factors for congenital syphilis? (3) | 1. Lack of prenatal care
    2. Cocaine abuse
    3. Trading sex for drugs.
35. What characterizes Primary Syphilis? (2) | 1. Painless chancre
    2. Regional lymphadenitis.
36. What is the cause of Secondary Syphilis, which occurs 2-10 weeks after the chancre heals? | Spirochetemia.
37. What is Latent Syphilis, and how are its sub-stages defined? | A seroreactive period with no clinical signs; early latent (<1 year), late latent (>1 year).
38. What are the characteristic lesions of Tertiary Syphilis? (3) | 1. Neurologic
    2. Cardiovascular
    3. Gummatous lesions.
39. How do infants with congenital syphilis often present at birth? | Asymptomatic.
40. What are early signs of congenital syphilis (appearing before 2 years of age)? (4) | 1. Hepatosplenomegaly
    2. Jaundice
    3. Increased liver enzymes
    4. Diffuse lymphadenopathy.
41. What are Hutchinson teeth, a late sign of congenital syphilis? | Peg-shaped, notched upper central incisors.
42. What is a "saddle nose" deformity in congenital syphilis? | Depression of the nasal root due to bone and cartilage destruction.
43. What are "saber shins," a late sign of congenital syphilis? | Anterior bowing of the mid-portion of the tibia.
44. What are "rhagades" in congenital syphilis? | Linear scars around the mouth, anus, and genitalia.
45. What are other late stigmata of congenital syphilis? (4) | 1. Olympian brow
    2. Clutton joints
    3. Interstitial keratitis
    4. 8th nerve deafness.
46. How is a definitive diagnosis of syphilis made? (2) | 1. Darkfield microscopy
    2. Direct fluorescent antibody testing.
47. What are the two types of serologic tests used for a presumptive diagnosis of syphilis? | Nontreponemal and Treponemal tests.
48. What are nontreponemal tests (VDRL, RPR) used for in syphilis diagnosis, and what is a limitation? | Screening and monitoring therapy; can produce false-positive results.
49. What are treponemal tests (TPHA, FTA-ABS, TPPA) used for in syphilis diagnosis, and how long do they remain positive? | Confirming a diagnosis; typically remain positive for life.
50. For monitoring syphilis treatment response, which type of test is used? | A nontreponemal test like the RPR quantitative.
51. What RPR titer in a neonate is considered a definitive sign of active congenital syphilis infection? | A titer that is fourfold higher than the maternal titer.
52. What is the drug of choice for all forms of syphilis? | Penicillin.
53. What is the Jarisch-Herxheimer reaction and should Penicillin be discontinued if it occurs? | An acute systemic febrile reaction; No, it is not an indication to discontinue.
54. What are alternative medications for syphilis mentioned in lecturer notes? (3) | 1. Macrolides
    2. Ceftriaxone
    3. Quinolones.

CHLAMYDIA TRACHOMATIS

55. Chlamydia trachomatis is a major cause of what two conditions? | 1. Epididymitis
    2. Nongonococcal urethritis.
56. What percentage of women with chlamydial infection are asymptomatic? | Up to 75%.
57. What is the characteristic discharge in Chlamydia infection, in contrast to gonorrhea? | Mucoid.
58. What are the clinical manifestations of Chlamydia infection? (6) | 1. Acute urethral syndrome
    2. Epididymitis
    3. Cervicitis
    4. Salpingitis
    5. Proctitis
    6. Pelvic Inflammatory Disease (PID).
59. How long can perinatally acquired rectal and vaginal Chlamydia infections persist in a child? | 3 years or longer.
60. Is the detection of C. trachomatis in a young child's vagina or rectum absolute evidence of sexual abuse? | No.
61. What characteristic microscopic finding is used for the definitive diagnosis of Chlamydia? | Intracytoplasmic inclusions.
62. What are other diagnostic tests for Chlamydia? (3) | 1. Nucleic Acid Amplification Tests (NAATs)
    2. PCR
    3. GeneXpert.
63. What are the complications of Chlamydia infection in women? (4) | 1. Fitz-Hugh-Curtis syndrome
    2. Salpingitis
    3. PID
    4. Secondary infertility or ectopic pregnancy.
64. What is the recommended treatment for uncomplicated C. trachomatis in men and non-pregnant women? | Azithromycin 1g PO single dose PLUS Doxycycline 100mg PO twice daily for 7 days.
65. What is the treatment for uncomplicated Chlamydia infection in pregnant women? (2 options) | 1. Azithromycin 1g PO single dose OR
    2. Amoxicillin 500mg PO three times daily for 7 days.
66. When treating empirically for STIs, what is a common regimen to cover both Chlamydia and gonorrhea? | Ceftriaxone plus Azithromycin.
67. Who should be treated if a patient has nongonococcal urethritis from Chlamydia? | Partners from the preceding 60 days, and always the most recent partner.

PEDIATRIC HIV/AIDS

68. When can perinatal (Mother-To-Child-Transmission) of HIV occur? (3) | 1. Antenatally
    2. During delivery
    3. Through breastfeeding.
69. What are the risk factors for Mother-To-Child-Transmission of HIV? (5) | 1. High maternal viral load
    2. Low maternal CD4 count
    3. Vaginal delivery
    4. Prolonged rupture of membranes
    5. Breastfeeding.
70. To prevent Mother-To-Child-Transmission, how often should pregnant women be screened for HIV? | Every trimester.
71. What are the four principles of HIV transmission? | 1. Exit
    2. Sufficient viral load
    3. Survival
    4. Entry.
72. When should all HIV-exposed infants receive post-exposure prophylaxis (PEP)? | Starting within 6-12 hours of birth.
73. What PEP do low-risk HIV-exposed infants receive? | A single ARV (e.g., Nevirapine).
74. What PEP do high-risk HIV-exposed infants receive? | A three-drug ARV regimen.
75. What is the WHO recommendation for feeding infants of HIV-positive mothers on ART? | Breastfeeding for at least 12 months.
76. When should HIV-exposed infants start Cotrimoxazole prophylaxis? | At 6 weeks of age (after ARV prophylaxis).
77. For infants <18 months, how is HIV diagnosed and when is the first test done? | Using a virologic test (RNA PCR or NAAT); first test at 6 weeks of life.
78. For children ≥18 months of age, how is HIV diagnosed? | Using an antibody test.
79. How is an HIV-exposed infant declared HIV-negative ("graduated")? | A final negative antibody test at or after 18 months of age.
80. Can HIV-infected children receive live vaccines like MMR and Varicella? | Yes, if they are not severely immunocompromised.
81. Which live vaccines are contraindicated for persons living with HIV (PLHIV)? (Mnemonic: BO HIT) | BCG, Oral Polio (OPV), Herpes Zoster, Live attenuated influenza, Live Typhoid (Ty21a).
82. What system is used to classify the severity of HIV disease? | The WHO Clinical Staging system.
83. What are some conditions that mark WHO Clinical Stage 3 HIV disease? | Unexplained moderate malnutrition, persistent diarrhea, oral candidiasis, or pulmonary TB.
84. What are some conditions that define WHO Clinical Stage 4 HIV disease (AIDS)? | Pneumocystis pneumonia, extrapulmonary TB, Kaposi sarcoma, or HIV encephalopathy.
85. Who should receive antiretroviral therapy (ART) for HIV infection? | All persons confirmed to be infected with HIV.
86. What is the first-line ARV regimen for infants and children <3 years old with HIV? | Two NRTIs plus one boosted protease inhibitor.
87. What is the first-line ARV regimen for children 3 to <10 years old with HIV? | Two NRTIs plus one NNRTI.
88. What labs should be monitored for toxicity with Tenofovir (TDF), Zidovudine (AZT), and protease inhibitors? | Creatinine (TDF), CBC (AZT), and lipid profile (protease inhibitors).
89. How is HIV treatment failure defined after 6 months of effective ART? | Plasma viral load above 1,000 copies/mL.

High-Yield Comparisons

90. Compare the discharge in Gonorrhea vs. Chlamydia. | Gonorrhea: purulent and thick.
    Chlamydia: mucoid or watery.
91. Compare the chancre of primary syphilis vs. a chancroid. | Syphilis: single, firm, painless.
    Chancroid: multiple, soft, painful.
92. Compare nontreponemal vs. treponemal serology for syphilis. | Nontreponemal (RPR, VDRL): Screening & monitoring.
    Treponemal (FTA-ABS): Confirming diagnosis.
93. Compare the two syndromes of Disseminated Gonorrhea. | Tenosynovitis-dermatitis: Polyarthralgia, blood culture positive.
    Suppurative Arthritis: Monoarticular, synovial fluid culture positive.
94. Compare HIV testing in infants (<18 months) vs. older children (>18 months). | Infants: Virologic test (PCR/NAT).
    Older children: Antibody test.
95. Compare infant HIV prophylaxis for low-risk vs. high-risk exposure. | Low-risk: Single-drug prophylaxis (Nevirapine).
    High-risk: Triple-drug prophylaxis.
96. Compare permitted vs. contraindicated vaccines in HIV. | Permitted: Most inactivated vaccines.
    Contraindicated: Live vaccines (BCG, Oral Polio).
97. Differentiate N. gonorrhoeae vs. N. meningitidis by sugar fermentation. | N. gonorrhoeae: ferments only glucose.
    N. meningitidis: ferments glucose and maltose.
98. Compare early vs. late signs of congenital syphilis. | Early (<2yr): Hepatosplenomegaly, rhinitis.
    Late (>2yr): Hutchinson teeth, saddle nose, saber shins.
99. What is the common approach for empiric treatment of urethritis/cervicitis? | Treat for both Gonorrhea and Chlamydia simultaneously (e.g., Ceftriaxone + Azithromycin).
100. What is the Jarisch-Herxheimer Reaction? | An acute febrile reaction after starting antibiotics for spirochetes like Syphilis; not a drug allergy.
101. Compare WHO HIV Stage 3 vs. Stage 4 defining illnesses. | Stage 3: Tuberculosis (TB).
     Stage 4: Pneumocystis pneumonia (PCP) or other severe opportunistic infections.
102. Besides Zidovudine (AZT), what ARV side effects should be monitored? | Renal function (creatinine) for Tenofovir (TDF), and lipids/glucose for protease inhibitors.

4.4

Summary

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FUNGAL INFECTIONS

CANDIDA

• Candida - General: Candida are members of the normal flora of humans and colonize mucosal surfaces soon after birth, posing a risk of endogenous infection.
• Candida - Species: While the Candida genus has over 314 species, fewer than 20 cause candidiasis.
• Candida - Prevalence: Candidiasis is the most prevalent systemic mycosis.
• Candida - Common Agents: The five most common causative agents of candidiasis are C. albicans, C. parapsilosis, C. glabrata, C. tropicalis, and C. krusei.

Candida albicans

• C. albicans - Pathogenesis: C. albicans exists as a commensal but can convert to a pathogen depending on the host's immune or endocrine status.
• C. albicans - Morphology: C. albicans is polymorphic, growing as budding yeast cells, pseudohyphae, and true hyphae. It is Gram-positive and 10-12 μm in diameter.
• C. albicans - Genetic Control: The transcription repressor NRg1 is needed for C. albicans to maintain its yeast form.
• C. albicans - Identification: Production of germ tubes and terminal chlamydospores are key characteristics used to identify C. albicans in the laboratory.
• Germ Tube Test - Principle: The germ tube test is a rapid presumptive identification for C. albicans, as germ tube formation is associated with increased protein and RNA synthesis.
• Germ Tube Test - Positive Result: A positive test shows a short hyphal extension arising from a yeast cell with no constriction at the point of origin. Examples include Candida albicans and Candida dubliniensis.
• Germ Tube Test - Negative Result: A negative test shows no hyphal extension or an extension that is constricted at the origin. Examples include C. tropicalis and C. glabrata.

Candidiasis

• Candidiasis - Risk Factors (Non-Neutropenic): Risk factors for invasive candidiasis in non-neutropenic patients include anatomical disruption (surgery, wounds, burns), ICU stays, intravascular catheters, TPN, and antibiotic use (especially for >7 days).
• Candidiasis - Risk Factors (Neutropenic): Risk factors for invasive candidiasis in neutropenic cancer patients include mucosal ulceration, intravascular catheters, and cytotoxic/immunosuppressive drugs.
• Candidiasis - Community Risk Factors: Community risk factors for invasive candidiasis include hemodialysis and diabetes.
• Invasive Candidiasis - Clinical Forms: Other clinical forms of invasive candidiasis include Bone & Joint, Chronic Hepatosplenic, Endocarditis, Endophthalmitis, Renal, Skin lesions, CNS infection, Peritonitis, and UTI.
• Chronic Mucocutaneous Candidiasis: This is a rare form of candidiasis caused by a genetic defect in T-cell responsiveness to Candida.

Candida Diagnosis & Treatment

• Candida - Diagnosis: Diagnosis of Candida relies on morphology on Gram stain, culture on Sabouraud dextrose agar, and biochemical tests (like API) for speciation.
• Candida Speciation - Importance: Speciation of Candida is important due to significant antifungal resistance among different species.
• Oral Candidiasis - Treatment (Adults): Mild oral candidiasis in adults is treated with clotrimazole troches or miconazole buccal tablets; moderate to severe forms require oral Fluconazole.
• Oral Candidiasis - Treatment (Infants): Oral thrush in infants is treated with oral miconazole or Nystatin solution. Immunocompromised children may require oral fluconazole.
• Esophageal Candidiasis - Treatment: Esophageal candidiasis is treated with oral fluconazole. Refractory cases may require Itraconazole or Voriconazole.
• Candidemia/Invasive Candidiasis - Treatment Principle: A crucial step in treating candidemia is to remove the central venous catheter, as drug therapy alone is not sufficient.
• Candidemia - Treatment (Non-Neutropenic): The drug of choice for candidemia in non-neutropenic patients is an echinocandin (e.g., micafungin, caspofungin). Fluconazole is an alternative.
• Candidemia - Treatment (Neutropenic): The drug of choice for candidemia in neutropenic patients is an echinocandin. Alternatives include Amphotericin B (lipid formulation preferred).
• Emerging Candida - C. auris: Candida auris is an emerging pathogen that is often multidrug-resistant (especially to fluconazole and amphotericin B) and has caused healthcare-associated outbreaks.
• Emerging Candida - C. krusei: Candida krusei (now Pichia kudriavzevii) is of concern due to its relative intrinsic resistance to azoles and other antifungal drugs.

CRYPTOCOCCOSIS

• Cryptococcosis - General: Cryptococcosis is a subacute or chronic infection, most often involving the CNS, and is considered an AIDS-defining illness.
• Cryptococcus Varieties - Comparison:
  • C. neoformans: Has a worldwide distribution, is found in pigeon feces, and primarily infects immunocompromised hosts (AIDS). It is the most common cause of cryptococcosis.
  • C. gattii: Found in tropical/subtropical regions, associated with Eucalyptus trees, can infect normal hosts, and is associated with cryptococcomas and higher mortality.
• Cryptococcus - Pathogenesis: Infection occurs via inhalation of particles. A primary pulmonary infection may be asymptomatic but can disseminate, with the CNS being the most common site of dissemination.
• Cryptococcosis - Most Common Infection Site: The most common initial site of infection in cryptococcosis is the lungs (pulmonary infection).
• Cryptococcosis - Laboratory Diagnosis: The hallmark of diagnosis is the India Ink mount of CSF, which reveals the encapsulated yeast as a halo.
• Cryptococcosis - Culture: When grown on Niger seed agar or with caffeic acid, C. neoformans and C. gattii produce a characteristic brown colony effect.
• Cryptococcosis - Histopathology: The Mucicarmine stain is used in histopathology to stain the capsule of Cryptococcus red.
• Severe Cryptococcosis - Treatment Phases: Treatment for severe cryptococcosis is triphasic:
  1. Induction: Amphotericin B + flucytosine for ~2 weeks.
  2. Consolidation: High-dose fluconazole for ~8 weeks.
  3. Maintenance: Lower-dose fluconazole for ≥6-12 months.

SUPERFICIAL & CUTANEOUS MYCOSES

• Superficial Mycoses - Definition: These fungal diseases affect the outermost layer of the skin (stratum corneum) or hair shafts.
• Superficial Mycoses - Types:
  1. Pityriasis (Tinea) Versicolor: Caused by Malassezia species, resulting in hypo- or hyper-pigmented skin patches.
  2. White Piedra: Soft, beige nodules on hair shafts caused by Trichosporon species.
  3. Black Piedra: Firm, black nodules on the hair shaft caused by Piedraia hortae.
  4. Tinea Nigra: Brown to black stain on the palm or sole caused by Hortaea werneckii.
• Cutaneous Mycoses (Dermatophytes): These fungi are confined to the non-living outer layers of skin, hair, and nails, and produce keratinases.
• Dermatophyte Diagnosis - KOH Prep: A skin scraping with KOH preparation is the fastest and simplest diagnostic test for dermatophytes.
• Dermatophyte Genera - Infection Sites:
  • Trichophyton: Infects skin, hair, and nails ("Tri" for all three).
  • Microsporum: Infects hair and skin (not nails).
  • Epidermophyton: Infects skin and nails (not hair).
• Trichophyton rubrum: The most common cause of tinea corporis. Microscopically shows pyriform microconidia arranged like “birds on a wire.”
• Trichophyton tonsurans: A major cause of tinea capitis. Microscopically shows varied microconidia, including “match stick” shapes and balloon forms.
• Microsporum canis: A common cause of tinea capitis where infected hairs fluoresce bright green under a Wood's light. Microscopically characterized by large, spindle-shaped, thick-walled, spiny macroconidia.
• Epidermophyton floccosum: Characterized by the absence of microconidia and the presence of multiple smooth, club-shaped macroconidia, often in clusters.
• Tinea Capitis - Favus: A severe form of tinea capitis characterized by a scutulum (yellow, cup-shaped crust) and often caused by T. schoenleinii.
• Tinea Cruris (Jock Itch): An infection of the groin area where the scrotum and penis are typically spared.
• Tinea Unguium (Onychomycosis): A dermatophyte infection of the nail, frequently caused by T. rubrum, that is often resistant to topical antifungal agents.
• Tinea Pedis - Moccasin Type: Presents as chronic plantar erythema and hyperkeratosis in a moccasin-like distribution, often associated with the “two feet, one hand” presentation.
• Malassezia - Microscopy: In skin scrapings, Malassezia species classically show clusters of thick-walled blastospores and hyphae, known as the “spaghetti-and-meatballs appearance.”
• Malassezia - Associated Conditions:
  • Tinea Versicolor: M. globosa, M. sympodialis, M. restricta, M. furfur.
  • Neonatal Acne: M. sympodialis, M. globosa.
  • Seborrheic Dermatitis: M. globosa, M. restricta.
• Onychomycosis - Treatment: Oral therapy (e.g., Terbinafine) is more effective than topical therapy due to the nail plate barrier. LASER therapy offers "temporary cosmetic improvement" but is not a fungicidal therapy.

FILAMENTOUS FUNGI

• Aspergillosis - Common Pathogens: Aspergillus fumigatus and Aspergillus flavus are the most common causes of invasive disease. A. fumigatus accounts for over 90% of all Aspergillus infections.
• Aspergillosis - Pathogenesis & Forms:
  1. Aspergilloma: A "fungus ball" that colonizes a pre-existing lung cavity.
  2. Invasive Aspergillosis: Occurs in immunocompromised hosts.
  3. Allergic Aspergillosis: An allergic reaction to the fungus.
  4. Aflatoxicosis: Poisoning from ingestion of aflatoxin produced by A. flavus on contaminated food like peanuts.
• Aspergillus fumigatus - Microscopy: Shows uniseriate conidial heads with phialides covering only the upper two-thirds of the vesicle.
• Aspergillus flavus - Microscopy: Shows biseriate conidial heads and coarsely roughened conidiophores.
• Aspergillus niger - Microscopy: Shows biseriate conidial heads that are large, globose, and radiate, producing black conidia.
• Invasive Aspergillosis - Treatment: The drug of choice is Amphotericin B (often given IV in-patient). Itraconazole is an oral option.
• Mucormycosis - Risk Factors: Occurs in patients with diabetic ketoacidosis, hematologic malignancy, severe burns, or trauma. It has also been noted as a complication in severe COVID-19.
• Mucormycosis - Pathogenesis: Characterized by acute inflammation and angioinvasion (fungal invasion of blood vessels), which can lead to rapid progression and tissue necrosis.
• Mucormycosis - Agents: Caused by fungi in the order Mucorales, such as Rhizopus, Lichtheimia (formerly Absidia), and Rhizomucor.

PARASITIC INFECTIONS

INTESTINAL NEMATODES

• Nematode Classification - Habitat: Intestinal nematodes can inhabit the small intestine (e.g., Ascaris, Hookworm, Strongyloides) or the cecum/colon (e.g., Trichuris, Enterobius).
• Nematode Classification - Phasmids:
  • Aphasmids (No phasmids): Trichinella spiralis, Trichuris trichiura, Capillaria philippinensis.
  • Phasmids (Have phasmids): Strongyloides, Enterobius, Ascaris, Hookworms.
• Trichinella spiralis - Transmission & Disease: Causes trichinosis from eating raw or insufficiently cooked pork. Humans serve as both definitive and intermediate hosts.
• Trichinella spiralis - Diagnosis: The definitive diagnostic test is a muscle biopsy to find encysted larvae.
• Trichuris trichiura (Whipworm) - Egg Morphology: Eggs are characteristically barrel-shaped with polar plugs on each end.
• Trichuris trichiura - Clinical Manifestation: Heavy infections (>200 worms) can cause dysentery and rectal prolapse, especially in children.
• Capillaria philippinensis - Epidemiology: Endemic in the Philippines, first recorded in Northern Luzon, and associated with eating raw freshwater fish.
• Capillaria philippinensis - Disease: Causes intestinal capillariasis, leading to malabsorption and a protein-losing enteropathy, which can be fatal.
• Capillaria philippinensis - Egg Morphology: Eggs are peanut-shaped with flattened bipolar plugs, resembling Trichuris eggs but broader.
• Ascaris lumbricoides (Roundworm) - Life Cycle: Involves ingestion of embryonated eggs and a larval migration phase through the lungs, which can cause pneumonitis.
• Hookworm - Transmission: Infection occurs when filariform larvae in soil penetrate intact skin, often on the feet ("ground itch").
• Hookworm vs. Strongyloides Larva: In the rhabditiform stage, the hookworm larva has a long buccal cavity, whereas the Strongyloides larva has a short buccal cavity.
• Hookworm Species - Differentiation:
  • Ancylostoma duodenale (Old World): Has two pairs of ventral teeth in its buccal capsule. Its dorsal ray is tripartite.
  • Necator americanus (New World): Has a pair of semilunar cutting plates instead of teeth. Its dorsal ray is bipartite. It is the predominant human hookworm in the Philippines.
• Hookworm - Clinical Manifestation: Chronic infection leads to iron deficiency anemia due to the worms feeding on blood from the intestinal mucosa.
• Strongyloides stercoralis (Threadworm) - Unique Feature: Capable of autoinfection, allowing the infection to persist for decades, and can lead to hyperinfection syndrome in immunocompromised individuals.
• Strongyloides stercoralis - Clinical Manifestation: Dermatologic manifestation includes larva currens, a characteristic serpiginous urticarial rash.
• Strongyloides stercoralis - Diagnosis: Diagnosis is made by identifying larvae (rhabditiform) in the stool, not eggs. Stool examination is insensitive.
• Enterobius vermicularis (Pinworm) - Hallmark Symptom: The most common and characteristic symptom is intense perianal pruritus (pruritus ani), which is typically worse at night.
• Enterobius vermicularis - Diagnosis: Diagnosis is made using the perianal cellulose tape swab (Scotch tape test) to collect eggs from the perianal skin.
• Enterobius vermicularis - Egg Morphology: Eggs are characteristically asymmetrical, being flattened on one side (D-shaped or lopsided).

TISSUE NEMATODES (FILARIA)

• Lymphatic Filariasis (LF) - Causative Agents: Caused by Wuchereria bancrofti and Brugia malayi.
• Lymphatic Filariasis (LF) - Transmission: Transmitted by mosquito vectors (Aedes, Anopheles, Culex, Mansonia).
• Lymphatic Filariasis (LF) - Pathology: The most severe inflammation and lymphatic damage is elicited by dead or dying adult worms, leading to obstruction.
• Lymphatic Filariasis (LF) - Chronic Manifestations: Chronic disease can lead to lymphedema, elephantiasis (most commonly in lower extremities), and hydrocele.
• Hydrocele in LF: Hydrocele (fluid-filled sac around the testes) is the most common chronic manifestation of bancroftian filariasis (W. bancrofti).
• Lymphatic Filariasis (LF) - Diagnosis: The gold standard for diagnosis is the detection of circulating filarial antigen (CFA) using a rapid immunochromatographic test (ICT), which can be done anytime.
• Microfilariae - Blood Collection: For microscopic diagnosis of W. bancrofti (nocturnal periodicity), blood should be collected between 8 PM and 4 AM.
• Microfilariae - Differentiation (W. bancrofti vs. B. malayi):
  • W. bancrofti: Nuclei do not extend to the tail tip; sheath is unstained with Giemsa.
  • B. malayi: Nuclei do extend to the tail tip (has terminal/subterminal nuclei); sheath stains pink with Giemsa.
• Lymphatic Filariasis - Management: Management of elephantiasis is supportive, focusing on meticulous hygiene (washing affected parts), elevation, and exercise to prevent secondary bacterial infections.
• Toxocara Infection (Toxocariasis): A zoonosis from dog (T. canis) or cat (T. cati) roundworms. Humans are infected by ingesting eggs.
• Toxocariasis - Forms: Can manifest as visceral larva migrans (larvae migrate to organs like the liver) or ocular larva migrans (larvae migrate to the eye, causing vision loss).

CESTODES (TAPEWORMS)

• Taenia solium (Pork Tapeworm) - Hosts: Humans are the only definitive host (harboring the adult worm) but can also become an intermediate host by ingesting eggs, leading to cysticercosis.
• Cysticercosis: The infection with the larval stage (Cysticercus cellulosae) of T. solium. Neurocysticercosis (cysts in the brain) is the most serious form, often presenting with seizures.
• Taenia saginata (Beef Tapeworm) - Hosts: Humans are the only definitive host; cattle are the intermediate host. Humans cannot get cysticercosis from T. saginata.
• Taenia Egg Identification: The eggs of T. solium and T. saginata are morphologically indistinguishable.
• Taenia Species Differentiation (Scolex & Uterus):
  • T. solium: Scolex has 4 suckers and a rostellum with two rows of hooklets. Gravid proglottid has <13 primary lateral uterine branches.
  • T. saginata: Scolex has 4 suckers but no rostellum or hooklets (is "unarmed"). Gravid proglottid has >13 primary lateral uterine branches.
• Echinococcus granulosus (Dog Tapeworm): The smallest tapeworm of medical importance. Causes hydatid disease.
• Hydatid Disease: Humans are accidental intermediate hosts. Infection results in the formation of a hydatid cyst (larval stage), most commonly in the liver (70%) or lungs (20%), which contains "hydatid sand."

PROTOZOA

• Entamoeba histolytica - Disease: The only invasive amoeba, causing amebic colitis and potentially amebic liver abscess.
• Entamoeba histolytica - Transmission & Life Cycle: Infection is acquired by ingesting cysts (infective stage) in contaminated food/water. Cysts develop into trophozoites (invasive stage) in the colon.
• Entamoeba histolytica - Diagnosis: Finding trophozoites (may contain ingested RBCs) or cysts in the stool. Stool may have a scanty, fishy odor.
• Amebiasis - Treatment:
  • Symptomatic disease (colitis/abscess): Treat with a tissue agent like Metronidazole.
  • Asymptomatic cyst passer: Treat with a luminal agent like Diloxanide furoate.
• Leishmaniasis - Vector and Transmission: Transmitted by the bite of an infected female Phlebotomus sandfly, which injects the promastigote stage.
• Leishmaniasis - Human Stage: Inside human macrophages, promastigotes transform into amastigotes, the intracellular diagnostic stage.
• Leishmaniasis - Clinical Forms:
  1. Cutaneous: Most common form, causes skin sores ("oriental sores").
  2. Mucocutaneous: Parasite spreads to mucous membranes of the nose, mouth, throat.
  3. Visceral (Kala-azar): Affects internal organs (spleen, liver, bone marrow) and is life-threatening if untreated.
• African Trypanosomiasis (Sleeping Sickness) - Agent & Vector: Caused by Trypanosoma brucei and transmitted by the tsetse fly.
• American Trypanosomiasis (Chagas Disease) - Agent & Vector: Caused by Trypanosoma cruzi and transmitted by a triatomine ("kissing") bug via contaminated feces.
• Trypanosoma cruzi - Morphology & Diagnosis: The diagnostic stage in the blood is the C-shaped trypomastigote. The tissue stage is the amastigote.
• Chagas Disease - Clinical Signs:
  • Acute Phase: May include a chagoma (nodule at bite site) or Romaña's sign (unilateral eyelid swelling and conjunctivitis).
  • Chronic Phase: Can lead to cardiac complications and digestive issues like megaesophagus and megacolon.

High-Yield Comparisons & Distinctions

• Fungal ID: India Ink vs. Mucicarmine: In diagnosing Cryptococcus, the India Ink stain provides a negative stain to visualize the capsule in a wet mount (CSF), while the Mucicarmine stain positively stains the capsule red in histopathology tissue sections.
• Aspergillus Microscopy: A. fumigatus vs. A. flavus: A. fumigatus has uniseriate phialides on the upper part of the vesicle. A. flavus has biseriate phialides that cover the entire vesicle and a roughened conidiophore.
• Yeast Treatment: Oral Thrush vs. Candidemia: Mild oral thrush (infants) is treated with topical Nystatin or miconazole. Systemic, invasive candidemia requires potent IV drugs like echinocandins or Amphotericin B.
• Dermatophyte Genera: What They Infect: Trichophyton infects all three (skin, hair, nail). Epidermophyton spares the hair. Microsporum spares the nail.
• Nematode Buccal Cavity: Hookworm vs. Strongyloides: The rhabditiform larva of a Hookworm has a long buccal cavity, while the rhabditiform larva of Strongyloides has a short buccal cavity. This is a key differentiator in stool exams.
• Nematode Clinical Clue: Rectal Prolapse vs. Larva Currens: Rectal prolapse in a child with heavy worm burden points toward Trichuris trichiura. A rapidly moving, serpiginous rash (larva currens) is pathognomonic for Strongyloides stercoralis.
• Pinworm vs. Other STH Diagnosis: Diagnosis of Pinworm (Enterobius) requires a Scotch tape test of the perianal region. Diagnosis of Ascaris, Trichuris, and Hookworm relies on finding eggs in a stool sample.
• Parasite Diagnostic Stage: Larva vs. Egg: In stool analysis for intestinal nematodes, the diagnostic stage for Strongyloides is the larva, while for Ascaris, Trichuris, and Hookworm, it is the egg.
• Microfilariae Tail Nuclei: Wuchereria vs. Brugia: The microfilaria of Wuchereria bancrofti has no nuclei in its tail tip. The microfilaria of Brugia malayi has terminal/subterminal nuclei in its tail tip.
• Cestode Infection: Adult Worm vs. Larva: Ingesting the larval stage of Taenia (cysticerci in undercooked meat) leads to an adult tapeworm in the intestine (Taeniasis). Ingesting T. solium eggs leads to the larval stage in human tissues (Cysticercosis), a much more dangerous condition.
• Cestode Scolex: Armed vs. Unarmed: The scolex of Taenia solium (pork tapeworm) is "armed" with a rostellum and hooklets. The scolex of Taenia saginata (beef tapeworm) is "unarmed" and has no hooklets.
• Amebiasis Treatment: Symptomatic vs. Asymptomatic: Symptomatic amebic colitis/abscess requires a tissue-active drug like Metronidazole. An asymptomatic person passing cysts requires a luminal-active drug like Diloxanide furoate to prevent transmission.
• Trypanosomiasis Vectors: Tsetse Fly vs. Triatomine Bug: African Sleeping Sickness (T. brucei) is transmitted by the tsetse fly. American Chagas Disease (T. cruzi) is transmitted by the triatomine bug.
• Blood Flagellate Stages in Humans: Leishmania vs. Trypanosoma: In human hosts, the intracellular stage of Leishmania is the amastigote. For Trypanosoma, the intracellular stage is also the amastigote (in tissues for T. cruzi), but the stage found in the bloodstream is the trypomastigote.
• Hookworm Species ID: Teeth vs. Plates: Ancylostoma duodenale has teeth in its buccal capsule. Necator americanus has cutting plates.

QA

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FUNGAL INFECTIONS

CANDIDA

1. As a member of normal human flora, where does Candida colonize and what type of infection risk does it pose? | Mucosal surfaces; endogenous infection risk.
2. Of the 314+ species in the Candida genus, approximately how many are known to cause candidiasis? | Fewer than 20.
3. What is the most prevalent systemic mycosis? | Candidiasis.
4. What are the five most common causative agents of candidiasis? | 1. C. albicans
   2. C. parapsilosis
   3. C. glabrata
   4. C. tropicalis
   5. C. krusei

Candida albicans

5. What factors can cause C. albicans to convert from a commensal to a pathogen? | The host's immune or endocrine status.
6. Describe the key morphological features of C. albicans. | Polymorphic (budding yeast, pseudohyphae, true hyphae), Gram-positive, 10-12 μm.
7. What transcription repressor is needed for C. albicans to maintain its yeast form? | NRg1.
8. What are two key characteristics used for laboratory identification of C. albicans? | Production of germ tubes and terminal chlamydospores.
9. The Germ Tube Test is based on the principle that its formation is associated with an increase in what? | Increased protein and RNA synthesis.
10. What defines a positive Germ Tube Test, and what are two species that show this? | A short hyphal extension with no constriction at its origin; Candida albicans and Candida dubliniensis.
11. What defines a negative Germ Tube Test, and what are two species that show this? | No hyphal extension or an extension constricted at the origin; C. tropicalis and C. glabrata.

Candidiasis

12. What are the risk factors for invasive candidiasis in non-neutropenic patients? (5) | Anatomical disruption, ICU stays, intravascular catheters, TPN, and antibiotic use.
13. What are the risk factors for invasive candidiasis in neutropenic cancer patients? (3) | Mucosal ulceration, intravascular catheters, and cytotoxic/immunosuppressive drugs.
14. What are two community risk factors for invasive candidiasis? | Hemodialysis and diabetes.
15. What are some of the other clinical forms of invasive candidiasis? (Name 3+) | Bone & Joint, Endocarditis, Endophthalmitis, Renal, CNS infection, Peritonitis, UTI.
16. What is the underlying cause of the rare disease Chronic Mucocutaneous Candidiasis? | A genetic defect in T-cell responsiveness to Candida.

Candida Diagnosis & Treatment

17. What methods are used to diagnose Candida infections? | Morphology on Gram stain, culture on Sabouraud dextrose agar, and biochemical tests.
18. Why is speciation of Candida clinically important? | Due to significant antifungal resistance among different species.
19. How is mild versus moderate-to-severe oral candidiasis treated in adults? | Mild: clotrimazole troches or miconazole buccal tablets.
    Moderate/Severe: oral Fluconazole.
20. How is oral thrush treated in infants? | Oral miconazole or Nystatin solution.
21. What is the standard treatment for esophageal candidiasis? | Oral fluconazole.
22. What is a crucial step in treating candidemia from a central venous catheter? | Remove the central venous catheter.
23. What is the drug of choice for candidemia in non-neutropenic patients? | An echinocandin (e.g., micafungin, caspofungin).
24. What is the drug of choice for candidemia in neutropenic patients? | An echinocandin.
25. What is concerning about the emerging pathogen Candida auris? | It is often multidrug-resistant and has caused healthcare-associated outbreaks.
26. Why is Candida krusei a concern in fungal infections? | Its relative intrinsic resistance to azoles and other antifungal drugs.

CRYPTOCOCCOSIS

27. Cryptococcosis is a subacute or chronic infection most often involving which body system and is considered a defining illness for what condition? | CNS; AIDS-defining illness.
28. Compare C. neoformans and C. gattii in terms of distribution, source, and typical host. | C. neoformans: Worldwide, pigeon feces, immunocompromised hosts.
    C. gattii: Tropical/subtropical, Eucalyptus trees, normal hosts.
29. How does Cryptococcus infection occur, and what is the most common site of dissemination? | Inhalation of particles; CNS is the most common site of dissemination.
30. What is the most common initial site of infection in cryptococcosis? | The lungs (pulmonary infection).
31. What is the hallmark laboratory diagnostic test for cryptococcosis? | The India Ink mount of CSF.
32. On Niger seed agar, what is the characteristic culture appearance of Cryptococcus? | Brown colony effect.
33. What special stain is used in histopathology to stain the capsule of Cryptococcus red? | Mucicarmine stain.
34. What are the three treatment phases for severe cryptococcosis? | 1. Induction: Amphotericin B + flucytosine
    2. Consolidation: High-dose fluconazole
    3. Maintenance: Lower-dose fluconazole

SUPERFICIAL & CUTANEOUS MYCOSES

35. What layer of the skin or part of the hair do superficial mycoses affect? | The outermost layer of the skin (stratum corneum) or hair shafts.
36. What are the four types of superficial mycoses and their causative agents? | 1. Pityriasis Versicolor: Malassezia spp.
    2. White Piedra: Trichosporon spp.
    3. Black Piedra: Piedraia hortae
    4. Tinea Nigra: Hortaea werneckii
37. Cutaneous mycoses (dermatophytes) are confined to what layers and what enzyme do they produce? | Non-living outer layers of skin, hair, and nails; produce keratinases.
38. What is the fastest and simplest diagnostic test for dermatophytes? | A skin scraping with KOH preparation.
39. Which areas do the three dermatophyte genera infect? (Trichophyton, Microsporum, Epidermophyton) | Trichophyton: Skin, hair, nails.
    Microsporum: Hair and skin.
    Epidermophyton: Skin and nails.
40. What is the characteristic microscopic appearance of Trichophyton rubrum? | Pyriform microconidia arranged like “birds on a wire.”
41. What is the characteristic microscopic appearance of Trichophyton tonsurans? | Varied microconidia, including “match stick” shapes and balloon forms.
42. Hairs infected with Microsporum canis have what unique property, and what is its microscopic appearance? | Fluoresce bright green under a Wood's light; large, spindle-shaped, spiny macroconidia.
43. What are the two key microscopic characteristics of Epidermophyton floccosum? | Absence of microconidia and presence of smooth, club-shaped macroconidia.
44. A severe form of tinea capitis called Favus is characterized by what clinical sign? | Scutulum (yellow, cup-shaped crust).
45. In Tinea Cruris (Jock Itch), which parts of the groin area are typically spared? | The scrotum and penis.
46. What type of antifungal agents are often ineffective against Tinea Unguium (Onychomycosis)? | Topical antifungal agents.
47. The "moccasin type" of Tinea Pedis presents with what distribution and is often associated with what other finding? | Moccasin-like distribution; associated with “two feet, one hand” presentation.
48. What is the classic “spaghetti-and-meatballs” appearance on microscopy associated with? | Malassezia species.
49. What three conditions are associated with Malassezia species? | Tinea Versicolor, Neonatal Acne, Seborrheic Dermatitis.
50. For onychomycosis, why is oral therapy generally more effective than topical therapy? | Due to the nail plate barrier.

FILAMENTOUS FUNGI

51. What are the two most common pathogens causing invasive aspergillosis? | Aspergillus fumigatus and Aspergillus flavus.
52. What are the four main pathogenic forms of aspergillosis? | 1. Aspergilloma
    2. Invasive Aspergillosis
    3. Allergic Aspergillosis
    4. Aflatoxicosis
53. What is the characteristic microscopic appearance of Aspergillus fumigatus? | Uniseriate conidial heads with phialides on the upper two-thirds of the vesicle.
54. What is the characteristic microscopic appearance of Aspergillus flavus? | Biseriate conidial heads and coarsely roughened conidiophores.
55. What is the characteristic microscopic appearance of Aspergillus niger? | Biseriate, large, globose, radiate conidial heads producing black conidia.
56. What is the drug of choice for treating invasive aspergillosis? | Amphotericin B.
57. In which patient populations does mucormycosis typically occur? | Patients with diabetic ketoacidosis, malignancy, severe burns, or trauma.
58. Mucormycosis is pathologically characterized by acute inflammation and what other process that leads to tissue necrosis? | Angioinvasion (fungal invasion of blood vessels).
59. What are the common causative agents of mucormycosis? (Name 2+) | Rhizopus, Lichtheimia, and Rhizomucor.

PARASITIC INFECTIONS

INTESTINAL NEMATODES

60. Where in the intestines do Ascaris and Trichuris typically inhabit, respectively? | Ascaris: small intestine.
    Trichuris: cecum/colon.
61. What are three examples of intestinal nematodes that are Aphasmids (have no phasmids)? | Trichinella spiralis, Trichuris trichiura, Capillaria philippinensis.
62. What are four examples of intestinal nematodes that are Phasmids (have phasmids)? | Strongyloides, Enterobius, Ascaris, Hookworms.
63. How is trichinosis (caused by Trichinella spiralis) transmitted, and what is unique about the human host role? | Eating raw/insufficiently cooked pork; humans serve as both definitive and intermediate hosts.
64. What is the definitive diagnostic test for Trichinella spiralis? | A muscle biopsy to find encysted larvae.
65. What is the characteristic morphology of a Trichuris trichiura (Whipworm) egg? | Barrel-shaped with polar plugs on each end.
66. Heavy infections with Trichuris trichiura can cause dysentery and what other specific manifestation, especially in children? | Rectal prolapse.
67. Capillaria philippinensis is associated with what endemic area and dietary habit? | The Philippines; eating raw freshwater fish.
68. Intestinal capillariasis (due to C. philippinensis) causes malabsorption and what potentially fatal condition? | A protein-losing enteropathy.
69. How do the eggs of Capillaria philippinensis appear? | Peanut-shaped with flattened bipolar plugs.
70. The life cycle of Ascaris lumbricoides involves ingestion of embryonated eggs and a larval migration through which organ? | The lungs.
71. How does human infection with Hookworm occur? | Filariform larvae in soil penetrate intact skin.
72. How can the rhabditiform larvae of Hookworm and Strongyloides be differentiated based on their buccal cavity? | Hookworm: long buccal cavity.
    Strongyloides: short buccal cavity.
73. How can Ancylostoma duodenale and Necator americanus be differentiated by their mouthparts? | A. duodenale: two pairs of ventral teeth.
    N. americanus: a pair of semilunar cutting plates.
74. Chronic infection with hookworm characteristically leads to what type of anemia? | Iron deficiency anemia.
75. What unique feature of Strongyloides stercoralis allows infection to persist for decades? | Autoinfection.
76. What is the characteristic dermatologic manifestation of Strongyloides stercoralis? | Larva currens.
77. What is the diagnostic stage of Strongyloides stercoralis found in the stool? | Larvae (rhabditiform), not eggs.
78. What is the hallmark symptom of Enterobius vermicularis (Pinworm) infection? | Intense perianal pruritus (pruritus ani).
79. What is the specific diagnostic method used for Enterobius vermicularis (Pinworm)? | The perianal cellulose tape swab (Scotch tape test).
80. What is the characteristic morphology of an Enterobius vermicularis egg? | Asymmetrical, being flattened on one side (D-shaped or lopsided).

TISSUE NEMATODES (FILARIA)

81. What two nematode species cause Lymphatic Filariasis? | Wuchereria bancrofti and Brugia malayi.
82. How is Lymphatic Filariasis transmitted? | By mosquito vectors.
83. What elicits the most severe inflammation and lymphatic damage in Lymphatic Filariasis? | Dead or dying adult worms.
84. What are the chronic manifestations of Lymphatic Filariasis? (3) | Lymphedema, elephantiasis, and hydrocele.
85. What is the most common chronic manifestation of bancroftian filariasis (W. bancrofti)? | Hydrocele.
86. What is the gold standard for diagnosing Lymphatic Filariasis? | Detection of circulating filarial antigen (CFA) via immunochromatographic test (ICT).
87. For microscopic diagnosis of W. bancrofti, when should blood be collected? | Between 8 PM and 4 AM.
88. How are the microfilariae of W. bancrofti and B. malayi differentiated based on their tails? | W. bancrofti: nuclei do not extend to the tail tip.
    B. malayi: nuclei extend to the tail tip.
89. How is the elephantiasis of Lymphatic Filariasis managed? | Supportive care: hygiene, elevation, and exercise.
90. How do humans acquire Toxocariasis? | By ingesting eggs from dog (T. canis) or cat (T. cati) roundworms.
91. What are the two main forms of Toxocariasis? | Visceral larva migrans and ocular larva migrans.

CESTODES (TAPEWORMS)

92. For Taenia solium (pork tapeworm), what are the roles of the human host? | Humans are the only definitive host and can also be an intermediate host.
93. What is cysticercosis, and what is its most serious form? | Infection with the larval stage of T. solium; neurocysticercosis is the most serious form.
94. For Taenia saginata (beef tapeworm), what is the role of the human host? | Humans are the only definitive host.
95. Can the eggs of T. solium and T. saginata be differentiated morphologically? | No, they are morphologically indistinguishable.
96. How are the scolices and uteri of T. solium and T. saginata differentiated? | T. solium: scolex has hooklets, <13 uterine branches.
    T. saginata: scolex has no hooklets, >13 uterine branches.
97. What disease is caused by Echinococcus granulosus? | Hydatid disease.
98. What is a hydatid cyst and where does it most commonly form? | The larval stage of E. granulosus; most commonly in the liver.

PROTOZOA

99. What disease is caused by Entamoeba histolytica? | Amebic colitis and potentially amebic liver abscess.
100. How is infection with Entamoeba histolytica acquired and what are the life cycle stages in the human? | Ingesting cysts (infective stage); cysts develop into trophozoites (invasive stage).
101. How is a diagnosis of Entamoeba histolytica made from a stool sample? | Finding trophozoites (may contain ingested RBCs) or cysts.
102. How is amebiasis treated for symptomatic vs. asymptomatic patients? | Symptomatic: a tissue agent like Metronidazole.
     Asymptomatic: a luminal agent like Diloxanide furoate.
103. What is the vector for Leishmaniasis, and what stage is injected into the human? | Phlebotomus sandfly; promastigote stage.
104. In human macrophages, what does the promastigote of Leishmania transform into? | Amastigotes.
105. What are the three clinical forms of Leishmaniasis? | Cutaneous, Mucocutaneous, and Visceral (Kala-azar).
106. What is the causative agent and vector for African Trypanosomiasis (Sleeping Sickness)? | Agent: Trypanosoma brucei; Vector: tsetse fly.
107. What is the causative agent and vector for American Trypanosomiasis (Chagas Disease)? | Agent: Trypanosoma cruzi; Vector: triatomine ("kissing") bug.
108. What are the diagnostic stages of Trypanosoma cruzi in the blood and in the tissue? | Blood: C-shaped trypomastigote.
     Tissue: amastigote.
109. What are the key clinical signs of the acute and chronic phases of Chagas Disease? | Acute: chagoma or Romaña's sign.
     Chronic: megaesophagus and megacolon.

High-Yield Comparisons & Distinctions

110. In diagnosing Cryptococcus, compare the use of India Ink vs. Mucicarmine stain. | India Ink: Negative stain for capsule in wet mount (CSF).
     Mucicarmine: Positively stains capsule red in tissue sections.
111. Microscopically, how do you differentiate Aspergillus fumigatus from Aspergillus flavus? | A. fumigatus: Uniseriate phialides on upper part of vesicle.
     A. flavus: Biseriate phialides on entire vesicle, roughened conidiophore.
112. Contrast the treatment for mild oral thrush in infants versus systemic, invasive candidemia. | Oral Thrush: Topical Nystatin.
     Candidemia: IV echinocandins or Amphotericin B.
113. For the main dermatophyte genera, which parts do they infect? | Trichophyton: infects skin, hair, and nail.
     Epidermophyton: spares the hair.
     Microsporum: spares the nail.
114. How are the rhabditiform larvae of Hookworm and Strongyloides differentiated? | Hookworm: has a long buccal cavity.
     Strongyloides: has a short buccal cavity.
115. Contrast the key clinical clues for Trichuris trichiura vs. Strongyloides stercoralis. | Trichuris: Rectal prolapse.
     Strongyloides: Larva currens.
116. Contrast the diagnostic method for Pinworm (Enterobius) versus other common intestinal nematodes like Ascaris. | Pinworm: Scotch tape test.
     Ascaris, Trichuris, Hookworm: finding eggs in stool.
117. For intestinal nematodes, what is the diagnostic stage found in stool for Strongyloides vs. others like Ascaris? | Strongyloides: larva.
     Ascaris, Trichuris, Hookworm: egg.
118. How are the microfilariae of Wuchereria bancrofti and Brugia malayi differentiated? | W. bancrofti: has no nuclei in its tail tip.
     B. malayi: has terminal/subterminal nuclei in its tail tip.
119. Compare the outcome of ingesting Taenia larvae versus ingesting T. solium eggs. | Larvae (in meat) -> Adult tapeworm (Taeniasis).
     T. solium eggs -> Larval stage in tissues (Cysticercosis).
120. How can you differentiate the scolex of Taenia solium from Taenia saginata? | T. solium: "armed" with a rostellum and hooklets.
     T. saginata: "unarmed," has no hooklets.
121. Contrast the treatment for symptomatic amebic colitis versus an asymptomatic cyst passer. | Symptomatic: tissue-active drug (Metronidazole).
     Asymptomatic: luminal-active drug (Diloxanide furoate).
122. What are the respective vectors for African Sleeping Sickness and American Chagas Disease? | African: tsetse fly.
     American: triatomine bug.
123. In human hosts, what is the intracellular stage of Leishmania vs. the bloodstream stage of Trypanosoma? | Leishmania (intracellular): amastigote.
     Trypanosoma (bloodstream): trypomastigote.
124. How are the hookworm species Ancylostoma duodenale and Necator americanus identified? | A. duodenale: has teeth.
     N. americanus: has cutting plates.

5 - Viral

gemini 3 flash

Summary

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I. Human Immunodeficiency Virus (HIV)

• HIV Tropism: Target cell selection is determined by the envelope glycoprotein (Env), specifically gp120 binding to CD4 molecules on T lymphocytes.
• HIV-1 Detection: Glycoprotein gp41 is highly immunogenic and is the primary antigen used to detect HIV-1 antibodies.
• HIV Vaccine Obstacles: The high heterogeneity of gp120 is the major obstacle in establishing an effective vaccine.
• HIV-2 Diagnosis: Difficult due to genetic differences from HIV-1; necessitates a combination screening test for both peptides. Standard HIV-1 confirmatory assays (immunoblot) may give indeterminate results.
• HIV Pediatric Disease Patterns:
  1. First Pattern (Rapid): 15–25% of cases; onset of AIDS in first months; median survival 6–9 months if untreated.
  2. Second Pattern (Slower): 60–80% of cases; viral load peaks at 2–3 months; median survival 6 years.
  3. Third Pattern (Long-term): <5% of cases; minimal progression for >8 years; includes "elite survivors" with undetectable virus.
• HIV Transmission: Primarily vertical transmission in pediatric patients (<15 years), occurring intrauterine (20-30%), intrapartum, or postpartum (breastmilk). Perinatal ART treatment reduces risk to <2%.
• Pneumocystis jiroveci (PJP): The most common opportunistic infection in pediatric HIV; peak incidence at 3–6 months; highest mortality in infants <1 year.
• PJP Presentation and Treatment: Presents with acute fever, tachypnea, and marked hypoxemia. First-line therapy: TMP-SMX (15-20 mg/kg/day); add Corticosteroids if PaO₂ <70 mm Hg.
• Mycobacterium avium-intracellulare (MAC): Disseminated disease in severe immunosuppression (CD4 <100); diagnosed via blood/tissue culture. Treatment: Clarithromycin/Azithromycin + Ethambutol.
• Oral Candidiasis: The most common fungal infection in HIV-infected children. Treatment: Oral Nystatin or Fluconazole. If it involves the esophagus (dysphagia/anorexia), use oral Fluconazole.
• Cytomegalovirus (CMV): Occurs with CD4 <50; manifests as retinitis or pneumonitis. Drugs of choice: Ganciclovir and Foscarnet.
• Immune Reconstitution Inflammatory Syndrome (IRIS): Paradoxical inflammatory response to subclinical infections after starting ART. Managed with NSAIDs or Corticosteroids.
• Other HIV Manifestations:
  • Respiratory: LIP (lymphocytic interstitial pneumonia) is the most common chronic lower tract abnormality.
  • Renal: Nephrotic syndrome is the most common manifestation of pediatric renal disease.
• HIV Diagnosis in Infants: IgG antibody tests are not definitive before 24 months due to passive transfer of maternal antibodies.
• Infant HIV Exclusion: Non-breastfed infants require two or more negative virologic (PCR) tests, with one at ≥1 month and one at ≥4 months for definitive exclusion.
• ART Drug Classes:
  • NRTIs: Chain terminators (e.g., Didanosine, Lamivudine).
  • NNRTIs: Cause conformational change in reverse transcriptase (e.g., Nevirapine, Efavirenz).
  • Protease Inhibitors (PIs): Act late in the replicative cycle.
  • Integrase Inhibitors (INSTIs): Block genome incorporation (e.g., Dolutegravir).
  • Fusion Inhibitors: Bind to gp41 (Enfuvirtide).

II. Dengue and Chikungunya

• Dengue Vector: Primarily Aedes aegypti (daytime biter, breeds in clear/stored water), also A. albopictus.
• Dengue Fever Presentation: Biphasic fever ("Back-break fever"), retroorbital pain, pulse rate slow relative to fever.
• Dengue Hemorrhagic Fever (DHF) Criteria (WHO):
  1. Fever 2-7 days.
  2. Hemorrhagic manifestations.
  3. Thrombocytopenia (<100,000/uL).
  4. Objective Capillary Leak (Hct >20% rise, pleural effusion, ascites, or hypoalbuminemia).
• Dengue Shock Syndrome (DSS): Criteria for DHF plus signs of circulatory failure: Hypotension, tachycardia, and narrow pulse pressure (<20 mmHg).
• Herman's Rash: Characteristic dengue rash described as "islands of white in a sea of red"; non-blanching; appears 1-2 days after defervescence.
• Dengue Warning Signs (CLLLAMP):
  • Clinical fluid accumulation.
  • Liver enlargement (>2 cm).
  • Lethargy/restlessness.
  • Laboratory: High Hct with rapid platelet drop.
  • Abdominal pain/tenderness.
  • Mucosal bleed.
  • Persistent vomiting.
• Dengue Diagnosis: NS1 Antigen (positive at 24 hrs), IgM (day 5 to 3 months), IgG (past infection). Gold Standard: PCR or viral culture.
• Dengue Management: Fluids to counteract hemoconcentration. Aspirin is strictly contraindicated due to hemostasis effects. In reabsorptive phase, watch for Hypervolemia (indicated by Hct decrease with wide pulse pressure).
• Chikungunya Characteristics: High fever (>38.9°C), symmetrical/disabling joint pain, maculopapular rash, and conjunctival injection. 12% have residual joint symptoms 3 years later.

III. Influenza

• Influenza Pathogenesis: Infects ciliated columnar epithelial cells; HA attaches to sialic acid residues. Results in loss of ciliary function and lytic infection.
• Antigenic Drift: Minor point mutations in the HA gene; occurs in both A and B types; reason for annual vaccine updates.
• Antigenic Shift: Major reassortment of viral segments; occurs only in Influenza A; results in new subtypes (e.g., H1N1, H2N2) and potential pandemics.
• Complications in Children: Acute otitis media (25%) and pneumonia (primary viral or secondary bacterial, e.g., S. aureus).
• Influenza High-Risk Groups: Children <5 years (highest risk <2 years), elderly, asthmatics, and those with chronic diseases (CKD, DM).
• Neuraminidase Inhibitors (NAIs): Oseltamivir (oral, birth and older) and Zanamivir (inhaled, 7 years+).
• Influenza Chemoprophylaxis: Recommended for high-risk unvaccinated individuals or institutional outbreaks if started within 48 hours of exposure. Peramivir and Baloxavir are NOT for prophylaxis.

IV. Rotavirus

• Epidemiology: The single most important cause of severe dehydrating diarrhea in early childhood; most severe between 3-24 months.
• Structure: Reoviridae family; wheel-like; 11 segments of dsRNA. Group A is the common human pathogen.
• Pathogenesis: Infects/destroys villi of the small intestine → villi blunting → decreased absorption of salt/water → gastroenteritis.
• Clinical Triad: Fever, vomiting, followed by frequent watery stools. Symptoms: "suka-libang-suka-libang" (vomit-defecate).
• Diagnosis: Stools are free of blood and leukocytes. Leading lab finding: Isotonic dehydration with metabolic acidosis.
• Treatment: Mainstay is Oral Rehydration Salts (ORS) to avoid/treat dehydration. Maintenance of nutrition is a secondary goal. No role for antivirals.

V. Coronavirus (SARS, MERS, and Common)

• SARS-CoV: Utilizes ACE-2 receptor; reservoirs are bats; lineage B Betacoronavirus.
• MERS-CoV: Utilizes Dipeptidyl peptidase 4 (DPP4) and CEACAM5; transmitters include camels and bats; lineage C Betacoronavirus.
• SARS vs. MERS Transmission: SARS is highly infectious via mucous membranes/droplets. MERS is less communicable but has a high mortality rate (~35%).
• Pediatric Manifestations: Coronavirus NL63 is a known cause of Croup in children <3 years. Outbreaks in NICU can cause necrotizing enterocolitis.
• MERS-CoV Presentation: Often includes Acute Kidney Injury (AKI) and gastrointestinal symptoms (1/3 of patients), alongside severe respiratory distress.
• Diagnosis: Wide use of multiplex RT-PCR. MERS-CoV laboratory confirmation relies on real-time RT-PCR targeting the upE (upstream envelope) gene.
• Treatment: Primarily supportive. No specific antiviral agents recommended; Ribavirin was used in 2003 for SARS but remains inconclusive.

XI. Comparative Differentiations for Exams

1. HIV-1 vs. HIV-2: HIV-1 is the global pandemic strain; HIV-2 (West African focus) has the vpx gene and lacks the vpu gene.
2. PJP vs. MAC (HIV): PJP is the most common pediatric opportunistic infection (presents acutely with hypoxemia); MAC occurs in severe immunosuppression (CD4 <100) and presents with systemic fever/night sweats.
3. Dengue vs. Chikungunya (Joints): Dengue causes myalgia/arthralgia (Back-break); Chikungunya causes severe, symmetrical, disabling polyarthralgia that can persist for years.
4. Dengue vs. Chikungunya (Labs): Dengue is characterized by hemoconcentration (Hct increase) and prominent leukopenia; Chikungunya is characterized by lymphopenia and lacks significant plasma leakage/Hct rise.
5. Dengue vs. Chikungunya (Rash): Dengue has Herman's Rash (non-blanching islands of white); Chikungunya can present with aphthous-like ulcers and vesiculobullous rashes.
6. Antigenic Drift vs. Shift: Drift is minor mutation (point mutations) in HA/NA (both Influ A and B); Shift is major reassortment (only Influ A), leading to pandemics.
7. Inactivated vs. Live Influenza Vaccine: Every year in the Philippines, only inactivated vaccines are usually used/available.
8. SARS-CoV vs. MERS-CoV Receptors: SARS uses ACE-2; MERS uses DPP4.
9. Rotavirus vs. Amoebiasis Stool: Rotavirus stool is watery/free of blood/WBCs; Amoebiasis is scanty, mucoid, greenish, and has a fishy odor with tenesmus.
10. Aedes aegypti vs. Aedes albopictus: A. aegypti is the principal urban vector; A. albopictus is highly adaptive to cooler temperatures and survivors freezing.
11. HIV Virologic vs. Antibody Test (Infants): Antibody tests are unreliable <24 months (passive maternal transfer); Virologic PCR tests are mandatory for diagnosis in infants.
12. DHF vs. DSS: DHF requires fever, bleeding, low platelets, and capillary leak; DSS is DHF plus narrow pulse pressure (<20mmHg) or hypotension.
13. Isotonic vs. Hypotonic Dehydration: Rotavirus is most commonly associated with Isotonic dehydration with acidosis.
14. Oseltamivir vs. Adamantanes: Oseltamivir (Tamiflu) treats both Influ A and B; Amantadine is only for Influ A and now has widespread resistance (not recommended).

QA

Gemini 2.5 pro

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I. Human Immunodeficiency Virus (HIV)

1. What determines HIV's structure and tropism, and what cells does it target? | Envelope glycoprotein (Env); Tropism for CD4+ T cells, macrophages, and microglial cells.
2. What is the function of HIV's gp120 protein? | Target cell binding (CD4).
3. What is the function of HIV's gp41 protein? | It is the transmembrane subunit and is immunogenic.
4. What is the precursor for HIV's gp120 and gp41 proteins? | gp160.
5. What are the key features of the HIV-1 Genome? | It is a Retroviridae with 2 copies of ssRNA, regulated by long terminal repeats.
6. What does the GAG gene in HIV-1 code for? | The viral core (p24, p17).
7. What does the POL gene in HIV-1 code for? | Enzymes (protease, integrase).
8. What does the ENV gene in HIV-1 code for? | The envelope (gp120, gp41).
9. What are the key characteristics of HIV-2? | Common in Western Africa; rare in children.
10. What genes are unique to HIV-2 compared to HIV-1? | It has the vpx gene and no vpu gene.
11. What specifically determines HIV tropism for T lymphocytes? | The envelope glycoprotein (Env), specifically gp120 binding to CD4 molecules.
12. What is the primary antigen used for HIV-1 detection via antibody tests? | Glycoprotein gp41, which is highly immunogenic.
13. What is the major obstacle in creating an effective HIV vaccine? | The high heterogeneity of gp120.
14. Why is HIV-2 diagnosis difficult and what is required? | Difficult due to genetic differences from HIV-1; necessitates a combination screening test.
15. Describe the first, rapid pediatric HIV disease pattern. | 15–25% of cases; AIDS onset in first months; median survival of 6–9 months if untreated.
16. Describe the second, slower pediatric HIV disease pattern. | 60–80% of cases; viral load peaks at 2–3 months; median survival of 6 years.
17. Describe the third, long-term pediatric HIV disease pattern. | <5% of cases; show minimal progression for >8 years.
18. What is the primary mode of HIV transmission in pediatric patients? | Vertical transmission (intrauterine, intrapartum, or postpartum).
19. What is the most common opportunistic infection in pediatric HIV? | Pneumocystis jiroveci (PJP).
20. What is the presentation and first-line therapy for PJP? | Presents with acute fever, tachypnea, and marked hypoxemia; First-line therapy is TMP-SMX.
21. In PJP treatment, when should Corticosteroids be added? | If PaO₂ is less than 70 mm Hg.
22. When does disseminated MAC infection occur in HIV patients? | In severe immunosuppression (CD4 <100).
23. What is the treatment for MAC infection in HIV patients? | Clarithromycin/Azithromycin + Ethambutol.
24. What is the most common fungal infection in HIV-infected children? | Oral Candidiasis.
25. How is Oral Candidiasis treated in HIV-infected children? | Oral Nystatin or Fluconazole.
26. CMV infection in HIV patients occurs at what CD4 count and what are the drugs of choice? | Occurs with CD4 <50; drugs of choice are Ganciclovir and Foscarnet.
27. What is Immune Reconstitution Inflammatory Syndrome (IRIS)? | A paradoxical inflammatory response to subclinical infections after starting ART.
28. What is the most common chronic lower respiratory tract abnormality in pediatric HIV? | LIP (lymphocytic interstitial pneumonia).
29. What is the most common manifestation of pediatric renal disease in HIV? | Nephrotic syndrome.
30. Why are IgG antibody tests not definitive for HIV diagnosis in infants? | Due to the passive transfer of maternal antibodies.
31. How is HIV definitively excluded in a non-breastfed infant? | Two or more negative virologic (PCR) tests, with one at ≥1 month and one at ≥4 months.
32. What is the mechanism of NRTIs? | They are chain terminators (e.g., Didanosine, Lamivudine).
33. What is the mechanism of NNRTIs? | They cause a conformational change in reverse transcriptase (e.g., Nevirapine, Efavirenz).
34. What is the mechanism of Protease Inhibitors (PIs)? | They act late in the replicative cycle.
35. What is the mechanism of Integrase Inhibitors (INSTIs)? | They block genome incorporation into the host cell (e.g., Dolutegravir).
36. What is the mechanism of Fusion Inhibitors? | They bind to gp41 (e.g., Enfuvirtide).

II. Dengue and Chikungunya

37. What is the etiology of Dengue Fever? | Flavivirus (Serotypes 1,2,3,4).
38. What is the etiology of Chikungunya? | Alphavirus (Togaviridae family).
39. What is the classic rash finding in Dengue Fever? | Herman’s Rash, described as "islands of white in a sea of red."
40. What is the classic clinical finding in Chikungunya? | Severe, symmetrical polyarthralgia.
41. What are the laboratory hallmarks of Dengue Fever? | Leukopenia, Thrombocytopenia, and Hemoconcentration (Hct >20% increase).
42. What are the laboratory hallmarks of Chikungunya? | Lymphopenia and persistent joint pain.
43. What is the underlying pathophysiology of Dengue Hemorrhagic Fever? | Capillary Leak Syndrome.
44. What is the underlying pathophysiology of joint symptoms in Chikungunya? | Inflammatory arthritis/tenosynovitis.
45. What is the primary vector for Dengue? | Aedes aegypti.
46. What is the classic presentation of Dengue Fever? | Biphasic fever ("Back-break fever"), retroorbital pain, and pulse rate that is slow relative to the fever.
47. What are the 4 WHO criteria for Dengue Hemorrhagic Fever (DHF)? | 1) Fever
    2) Hemorrhagic manifestations
    3) Thrombocytopenia (<100,000/uL)
    4) Objective Capillary Leak.
48. What defines Dengue Shock Syndrome (DSS)? | The criteria for DHF plus signs of circulatory failure, like narrow pulse pressure (<20 mmHg).
49. Describe Herman's Rash of Dengue. | Non-blanching "islands of white in a sea of red" that appears 1-2 days after defervescence.
50. What are the Dengue warning signs (CLLLAMP)? | Clinical fluid accumulation
    Liver enlargement
    Lethargy
    Lab changes
    Abdominal pain
    Mucosal bleed
    Persistent vomiting.
51. How is Dengue diagnosed, and what is the gold standard? | NS1 Antigen (early) or IgM (late); Gold Standard is PCR or viral culture.
52. What is the mainstay of Dengue management and what drug is contraindicated? | Fluids to counteract hemoconcentration; Aspirin is strictly contraindicated.
53. During the reabsorptive phase of Dengue, what complication must be watched for? | Hypervolemia, indicated by a decrease in Hct with a wide pulse pressure.
54. What are the key features of a Chikungunya infection? | High fever, symmetrical/disabling joint pain, maculopapular rash, and conjunctival injection.

III. Influenza

55. Compare the pandemic potential of Influenza A vs. Influenza B. | Influenza A has high potential for global pandemics; Influenza B causes seasonal epidemics only.
56. What types of antigenic variation occur in Influenza A? | Both antigenic shift and drift.
57. What type of antigenic variation occurs in Influenza B? | Only antigenic drift.
58. What is the host range for Influenza A? | Humans, birds, and other mammals (has animal reservoirs).
59. What is the host range for Influenza B? | Primarily humans.
60. How are Influenza A subtypes designated? | Based on surface proteins HA (Hemagglutinin) and NA (Neuraminidase).
61. How are Influenza B viruses designated? | By lineages (Yamagata and Victoria).
62. What is the pathogenesis of Influenza? | It infects ciliated columnar epithelial cells after HA attaches to sialic acid residues.
63. What is Antigenic Drift? | Minor point mutations in the HA gene, occurring in both Influenza A and B.
64. What is Antigenic Shift? | Major reassortment of viral segments that occurs only in Influenza A, leading to new subtypes.
65. What are common complications of Influenza in children? | Acute otitis media and pneumonia.
66. Who are considered high-risk groups for severe Influenza? | Children <5 years, the elderly, asthmatics, and those with chronic diseases.
67. Name two Neuraminidase Inhibitors (NAIs). | Oseltamivir (oral) and Zanamivir (inhaled).
68. When is Influenza chemoprophylaxis recommended? | For high-risk unvaccinated individuals or institutional outbreaks if started within 48 hours of exposure.
69. Which drugs for Influenza are not recommended for prophylaxis? | Peramivir and Baloxavir.

IV. Rotavirus

70. What is the epidemiologic significance of Rotavirus in early childhood? | It is the single most important cause of severe dehydrating diarrhea.
71. Describe the structure of Rotavirus. | A wheel-like virus of the Reoviridae family with 11 segments of dsRNA.
72. What is the pathogenesis of a Rotavirus infection? | It infects and destroys villi of the small intestine, causing villi blunting and decreased absorption.
73. What is the clinical triad of Rotavirus? | Fever, vomiting, followed by frequent watery stools.
74. What are the key diagnostic findings for Rotavirus? | Stools are free of blood and leukocytes; common lab finding is isotonic dehydration with metabolic acidosis.
75. What is the mainstay of treatment for Rotavirus? | Oral Rehydration Salts (ORS).

V. Coronavirus (SARS, MERS, and Common)

76. What is the function of the Spike (S) protein in Coronavirus? | Critical for binding host receptors and facilitating entry.
77. What is the function of the Nucleocapsid (N) protein in Coronavirus? | It is bound to the RNA genome.
78. What is the function of the Membrane (M) protein in Coronavirus? | It is the central organizer of virus assembly and determines envelope shape.
79. What is the function of the Envelope (E) protein in Coronavirus? | It interacts with the M protein to form the viral envelope.
80. What receptor does SARS-CoV use and what is its reservoir? | It utilizes the ACE-2 receptor; reservoirs are bats.
81. What receptor does MERS-CoV use and what are its transmitters? | It utilizes the Dipeptidyl peptidase 4 (DPP4) receptor; transmitters include camels and bats.
82. How does MERS-CoV transmission and mortality compare to SARS-CoV? | MERS is less communicable but has a higher mortality rate (~35%).
83. What is a known pediatric manifestation of Coronavirus NL63? | It is a known cause of Croup in children under 3 years old.
84. What clinical finding, besides respiratory distress, is often part of a MERS-CoV presentation? | Acute Kidney Injury (AKI) and gastrointestinal symptoms.
85. How is MERS-CoV diagnosis confirmed in a laboratory? | By a real-time RT-PCR that targets the upE (upstream envelope) gene.
86. What is the treatment for SARS-CoV and MERS-CoV? | Primarily supportive care.

XI. Comparative Differentiations for Exams

87. Compare HIV-1 vs. HIV-2. | HIV-1: global pandemic strain.
    HIV-2: West African focus, has the vpx gene, lacks the vpu gene.
88. Compare PJP vs. MAC in an HIV patient. | PJP: most common pediatric OI, presents with acute hypoxemia.
    MAC: occurs in severe immunosuppression (CD4 <100), presents with systemic fever.
89. Compare the joint pain in Dengue vs. Chikungunya. | Dengue: myalgia/arthralgia ("Back-break" fever).
    Chikungunya: severe, symmetrical, disabling polyarthralgia that can persist for years.
90. Compare the lab findings in Dengue vs. Chikungunya. | Dengue: hemoconcentration (Hct increase) and prominent leukopenia.
    Chikungunya: prominent lymphopenia, no significant plasma leakage.
91. Compare the rash in Dengue vs. Chikungunya. | Dengue: Herman's Rash (non-blanching islands of white).
    Chikungunya: can present with aphthous-like ulcers and vesiculobullous rashes.
92. Compare Antigenic Drift vs. Shift. | Drift: minor point mutations (in Influ A and B).
    Shift: major segment reassortment (only in Influ A), causing pandemics.
93. Compare Inactivated vs. Live Influenza Vaccine availability in the Philippines. | In the Philippines, only inactivated influenza vaccines are usually used/available each year.
94. Compare the host receptors for SARS-CoV vs. MERS-CoV. | SARS-CoV uses the ACE-2 receptor.
    MERS-CoV uses the DPP4 receptor.
95. Compare the stool characteristics in Rotavirus vs. Amoebiasis. | Rotavirus: watery, free of blood/WBCs.
    Amoebiasis: scanty, mucoid, greenish, and has a fishy odor.
96. Compare Aedes aegypti vs. Aedes albopictus. | A. aegypti: principal urban vector.
    A. albopictus: highly adaptive to cooler temperatures.
97. Compare diagnostic tests for HIV in infants. | Antibody tests: unreliable <24 months (maternal transfer).
    Virologic PCR tests: mandatory for definitive diagnosis in infants.
98. Compare DHF vs. DSS. | DHF: requires fever, bleeding, low platelets, and capillary leak.
    DSS: is DHF plus signs of circulatory shock (e.g., narrow pulse pressure <20mmHg).
99. Compare Isotonic vs. Hypotonic Dehydration in Rotavirus. | Rotavirus is most commonly associated with Isotonic dehydration with acidosis.
100. Compare Oseltamivir vs. Adamantanes for influenza treatment. | Oseltamivir: treats both Influenza A and B.
     Amantadine: only treats Influenza A and has widespread resistance.

5

Summary

text

Gastroesophageal Reflux (GER) and Disease (GERD)

Overview and Comparison

• Epidemiology of GERD: Gastroesophageal reflux disease is the most common esophageal disorder in children, with an increasing incidence linked to Western diets and high fatty food intake.
• GERD Pathophysiology: Transient lower esophageal sphincter relaxation (TLESR) is the major mechanism of pathologic reflux; it is not related to swallowing and increases with gastric distention.
• GERD Barriers: Reflux can be caused by a defective anti-reflux barrier, which includes the lower esophageal sphincter (LES), the crural diaphragm, or the presence of a hiatal hernia.
• GERD Clearance Factors: Diminished esophageal clearance, affected by poor peristalsis, supine body position, or lack of saliva (xerostomia), contributes to the development of GERD.
• GERD External Triggers: High-fat diets, smoking (nicotine relaxes the LES), and medications like ACE inhibitors or Calcium Channel Blockers (CCBs) can exacerbate reflux.
• Natural History of GER: Infantile reflux peaks at 4 months of age and resolves in 88% of cases by 12 months; infants are often called "happy spitters" if they are active and feeding well despite reflux.
• Sandifer Syndrome: A unique clinical manifestation of GERD in infants characterized by neck contortions and arching (resembling opisthotonus) often associated with food refusal.
• Infantile GERD Symptoms: Manifestations include irritability, arching, choking, gagging, feeding aversion, and failure to thrive.
• Older Children GERD Symptoms: Presentations typically include heartburn, chest pain, abdominal pain, and sometimes difficult-to-treat asthma or chronic cough.
• GERD Diagnosis: GERD is primarily a clinical diagnosis based on history and physical examination; an empirical trial of PPI therapy for 2-4 weeks can confirm the diagnosis in older children and adults only.
• Diagnostic Imaging in Vomiting: Barium swallow can identify structural abnormalities such as achalasia (showing a "bird’s beak" appearance) but is not used to diagnose GERD itself.
• Nonpharmacologic Management of GERD: Strategies include avoiding overfeeding, thickening feeds, using hydrolyzed protein formula if allergy is suspected, and maintaining an upright position after feeds.
• Pharmacologic Management of GERD: Proton Pump Inhibitors (PPIs) like omeprazole are the only acid suppressants recommended for long-term treatment; H2RAs are not for chronic use, and prokinetics (e.g., domperidone) are generally discouraged.

Gastrointestinal Infections and Acute Gastroenteritis

Pathogenesis of Diarrhea

• Global Impact: Diarrhea is the top three cause of mortality in children under 5 years worldwide, particularly in low- to middle-income countries.
• Etiology of Gastroenteritis: Viruses are the most common etiologic group, with Rotavirus being the most common cause of severe diarrhea in children.
• Transmission: The primary route for GI infections is fecal-oral transmission via contaminated water, food, or person-to-person contact.
• Clinical Manifestation: Dehydration is the most common manifestation of acute gastroenteritis and is the priority for clinical assessment.
• Extraintestinal Complication - Reactive Arthritis: Patients may develop knee pain and joint inflammation 1-3 weeks after an infection with Salmonella or Shigella.
• Extraintestinal Complication - Guillain-Barre Syndrome: A neurological complication occurring a few weeks after a Campylobacter infection.
• Extraintestinal Complication - HUS: Hemolytic Uremic Syndrome presents with sudden onset renal failure following infection with Shigella dysenteriae 1 or E. coli O157:H7.
• Management - Rehydration: Rehydration therapy is the mainstay of treatment, using Oral Rehydration Salts (ORS) for mild cases and IV fluids for severe shock.
• Management - Zinc Supplementation: Zinc is recommended as a mainstay treatment to reduce the duration and severity of diarrhea episodes.
• Prevention: Strategies include Rotavirus vaccination, breastfeeding for up to 2 years, handwashing, and improved sanitation.

Functional Constipation and Encopresis

Rome IV Diagnostic Criteria (Must meet 2 or more for at least 1 month)

• Definition of Encopresis: The involuntary loss of stools into underwear after a child has reached the developmental age of 4 years.
• Timing of Constipation: Constitutional or functional constipation often starts around 6 months of age with the introduction of complementary feeding; onset <6 months suggests organic causes like Hirschsprung Disease.
• Alarm Signs of Hirschsprung Disease: 1) Onset in first month of life, 2) Meconium passage >48 hours, 3) Family history of HD, and 4) Ribbon stools.
• Neurologic Alarm Signs: The presence of a tuft of hair on the spine, sacral dimple, or gluteal cleft deviation may indicate a neurologic cause for constipation.
• Physical Exam Findings: Palpation often reveals a hard fecal mass in the left lower quadrant of the abdomen.
• Pharmacologic Management - Disimpaction: The first step of treatment is removing the stool ball via Glycerin suppositories (infants) or Phosphate enemas (older children); oral PEG can also be used for "slow" disimpaction.
• Pharmacologic Management - Maintenance: Once disimpacted, patients require weeks to months of maintenance laxatives (e.g., Lactulose or Polyethylene glycol) to prevent recurrence.
• Toilet Training Position: Proper positioning involves knees higher than hips, leaning forward with elbows on knees, and feet well-supported (not "frog" position).

Peptic Ulcer Disease (PUD)

Classification of Ulcers

• Secondary Ulcer Eponyms: Cushing Ulcer is associated with intracranial lesions; Curling Ulcer is associated with severe burn injuries.
• PUD Pathogenesis: Disease results from an imbalance where damaging factors (acid, pepsin, NSAIDs, H. pylori) outweigh defensive mechanisms (mucus, bicarbonate, prostaglandins).
• Clinical Presentation of PUD: The classic symptom is epigastric pain that is dull or aching and often alleviated by ingestion of food.
• PUD in Infants: Infants may present with non-specific symptoms such as irritability, vomiting, feeding difficulty, or hematemesis.
• Gold Standard Diagnosis: Upper Endoscopy (EGD) is the preferred diagnostic tool to visualize the ulcer, perform a biopsy, and screen for H. pylori.
• H. pylori Triple Therapy: Treatment consists of one month of a PPI combined with two antibiotics (e.g., Amoxicillin and Clarithromycin or Metronidazole) for 14 days.
• Surgical Indications: Surgery is reserved for complications such as uncontrollable bleeding, perforation, or obstruction.

Critical Comparisons and Differential Diagnoses

• GER vs. GERD: GER is a normal physiologic process ("happy spitter"), while GERD involves pathologic symptoms, complications, or failure to thrive.
• Vomiting vs. Reflux: Vomiting is a forceful passage of gastric contents; Reflux is an effortless passage.
• Classic PUD vs. GERD Pain: PUD pain is typically epigastric and relieved by food; GERD pain is often described as retrosternal/heartburn and may worsen after eating.
• Primary vs. Secondary PUD: Primary PUD is usually duodenal and H. pylori-related; secondary PUD is usually gastric and related to acute stress or drugs.
• Cushing vs. Curling Ulcer: Cushing ulcers are triggered by CNS/intracranial injury; Curling ulcers are triggered by severe burns.
• Non-inflammatory vs. Inflammatory Diarrhea: Non-inflammatory diarrhea is watery (toxin-mediated, no blood); inflammatory diarrhea is often bloody (dysentery) due to mucosal invasion.
• Functional Constipation vs. Hirschsprung Disease: Functional constipation usually starts at 6 months (dietary change) and has stools in the rectal vault; Hirschsprung presents at birth with delayed meconium and an empty rectum on exam.
• Encopresis vs. Diarrhea: Encopresis is the leakage of stool around a fecal impaction in a constipated child; diarrhea is an increase in stool frequency and liquidity without impaction.
• PPIs vs. H2RAs in GERD: PPIs (e.g., Omeprazole) are used for long-term management; H2RAs (e.g., Ranitidine) are not recommended for chronic GERD treatment.
• Projectile vs. Non-projectile Vomiting: Projectile vomiting suggests Increased ICP or Pyloric Stenosis; non-projectile vomiting is more common in GERD or Gastroenteritis.
• Bilious vs. Bloody Vomitus: Bilious vomiting (green) indicates obstruction distal to the ampulla of Vater; bloody vomiting (hematemesis) indicates gastritis, ulcers, or esophagitis.
• Achalasia vs. Pyloric Stenosis Imaging: Achalasia shows a "bird's beak" on barium swallow; Pyloric stenosis is typically diagnosed via ultrasound (thickened pylorus).
• Reactive Arthritis vs. Sepsis: Reactive arthritis is a post-infectious (1-3 weeks later) joint pain; sepsis is an acute, systemic inflammatory response during the active infection.
• Lactulose vs. Polyethylene Glycol (PEG): Both are osmotic laxatives used for maintenance in constipation; PEG is often used for both rapid disimpaction and maintenance.
• Sandifer Syndrome vs. Seizures: Sandifer syndrome involves arching and neck posturing temporally related to feeding (reflux-induced); seizures are generally not related to meals.

QA

text

Gastroesophageal Reflux (GER) and Disease (GERD)

1. What is the definition of Gastroesophageal Reflux (GER)? | Physiologic retrograde movement.
   Movement of gastric contents across the LES into the esophagus.
2. What is the definition of Gastroesophageal Reflux Disease (GERD)? | Pathologic reflux.
   Associated with troublesome symptoms or complications.
3. Contrast the complications of GER vs GERD. | GER: None; physiologic.
   GERD: Esophagitis, stricture, Barrett's, failure to thrive.
4. Contrast the effort of passage in GER vs GERD. | GER: Effortless (spitting up).
   GERD: Forceful passage or distress.
5. What is the most common esophageal disorder in children? | GERD.
6. Which dietary factors are linked to the increasing incidence of GERD? | Western diets.
   High fatty food intake.
7. What is the major mechanism of pathologic reflux in GERD? | Transient LES relaxation (TLESR).
8. Is Transient lower esophageal sphincter relaxation (TLESR) related to swallowing? | No.
9. What factor increases the frequency of Transient lower esophageal sphincter relaxation (TLESR)? | Gastric distention.
10. Name the components of the defective anti-reflux barrier in GERD. (3) | 1) LES
    2) Crural diaphragm
    3) Hiatal hernia.
11. How does diminished esophageal clearance contribute to GERD? | Prolongs acid contact.
    Affected by poor peristalsis or supine position.
12. How does xerostomia affect GERD? | Lack of saliva
    Decreases esophageal clearance.
13. Name three external triggers that exacerbate GERD. | 1) High-fat diets
    2) Smoking
    3) Medications.
14. How does nicotine from smoking affect the esophagus? | Relaxes the LES.
15. Which specific medication classes can exacerbate GERD? (2) | ACE inhibitors;
    Calcium Channel Blockers (CCBs).
16. At what age does infantile reflux peak? | 4 months of age.
17. By what age does GER resolve in 88% of cases? | 12 months.
18. What is the term for infants who are active and feeding well despite GER? | "Happy spitters".
19. What are the clinical signs of Sandifer Syndrome? (2) | Neck contortions and arching.
20. What does the arching in Sandifer Syndrome resemble? | Opisthotonus.
21. What behavioral symptom is often associated with Sandifer Syndrome? | Food refusal.
22. Name the manifestations of Infantile GERD. (5) | Irritability, arching, choking,
    feeding aversion, failure to thrive.
23. What are the typical symptoms of GERD in older children? (3) | Heartburn, chest pain, abdominal pain.
24. Which respiratory conditions may be associated with GERD in older children? | Asthma or chronic cough.
25. How is GERD primarily diagnosed? | Clinical diagnosis.
26. In which patients can an empirical trial of PPI therapy confirm GERD? | Older children and adults only.
27. What is the duration of an empirical PPI trial for GERD? | 2-4 weeks.
28. What is the role of a barium swallow in vomiting? | Identify structural abnormalities.
29. What is the classic barium swallow finding for achalasia? | "Bird’s beak" appearance.
30. Is a barium swallow used to diagnose GERD? | No.
31. List nonpharmacologic strategies for GERD management. (4) | Avoid overfeeding, thicken feeds,
    hydrolyzed formula, upright position.
32. Which acid suppressants are recommended for long-term GERD treatment? | Proton Pump Inhibitors (PPIs).
33. Are H2RAs recommended for chronic GERD use? | No.
34. What is the status of prokinetics (e.g., domperidone) in GERD management? | Generally discouraged.

Gastrointestinal Infections and Acute Gastroenteritis

35. Describe the mechanism of Noninflammatory diarrhea. | Enterotoxin production.
    Or villus destruction.
36. Are there WBCs or RBCs in the stool of Noninflammatory diarrhea? | No.
37. Name three pathogens that cause Noninflammatory diarrhea. | Rotavirus, Vibrio cholerae, ETEC.
38. Describe the mechanism of Inflammatory diarrhea. | Direct mucosal invasion.
    Or cytotoxin production.
39. What is the clinical stool appearance in Inflammatory diarrhea? | Bloody stools.
40. Name three pathogens that cause Inflammatory diarrhea. | Shigella, Salmonella, E. histolytica.
41. Describe the mechanism of Penetrating diarrhea. | Invasion beyond epithelium.
    Invasion beyond the intestinal epithelium.
42. Name three pathogens that cause Penetrating diarrhea. | Nontyphoidal Salmonella, Yersinia, Campylobacter.
43. What is the global impact of diarrhea in children under 5? | Top three cause of mortality.
44. What etiologic group is the most common cause of Gastroenteritis? | Viruses.
45. What is the most common cause of severe diarrhea in children? | Rotavirus.
46. What is the primary route of transmission for GI infections? | Fecal-oral transmission.
47. What is the most common manifestation of acute gastroenteritis? | Dehydration.
48. What is the priority for clinical assessment in Gastroenteritis? | Dehydration.
49. What extraintestinal complication involves knee pain 1-3 weeks after Salmonella or Shigella? | Reactive Arthritis.
50. What complication occurs weeks after a Campylobacter infection? | Guillain-Barre Syndrome.
51. What does Hemolytic Uremic Syndrome (HUS) present with? | Sudden onset renal failure.
52. Which pathogens are associated with Hemolytic Uremic Syndrome (HUS)? (2) | Shigella dysenteriae 1; E. coli O157:H7.
53. What is the mainstay of treatment for acute gastroenteritis? | Rehydration therapy.
54. What is used for rehydration in mild cases of gastroenteritis? | Oral Rehydration Salts (ORS).
55. What is the treatment for severe shock in gastroenteritis? | IV fluids.
56. Why is Zinc recommended in diarrhea management? | Reduce duration/severity.
57. List three strategies for prevention of GI infections. | 1) Rotavirus vaccination
    2) Breastfeeding (up to 2 yrs)
    3) Handwashing.

Functional Constipation and Encopresis

58. How many Rome IV criteria must be met for Functional Constipation? | 2 or more.
59. What is the frequency criterion for Functional Constipation? | ≤2 defecations per week.
60. What is the incontinence criterion for children ≥4 years? | At least 1 episode/week.
61. What is the posturing criterion for functional constipation? | Retentive posturing.
    History of volitional retention.
62. What is the mass criterion for functional constipation? | Large fecal mass in rectum.
63. What is the diameter criterion for functional constipation? | History of large diameter stools.
64. What is the definition of Encopresis? | Involuntary loss of stools.
65. What is the developmental age required for Encopresis diagnosis? | 4 years.
66. At what age does functional constipation often start? | 6 months of age.
67. What dietary change often triggers functional constipation? | Introduction of complementary feeding.
68. What is suggested if constipation onset is <6 months of age? | Organic causes.
    Ex: Hirschsprung Disease.
69. Name four alarm signs for Hirschsprung Disease. | 1) Onset month 1
    2) Meconium >48 hrs
    3) Family history
    4) Ribbon stools.
70. What is the meconium passage time alarm sign for Hirschsprung Disease? | >48 hours.
71. What do ribbon stools suggest? | Hirschsprung Disease.
72. Name three neurologic alarm signs for constipation. | 1) Tuft of hair on spine
    2) Sacral dimple
    3) Gluteal cleft deviation.
73. Where is a hard fecal mass usually palpated in functional constipation? | Left lower quadrant (LLQ).
74. What is the first step of Pharmacologic Management for constipation? | Disimpaction.
75. Which disimpaction method is used for infants? | Glycerin suppositories.
76. Which disimpaction method is used for older children? | Phosphate enemas.
77. What oral agent can be used for "slow" disimpaction? | Oral Polyethylene glycol (PEG).
78. What is the purpose of maintenance laxatives? | Prevent recurrence.
79. Name two laxatives used for maintenance. | Lactulose; Polyethylene glycol.
80. Describe the proper toilet training position. | Knees higher than hips.
    Leaning forward; feet supported.

Peptic Ulcer Disease (PUD)

81. What is the most common location for Primary PUD? | Duodenum (Duodenal bulb).
82. What is the primary cause of Primary PUD? | Helicobacter pylori.
83. What is the common location for Secondary PUD? | Stomach (Gastric).
84. Name causes of Secondary PUD. (4) | NSAIDs, Stress (sepsis),
    burns, intracranial lesions.
85. What is a Cushing Ulcer associated with? | Intracranial lesions.
86. What is a Curling Ulcer associated with? | Severe burn injuries.
87. What causes PUD Pathogenesis? | Imbalance of factors.
    Acid/pepsin vs mucus/bicarbonate/prostaglandins.
88. What is the classic symptom of Peptic Ulcer Disease (PUD)? | Epigastric pain.
89. How is PUD pain typically described? | Dull or aching.
90. What factor often alleviates PUD pain? | Ingestion of food.
91. Name symptoms of PUD in infants. | Irritability, vomiting,
    feeding difficulty, hematemesis.
92. What is the gold standard diagnosis for PUD? | Upper Endoscopy (EGD).
93. What can be performed during an Upper Endoscopy (EGD)? | Biopsy and H. pylori screening.
94. What is the PPI duration in H. pylori Triple Therapy? | One month.
95. What antibiotics are used in H. pylori Triple Therapy? (2) | Amoxicillin;
    Clarithromycin or Metronidazole.
96. How long is the course for antibiotics in Triple Therapy? | 14 days.
97. List three surgical indications for PUD. | 1) Uncontrollable bleeding
    2) Perforation
    3) Obstruction.

Critical Comparisons and Differential Diagnoses

98. Compare GER vs GERD. | GER: Normal ("happy spitter").
    GERD: Pathologic symptoms/complications.
99. Compare Vomiting vs Reflux. | Vomiting: Forceful passage.
    Reflux: Effortless passage.
100. Compare PUD vs GERD pain location. | PUD: Epigastric.
     GERD: Retrosternal/heartburn.
101. How is PUD vs GERD pain affected by eating? | PUD: Relieved by food.
     GERD: Worsens after eating.
102. Compare Cushing vs Curling Ulcer triggers. | Cushing: CNS injury.
     Curling: Severe burns.
103. Compare Non-inflammatory vs Inflammatory Diarrhea. | Non-inflammatory: Watery/toxin-mediated.
     Inflammatory: Bloody (dysentery).
104. Compare Functional Constipation vs Hirschsprung onset. | Functional: 6 months.
     Hirschsprung: At birth.
105. Compare Functional Constipation vs Hirschsprung rectal exam. | Functional: Stools in rectal vault.
     Hirschsprung: Empty rectum.
106. Compare Encopresis vs Diarrhea. | Encopresis: Leakage around fecal impaction.
     Diarrhea: Increased frequency/liquidity.
107. Compare PPI vs H2RA in GERD. | PPI: Long-term management.
     H2RA: Not for chronic use.
108. What causes Projectile vomiting? | Increased ICP or Pyloric Stenosis.
109. What causes Non-projectile vomiting? | GERD or Gastroenteritis.
110. What does Bilious vomiting (green) indicate? | Obstruction distal to ampulla of Vater.
111. What does Bloody vomiting (hematemesis) indicate? | Gastritis, ulcers, or esophagitis.
112. Compare Achalasia vs Pyloric Stenosis imaging. | Achalasia: Barium swallow ("bird's beak").
     Pyloric Stenosis: Ultrasound (thickened pylorus).
113. Compare Reactive Arthritis vs Sepsis joint timing. | Reactive: Post-infectious (1-3 weeks later).
     Sepsis: Acute systemic infection.
114. Compare Lactulose vs Polyethylene Glycol (PEG) use. | Both: Maintenance.
     PEG: Maintenance AND rapid disimpaction.
115. Compare Sandifer Syndrome vs Seizures. | Sandifer: related to feeding.
     Seizures: Not related to meals.

LE 2 - 6

Summary

text

Gastroesophageal Reflux (GER) and Disease (GERD)

Overview and Comparison

• Epidemiology of GERD: Gastroesophageal reflux disease is the most common esophageal disorder in children, with an increasing incidence linked to Western diets and high fatty food intake.
• GERD Pathophysiology: Transient lower esophageal sphincter relaxation (TLESR) is the major mechanism of pathologic reflux; it is not related to swallowing and increases with gastric distention.
• GERD Barriers: Reflux can be caused by a defective anti-reflux barrier, which includes the lower esophageal sphincter (LES), the crural diaphragm, or the presence of a hiatal hernia.
• GERD Clearance Factors: Diminished esophageal clearance, affected by poor peristalsis, supine body position, or lack of saliva (xerostomia), contributes to the development of GERD.
• GERD External Triggers: High-fat diets, smoking (nicotine relaxes the LES), and medications like ACE inhibitors or Calcium Channel Blockers (CCBs) can exacerbate reflux.
• Natural History of GER: Infantile reflux peaks at 4 months of age and resolves in 88% of cases by 12 months; infants are often called "happy spitters" if they are active and feeding well despite reflux.
• Sandifer Syndrome: A unique clinical manifestation of GERD in infants characterized by neck contortions and arching (resembling opisthotonus) often associated with food refusal.
• Infantile GERD Symptoms: Manifestations include irritability, arching, choking, gagging, feeding aversion, and failure to thrive.
• Older Children GERD Symptoms: Presentations typically include heartburn, chest pain, abdominal pain, and sometimes difficult-to-treat asthma or chronic cough.
• GERD Diagnosis: GERD is primarily a clinical diagnosis based on history and physical examination; an empirical trial of PPI therapy for 2-4 weeks can confirm the diagnosis in older children and adults only.
• Diagnostic Imaging in Vomiting: Barium swallow can identify structural abnormalities such as achalasia (showing a "bird’s beak" appearance) but is not used to diagnose GERD itself.
• Nonpharmacologic Management of GERD: Strategies include avoiding overfeeding, thickening feeds, using hydrolyzed protein formula if allergy is suspected, and maintaining an upright position after feeds.
• Pharmacologic Management of GERD: Proton Pump Inhibitors (PPIs) like omeprazole are the only acid suppressants recommended for long-term treatment; H2RAs are not for chronic use, and prokinetics (e.g., domperidone) are generally discouraged.

Gastrointestinal Infections and Acute Gastroenteritis

Pathogenesis of Diarrhea

• Global Impact: Diarrhea is the top three cause of mortality in children under 5 years worldwide, particularly in low- to middle-income countries.
• Etiology of Gastroenteritis: Viruses are the most common etiologic group, with Rotavirus being the most common cause of severe diarrhea in children.
• Transmission: The primary route for GI infections is fecal-oral transmission via contaminated water, food, or person-to-person contact.
• Clinical Manifestation: Dehydration is the most common manifestation of acute gastroenteritis and is the priority for clinical assessment.
• Extraintestinal Complication - Reactive Arthritis: Patients may develop knee pain and joint inflammation 1-3 weeks after an infection with Salmonella or Shigella.
• Extraintestinal Complication - Guillain-Barre Syndrome: A neurological complication occurring a few weeks after a Campylobacter infection.
• Extraintestinal Complication - HUS: Hemolytic Uremic Syndrome presents with sudden onset renal failure following infection with Shigella dysenteriae 1 or E. coli O157:H7.
• Management - Rehydration: Rehydration therapy is the mainstay of treatment, using Oral Rehydration Salts (ORS) for mild cases and IV fluids for severe shock.
• Management - Zinc Supplementation: Zinc is recommended as a mainstay treatment to reduce the duration and severity of diarrhea episodes.
• Prevention: Strategies include Rotavirus vaccination, breastfeeding for up to 2 years, handwashing, and improved sanitation.

Functional Constipation and Encopresis

Rome IV Diagnostic Criteria (Must meet 2 or more for at least 1 month)

• Definition of Encopresis: The involuntary loss of stools into underwear after a child has reached the developmental age of 4 years.
• Timing of Constipation: Constitutional or functional constipation often starts around 6 months of age with the introduction of complementary feeding; onset <6 months suggests organic causes like Hirschsprung Disease.
• Alarm Signs of Hirschsprung Disease: 1) Onset in first month of life, 2) Meconium passage >48 hours, 3) Family history of HD, and 4) Ribbon stools.
• Neurologic Alarm Signs: The presence of a tuft of hair on the spine, sacral dimple, or gluteal cleft deviation may indicate a neurologic cause for constipation.
• Physical Exam Findings: Palpation often reveals a hard fecal mass in the left lower quadrant of the abdomen.
• Pharmacologic Management - Disimpaction: The first step of treatment is removing the stool ball via Glycerin suppositories (infants) or Phosphate enemas (older children); oral PEG can also be used for "slow" disimpaction.
• Pharmacologic Management - Maintenance: Once disimpacted, patients require weeks to months of maintenance laxatives (e.g., Lactulose or Polyethylene glycol) to prevent recurrence.
• Toilet Training Position: Proper positioning involves knees higher than hips, leaning forward with elbows on knees, and feet well-supported (not "frog" position).

Peptic Ulcer Disease (PUD)

Classification of Ulcers

• Secondary Ulcer Eponyms: Cushing Ulcer is associated with intracranial lesions; Curling Ulcer is associated with severe burn injuries.
• PUD Pathogenesis: Disease results from an imbalance where damaging factors (acid, pepsin, NSAIDs, H. pylori) outweigh defensive mechanisms (mucus, bicarbonate, prostaglandins).
• Clinical Presentation of PUD: The classic symptom is epigastric pain that is dull or aching and often alleviated by ingestion of food.
• PUD in Infants: Infants may present with non-specific symptoms such as irritability, vomiting, feeding difficulty, or hematemesis.
• Gold Standard Diagnosis: Upper Endoscopy (EGD) is the preferred diagnostic tool to visualize the ulcer, perform a biopsy, and screen for H. pylori.
• H. pylori Triple Therapy: Treatment consists of one month of a PPI combined with two antibiotics (e.g., Amoxicillin and Clarithromycin or Metronidazole) for 14 days.
• Surgical Indications: Surgery is reserved for complications such as uncontrollable bleeding, perforation, or obstruction.

Critical Comparisons and Differential Diagnoses

• GER vs. GERD: GER is a normal physiologic process ("happy spitter"), while GERD involves pathologic symptoms, complications, or failure to thrive.
• Vomiting vs. Reflux: Vomiting is a forceful passage of gastric contents; Reflux is an effortless passage.
• Classic PUD vs. GERD Pain: PUD pain is typically epigastric and relieved by food; GERD pain is often described as retrosternal/heartburn and may worsen after eating.
• Primary vs. Secondary PUD: Primary PUD is usually duodenal and H. pylori-related; secondary PUD is usually gastric and related to acute stress or drugs.
• Cushing vs. Curling Ulcer: Cushing ulcers are triggered by CNS/intracranial injury; Curling ulcers are triggered by severe burns.
• Non-inflammatory vs. Inflammatory Diarrhea: Non-inflammatory diarrhea is watery (toxin-mediated, no blood); inflammatory diarrhea is often bloody (dysentery) due to mucosal invasion.
• Functional Constipation vs. Hirschsprung Disease: Functional constipation usually starts at 6 months (dietary change) and has stools in the rectal vault; Hirschsprung presents at birth with delayed meconium and an empty rectum on exam.
• Encopresis vs. Diarrhea: Encopresis is the leakage of stool around a fecal impaction in a constipated child; diarrhea is an increase in stool frequency and liquidity without impaction.
• PPIs vs. H2RAs in GERD: PPIs (e.g., Omeprazole) are used for long-term management; H2RAs (e.g., Ranitidine) are not recommended for chronic GERD treatment.
• Projectile vs. Non-projectile Vomiting: Projectile vomiting suggests Increased ICP or Pyloric Stenosis; non-projectile vomiting is more common in GERD or Gastroenteritis.
• Bilious vs. Bloody Vomitus: Bilious vomiting (green) indicates obstruction distal to the ampulla of Vater; bloody vomiting (hematemesis) indicates gastritis, ulcers, or esophagitis.
• Achalasia vs. Pyloric Stenosis Imaging: Achalasia shows a "bird's beak" on barium swallow; Pyloric stenosis is typically diagnosed via ultrasound (thickened pylorus).
• Reactive Arthritis vs. Sepsis: Reactive arthritis is a post-infectious (1-3 weeks later) joint pain; sepsis is an acute, systemic inflammatory response during the active infection.
• Lactulose vs. Polyethylene Glycol (PEG): Both are osmotic laxatives used for maintenance in constipation; PEG is often used for both rapid disimpaction and maintenance.
• Sandifer Syndrome vs. Seizures: Sandifer syndrome involves arching and neck posturing temporally related to feeding (reflux-induced); seizures are generally not related to meals.

QA

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Gastroesophageal Reflux (GER) and Disease (GERD)

1. What is the definition of Gastroesophageal Reflux (GER)? | Physiologic retrograde movement.
   Movement of gastric contents across the LES into the esophagus.
2. What is the definition of Gastroesophageal Reflux Disease (GERD)? | Pathologic reflux.
   Associated with troublesome symptoms or complications.
3. Contrast the complications of GER vs GERD. | GER: None; physiologic.
   GERD: Esophagitis, stricture, Barrett's, failure to thrive.
4. Contrast the effort of passage in GER vs GERD. | GER: Effortless (spitting up).
   GERD: Forceful passage or distress.
5. What is the most common esophageal disorder in children? | GERD.
6. Which dietary factors are linked to the increasing incidence of GERD? | Western diets.
   High fatty food intake.
7. What is the major mechanism of pathologic reflux in GERD? | Transient LES relaxation (TLESR).
8. Is Transient lower esophageal sphincter relaxation (TLESR) related to swallowing? | No.
9. What factor increases the frequency of Transient lower esophageal sphincter relaxation (TLESR)? | Gastric distention.
10. Name the components of the defective anti-reflux barrier in GERD. (3) | 1) LES
    2) Crural diaphragm
    3) Hiatal hernia.
11. How does diminished esophageal clearance contribute to GERD? | Prolongs acid contact.
    Affected by poor peristalsis or supine position.
12. How does xerostomia affect GERD? | Lack of saliva
    Decreases esophageal clearance.
13. Name three external triggers that exacerbate GERD. | 1) High-fat diets
    2) Smoking
    3) Medications.
14. How does nicotine from smoking affect the esophagus? | Relaxes the LES.
15. Which specific medication classes can exacerbate GERD? (2) | ACE inhibitors;
    Calcium Channel Blockers (CCBs).
16. At what age does infantile reflux peak? | 4 months of age.
17. By what age does GER resolve in 88% of cases? | 12 months.
18. What is the term for infants who are active and feeding well despite GER? | "Happy spitters".
19. What are the clinical signs of Sandifer Syndrome? (2) | Neck contortions and arching.
20. What does the arching in Sandifer Syndrome resemble? | Opisthotonus.
21. What behavioral symptom is often associated with Sandifer Syndrome? | Food refusal.
22. Name the manifestations of Infantile GERD. (5) | Irritability, arching, choking,
    feeding aversion, failure to thrive.
23. What are the typical symptoms of GERD in older children? (3) | Heartburn, chest pain, abdominal pain.
24. Which respiratory conditions may be associated with GERD in older children? | Asthma or chronic cough.
25. How is GERD primarily diagnosed? | Clinical diagnosis.
26. In which patients can an empirical trial of PPI therapy confirm GERD? | Older children and adults only.
27. What is the duration of an empirical PPI trial for GERD? | 2-4 weeks.
28. What is the role of a barium swallow in vomiting? | Identify structural abnormalities.
29. What is the classic barium swallow finding for achalasia? | "Bird’s beak" appearance.
30. Is a barium swallow used to diagnose GERD? | No.
31. List nonpharmacologic strategies for GERD management. (4) | Avoid overfeeding, thicken feeds,
    hydrolyzed formula, upright position.
32. Which acid suppressants are recommended for long-term GERD treatment? | Proton Pump Inhibitors (PPIs).
33. Are H2RAs recommended for chronic GERD use? | No.
34. What is the status of prokinetics (e.g., domperidone) in GERD management? | Generally discouraged.

Gastrointestinal Infections and Acute Gastroenteritis

35. Describe the mechanism of Noninflammatory diarrhea. | Enterotoxin production.
    Or villus destruction.
36. Are there WBCs or RBCs in the stool of Noninflammatory diarrhea? | No.
37. Name three pathogens that cause Noninflammatory diarrhea. | Rotavirus, Vibrio cholerae, ETEC.
38. Describe the mechanism of Inflammatory diarrhea. | Direct mucosal invasion.
    Or cytotoxin production.
39. What is the clinical stool appearance in Inflammatory diarrhea? | Bloody stools.
40. Name three pathogens that cause Inflammatory diarrhea. | Shigella, Salmonella, E. histolytica.
41. Describe the mechanism of Penetrating diarrhea. | Invasion beyond epithelium.
    Invasion beyond the intestinal epithelium.
42. Name three pathogens that cause Penetrating diarrhea. | Nontyphoidal Salmonella, Yersinia, Campylobacter.
43. What is the global impact of diarrhea in children under 5? | Top three cause of mortality.
44. What etiologic group is the most common cause of Gastroenteritis? | Viruses.
45. What is the most common cause of severe diarrhea in children? | Rotavirus.
46. What is the primary route of transmission for GI infections? | Fecal-oral transmission.
47. What is the most common manifestation of acute gastroenteritis? | Dehydration.
48. What is the priority for clinical assessment in Gastroenteritis? | Dehydration.
49. What extraintestinal complication involves knee pain 1-3 weeks after Salmonella or Shigella? | Reactive Arthritis.
50. What complication occurs weeks after a Campylobacter infection? | Guillain-Barre Syndrome.
51. What does Hemolytic Uremic Syndrome (HUS) present with? | Sudden onset renal failure.
52. Which pathogens are associated with Hemolytic Uremic Syndrome (HUS)? (2) | Shigella dysenteriae 1; E. coli O157:H7.
53. What is the mainstay of treatment for acute gastroenteritis? | Rehydration therapy.
54. What is used for rehydration in mild cases of gastroenteritis? | Oral Rehydration Salts (ORS).
55. What is the treatment for severe shock in gastroenteritis? | IV fluids.
56. Why is Zinc recommended in diarrhea management? | Reduce duration/severity.
57. List three strategies for prevention of GI infections. | 1) Rotavirus vaccination
    2) Breastfeeding (up to 2 yrs)
    3) Handwashing.

Functional Constipation and Encopresis

58. How many Rome IV criteria must be met for Functional Constipation? | 2 or more.
59. What is the frequency criterion for Functional Constipation? | ≤2 defecations per week.
60. What is the incontinence criterion for children ≥4 years? | At least 1 episode/week.
61. What is the posturing criterion for functional constipation? | Retentive posturing.
    History of volitional retention.
62. What is the mass criterion for functional constipation? | Large fecal mass in rectum.
63. What is the diameter criterion for functional constipation? | History of large diameter stools.
64. What is the definition of Encopresis? | Involuntary loss of stools.
65. What is the developmental age required for Encopresis diagnosis? | 4 years.
66. At what age does functional constipation often start? | 6 months of age.
67. What dietary change often triggers functional constipation? | Introduction of complementary feeding.
68. What is suggested if constipation onset is &lt6 months of age? | Organic causes.
    Ex: Hirschsprung Disease.
69. Name four alarm signs for Hirschsprung Disease. | 1) Onset month 1
    2) Meconium >48 hrs
    3) Family history
    4) Ribbon stools.
70. What is the meconium passage time alarm sign for Hirschsprung Disease? | >48 hours.
71. What do ribbon stools suggest? | Hirschsprung Disease.
72. Name three neurologic alarm signs for constipation. | 1) Tuft of hair on spine
    2) Sacral dimple
    3) Gluteal cleft deviation.
73. Where is a hard fecal mass usually palpated in functional constipation? | Left lower quadrant (LLQ).
74. What is the first step of Pharmacologic Management for constipation? | Disimpaction.
75. Which disimpaction method is used for infants? | Glycerin suppositories.
76. Which disimpaction method is used for older children? | Phosphate enemas.
77. What oral agent can be used for "slow" disimpaction? | Oral Polyethylene glycol (PEG).
78. What is the purpose of maintenance laxatives? | Prevent recurrence.
79. Name two laxatives used for maintenance. | Lactulose; Polyethylene glycol.
80. Describe the proper toilet training position. | Knees higher than hips.
    Leaning forward; feet supported.

Peptic Ulcer Disease (PUD)

81. What is the most common location for Primary PUD? | Duodenum (Duodenal bulb).
82. What is the primary cause of Primary PUD? | Helicobacter pylori.
83. What is the common location for Secondary PUD? | Stomach (Gastric).
84. Name causes of Secondary PUD. (4) | NSAIDs, Stress (sepsis),
    burns, intracranial lesions.
85. What is a Cushing Ulcer associated with? | Intracranial lesions.
86. What is a Curling Ulcer associated with? | Severe burn injuries.
87. What causes PUD Pathogenesis? | Imbalance of factors.
    Acid/pepsin vs mucus/bicarbonate/prostaglandins.
88. What is the classic symptom of Peptic Ulcer Disease (PUD)? | Epigastric pain.
89. How is PUD pain typically described? | Dull or aching.
90. What factor often alleviates PUD pain? | Ingestion of food.
91. Name symptoms of PUD in infants. | Irritability, vomiting,
    feeding difficulty, hematemesis.
92. What is the gold standard diagnosis for PUD? | Upper Endoscopy (EGD).
93. What can be performed during an Upper Endoscopy (EGD)? | Biopsy and H. pylori screening.
94. What is the PPI duration in H. pylori Triple Therapy? | One month.
95. What antibiotics are used in H. pylori Triple Therapy? (2) | Amoxicillin;
    Clarithromycin or Metronidazole.
96. How long is the course for antibiotics in Triple Therapy? | 14 days.
97. List three surgical indications for PUD. | 1) Uncontrollable bleeding
    2) Perforation
    3) Obstruction.

Critical Comparisons and Differential Diagnoses

98. Compare GER vs GERD. | GER: Normal ("happy spitter").
    GERD: Pathologic symptoms/complications.
99. Compare Vomiting vs Reflux. | Vomiting: Forceful passage.
    Reflux: Effortless passage.
100. Compare PUD vs GERD pain location. | PUD: Epigastric.
     GERD: Retrosternal/heartburn.
101. How is PUD vs GERD pain affected by eating? | PUD: Relieved by food.
     GERD: Worsens after eating.
102. Compare Cushing vs Curling Ulcer triggers. | Cushing: CNS injury.
     Curling: Severe burns.
103. Compare Non-inflammatory vs Inflammatory Diarrhea. | Non-inflammatory: Watery/toxin-mediated.
     Inflammatory: Bloody (dysentery).
104. Compare Functional Constipation vs Hirschsprung onset. | Functional: 6 months.
     Hirschsprung: At birth.
105. Compare Functional Constipation vs Hirschsprung rectal exam. | Functional: Stools in rectal vault.
     Hirschsprung: Empty rectum.
106. Compare Encopresis vs Diarrhea. | Encopresis: Leakage around fecal impaction.
     Diarrhea: Increased frequency/liquidity.
107. Compare PPI vs H2RA in GERD. | PPI: Long-term management.
     H2RA: Not for chronic use.
108. What causes Projectile vomiting? | Increased ICP or Pyloric Stenosis.
109. What causes Non-projectile vomiting? | GERD or Gastroenteritis.
110. What does Bilious vomiting (green) indicate? | Obstruction distal to ampulla of Vater.
111. What does Bloody vomiting (hematemesis) indicate? | Gastritis, ulcers, or esophagitis.
112. Compare Achalasia vs Pyloric Stenosis imaging. | Achalasia: Barium swallow ("bird's beak").
     Pyloric Stenosis: Ultrasound (thickened pylorus).
113. Compare Reactive Arthritis vs Sepsis joint timing. | Reactive: Post-infectious (1-3 weeks later).
     Sepsis: Acute systemic infection.
114. Compare Lactulose vs Polyethylene Glycol (PEG) use. | Both: Maintenance.
     PEG: Maintenance AND rapid disimpaction.
115. Compare Sandifer Syndrome vs Seizures. | Sandifer: related to feeding.
     Seizures: Not related to meals.

7 - Intestinal Obstruction

Summary

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Intestinal Obstruction: General Principles

Functional Obstruction: Ileus

• Ileus is defined as the failure of intestinal peristalsis (paralytic/adynamic) without evidence of mechanical obstruction.
• Common triggers for Ileus include abdominal surgery (usually resolves within 72 hours), infections (AGE, pneumonia, peritonitis), and metabolic abnormalities like hypokalemia, hypercalcemia, and acidosis.
• Medications that cause Ileus include opiates, vincristine, and antimotility agents like loperamide.
• The clinical presentation of Ileus involves abdominal distention, nausea, vomiting, a tympanitic abdomen, and minimal or absent bowel sounds.
• Radiographic diagnosis of Ileus shows air-fluid levels without progressive bowel distention; barium enema reveals delayed movement through the lumen.
• Management of Ileus focuses on correcting underlying abnormalities, nasogastric decompression, fluid replacement, and mitigating iatrogenic causes (e.g., stopping offending drugs).

Mechanical Obstruction: Intussusception

• Intussusception is the invagination of one segment of intestine (intussusceptum) into an adjacent segment (intussuscipiens).
• Intussusception is the most common cause of intestinal obstruction in children between 5 months and 3 years of age.
• Intussusception is the most common abdominal emergency in children under 2 years old, with a 3:1 male-to-female ratio.
• The most common anatomic type of Intussusception is ileocolic, followed by cecocolic and ileoileal.
• While 90% of cases are idiopathic (often linked to hypertrophied Peyer's patches), lead points like Meckel diverticulum, polyps, or lymphoma are common in children over 2 years old.
• The typical presentation of Intussusception is a previously well child with sudden, paroxysmal colicky pain who is comfortable between episodes.
• The classic triad of Intussusception (occurring in <30% of cases) includes abdominal pain, a sausage-shaped mass, and "currant jelly" stools (blood + mucus).
• Physical examination of Intussusception may reveal a slightly tender, sausage-shaped mass in the right upper abdomen.
• On Ultrasound, Intussusception is diagnosed by the "Target sign" or "Pseudo-kidney sign"; Barium enema shows the "Coiled spring sign."
• Conservative treatment for Intussusception involves radiologic hydrostatic reduction (fluoroscopic or ultrasound-guided).
• Surgical intervention for Intussusception is indicated for shock, suspected bowel necrosis/perf, peritonitis, or multiple recurrences.

Inflammatory Bowel Disease (IBD)

• IBD pathogenesis involves genetic predisposition (e.g., NOD2 gene in CD), dysbiosis (microbiota imbalance), and environmental triggers like the Western diet.
• Diagnosis of IBD utilizes Fecal calprotectin as a marker of inflammation and colonoscopy with biopsy for confirmation.
• Pharmacological treatment of IBD includes Aminosalicylates (first-line for mild UC), Corticosteroids (remission induction), and Biologics (Anti-TNF like Infliximab).
• Exclusive Enteral Nutrition (EEN) is a primary therapy for pediatric Crohn's Disease.
• Long-term monitoring for IBD involves growth tracking, bone density (osteopenia risk), and cancer screening for chronic UC.

Disorders of Malabsorption

• Celiac Disease is an immune-mediated disorder elicited by gluten (found in wheat, rye, and barley) in genetically predisposed individuals (HLA-DQ2.5/DQ8).
• Repeated rotavirus infections are associated with an increased risk of developing Celiac Disease.
• Iron deficiency anemia is the most common extraintestinal manifestation of Celiac Disease.
• Diagnostic serology for Celiac Disease includes anti-TG2 IgA (first line) and anti-endomysial antibodies.
• Small bowel biopsy in Celiac Disease reveals villous atrophy, crypt hyperplasia, and increased intraepithelial lymphocytes.
• Treatment for Celiac Disease requires a lifelong, strict gluten-free diet and correction of micronutrient deficiencies (Iron, Zinc, Vit D).
• Postinfectious Diarrhea in toddlers is often caused by secondary lactase deficiency or food protein allergy following an acute GI infection.
• Bacterial Overgrowth (SIBO) involves colonization of the small intestine, leading to steatorrhea (from bile salt deconjugation) and Vitamin B12 deficiency; treated with Metronidazole.
• Short Bowel Syndrome results from malabsorption secondary to the loss of >50% of the small bowel.
• Lactase Deficiency types include primary (physiologic decline common in 40% of Asians) and secondary lactose intolerance (transient damage post-infection/malnutrition).
• Diagnosis of Lactase Deficiency is usually made via a dietary elimination trial or an H2 breath test.

Critical Comparisons and High-Yield Distinctions

1. Functional (Ileus) vs Mechanical Obstruction: Ileus presents with absent/minimal bowel sounds and is non-mechanical; Mechanical presents with hyperactive sounds initially and a physical blockage.
2. Upper vs Lower GI Obstruction: Upper GI presents with bilious vomiting and low distention; Lower GI presents with feculent vomiting and significant distention.
3. Crohn's vs Ulcerative Colitis Distribution: Crohn's is anywhere (skip lesions); UC is rectum/colon only (continuous).
4. Crohn's vs Ulcerative Colitis Depth: Crohn's is transmural (all layers); UC is mucosal only.
5. Growth Failure: Highly common in pediatric Crohn's; rare in Ulcerative Colitis.
6. Bleeding Profile: Gross rectal bleeding is the hallmark of UC; bleeding in Crohn's is less consistent but perianal disease (fistulas) is prominent.
7. Intussusception Triad: Sausage mass, paroxysmal pain, and currant jelly stools.
8. Imaging Signs: Target sign (Intussusception U/S or CT obstruction); Coiled spring (Intussusception Barium); Bird's beak (CT obstruction).
9. Meconium Passage: Failure to pass meconium within 24-48 hours is an alarm sign for Hirschsprung or neonatal obstruction.
10. Celiac Pathology: Characterized by villous atrophy; whereas Lactase deficiency is an enzymatic/transport defect without necessarily having atrophy (except in secondary cases).
11. Nutrient Deficiencies: Iron deficiency is the top sign in Celiac; Vitamin B12 deficiency is a hallmark of Bacterial Overgrowth.
12. Age of Onset: Intussusception peaks at 5 months to 3 years; IBD peaks in late adolescence.
13. Strangulating vs Simple Obstruction: Strangulating presents with fever, acidosis, and leukocytosis; simple obstruction presents mainly with mechanical symptoms.
14. Celiac Serology: Anti-TG2 IgA is the first-line test; total IgA must be checked to ensure no IgA deficiency is masking results.
15. Lactose Intolerance Diagnosis: A clinical dietary elimination trial is often preferred over the more complex H2 breath test.

QA

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Intestinal Obstruction: General Principles

1. What are the 2 classifications of Intestinal Obstruction by mechanism? | Functional and Mechanical

2. Define Functional Obstruction mechanisms. | Myopathic or neuropathic

3. Define Mechanical Obstruction mechanisms. | Physical intraluminal or extraintestinal

4. What are the 2 classifications of Intestinal Obstruction by extent? | Partial and Complete

5. Which Obstruction extent allows the passage of liquid or gas? | Partial

6. Which Obstruction extent allows nothing to pass? | Complete

7. Compare Upper GI vs Lower GI Localization: Vomiting type. | Upper: Bilious
   Lower: Feculent

8. Compare Upper GI vs Lower GI Localization: Distention. | Upper: Minimal
   Lower: Abdominal distention

9. What are the 2 Obstruction types based on blood flow? | Simple and Strangulating

10. Define Simple Obstruction. | Partial/complete without ischemia

11. Define Strangulating Obstruction. | Compromised blood flow

12. Neonatal Presentation: What maternal history suggests Obstruction? | Maternal polyhydramnios

13. Neonatal Presentation: Failure to pass meconium occurs within what timeframe? | 24-48 hours

14. Neonatal Presentation: What color/type of stool is concerning? | "Currant jelly" stools

15. Intestinal Obstruction: Child/Adolescent Presentation (5). | 1) Colicky abdominal pain
    2) Distention
    3) Nausea
    4) Vomiting
    5) Obstipation

16. Physical Exam: What bowel sounds are found in Mechanical Obstruction? | Hyperactive bowel sounds

17. Physical Exam: What findings suggest Strangulating Obstruction? | Absent bowel sounds and painful mass

18. Radiographic Signs: What is seen on Plain X-ray for Obstruction? (3) | 1) Distended loops
    2) Air-fluid levels
    3) Paucity of colonic air

19. CT Scan Findings: What does the "Target sign" indicate? | Bowel wall thickening

20. CT Scan Findings: What is the term for "air in the bowel wall"? | Pneumatosis intestinalis

21. CT Scan Findings: What finding indicates gas in the veins? | Portal venous gas

22. CT Scan Findings: What does the beak sign indicate? | Distal narrowing

23. Intestinal Obstruction Management Priorities (5). | 1) Bowel decompression
    2) Fluid resuscitation
    3) Monitoring electrolytes
    4) Conservative trial
    5) Early surgery

24. Management: What is the first priority for bowel decompression? | NGT or OGT

25. Management: When is a conservative trial appropriate? | Partial obstruction

26. Management: When is early surgery indicated? (2) | 1) Complete obstruction
    2) Malrotation

Functional Obstruction: Ileus

27. Define Ileus. | Failure of intestinal peristalsis

28. Is Ileus a mechanical or non-mechanical obstruction? | Non-mechanical (paralytic/adynamic)

29. Ileus Triggers: Abdominal surgery usually resolves within how many hours? | 72 hours

30. Ileus Triggers: List 3 infection types. | 1) AGE
    2) Pneumonia
    3) Peritonitis

31. Ileus Triggers: What metabolic abnormalities are causes? (3) | 1) Hypokalemia
    2) Hypercalcemia
    3) Acidosis

32. What medication types cause Ileus? (3) | 1) Opiates
    2) Vincristine
    3) Antimotility agents

33. Which specific antimotility agent is a known cause of Ileus? | Loperamide

34. Clinical Presentation of Ileus (5). | 1) Abdominal distention
    2) Nausea
    3) Vomiting
    4) Tympanitic abdomen
    5) Minimal/absent bowel sounds

35. Radiographic diagnosis of Ileus: Plain X-ray finding. | Air-fluid levels without distention

36. Radiographic diagnosis of Ileus: Barium enema finding. | Delayed movement through lumen

37. Management of Ileus focuses on what primary step? | Correcting underlying abnormalities

38. Management of Ileus: How is bowel pressure relieved? | Nasogastric decompression

39. Management of Ileus: What prevents iatrogenic progression? | Stopping offending drugs

Mechanical Obstruction: Intussusception

40. Define Intussusception. | Invagination of one intestine segment

41. In Intussusception, what is the name of the segment that invaginates? | Intussusceptum

42. In Intussusception, what is the name of the receiving segment? | Intussuscipiens

43. What is the peak age range for Intussusception? | 5 months to 3 years

44. Intussusception is the most common abdominal emergency in children under what age? | 2 years old

45. What is the male-to-female ratio in Intussusception? | 3:1 ratio

46. What is the most common anatomic type of Intussusception? | Ileocolic

47. Name 2 less common anatomic types of Intussusception. | Cecocolic and ileoileal

48. What percentage of Intussusception cases are idiopathic? | 90%

49. What physiologic finding is often linked to idiopathic Intussusception? | Hypertrophied Peyer's patches

50. Lead points in Intussusception are common in children over what age? | 2 years old

51. Name 3 potential "lead points" for Intussusception. | 1) Meckel diverticulum
    2) Polyps
    3) Lymphoma

52. Describe the typical pain in Intussusception. | Sudden, paroxysmal colicky pain

53. How does a child with Intussusception act between pain episodes? | Comfortable/well

54. The classic triad of Intussusception includes (3). | 1) Abdominal pain
    2) Sausage-shaped mass
    3) "Currant jelly" stools

55. What is the consistency of "currant jelly" stools? | Blood + mucus

56. Physical examination of Intussusception: Mass description and location. | Sausage-shaped mass in RUQ

57. Ultrasound signs for Intussusception (2). | "Target sign" or "Pseudo-kidney sign"

58. Barium enema sign for Intussusception. | "Coiled spring sign"

59. What is the primary conservative treatment for Intussusception? | Radiologic hydrostatic reduction

60. Name 2 methods of hydrostatic reduction for Intussusception. | Fluoroscopic or ultrasound-guided

61. List 4 indications for surgical intervention in Intussusception. | 1) Shock
    2) Bowel necrosis/perf
    3) Peritonitis
    4) Multiple recurrences

Inflammatory Bowel Disease (IBD)

62. IBD Distribution: Compare Crohn's Disease vs Ulcerative Colitis. | Crohn's: Mouth to anus (Skip lesions)
    UC: Colon and rectum (Continuous)

63. IBD Inflammation Depth: Compare Crohn's Disease vs Ulcerative Colitis. | Crohn's: Transmural
    UC: Mucosal

64. GI Symptoms: Which IBD type presents with RLQ mass and perianal lesions? | Crohn's Disease

65. GI Symptoms: What is the hallmark symptom of Ulcerative Colitis? | Rectal bleeding (with mucus)

66. Growth Failure: Is it more common in Crohn's Disease or Ulcerative Colitis? | Crohn's Disease

67. IBD Histology: Which disease features Noncaseating granulomas? | Crohn's Disease

68. IBD Histology: What is found in Ulcerative Colitis? | Crypt distortion and abscesses

69. Extraintestinal: What skin condition is specific to Ulcerative Colitis in this text? | Pyoderma gangrenosum

70. Extraintestinal: Which IBD is linked to Sclerosing cholangitis? | Ulcerative Colitis

71. Pathogenesis of IBD: What gene is associated with Crohn's Disease? | NOD2 gene

72. Pathogenesis of IBD: Define "dysbiosis". | Microbiota imbalance

73. Diagnosis of IBD: What stool marker measures inflammation? | Fecal calprotectin

74. Diagnosis of IBD: What is required for confirmation? | Colonoscopy with biopsy

75. Pharmacological treatment: What is the first-line for mild Ulcerative Colitis? | Aminosalicylates

76. Pharmacological treatment: What is used for remission induction in IBD? | Corticosteroids

77. Name a common Anti-TNF Biologic used in IBD. | Infliximab

78. What is the primary dietary therapy for pediatric Crohn's Disease? | Exclusive Enteral Nutrition (EEN)

79. Long-term monitoring for IBD (3). | 1) Growth
    2) Bone density
    3) Cancer screening

80. Why is bone density monitored in IBD? | Osteopenia risk

81. Which IBD chronic condition requires cancer screening? | Chronic UC

Disorders of Malabsorption

82. Define Celiac Disease. | Immune-mediated disorder elicited by gluten

83. What grains contain gluten? (3) | Wheat, rye, and barley

84. What genetic markers are linked to Celiac Disease? | HLA-DQ2.5/DQ8

85. Which infection is associated with an increased risk of Celiac Disease? | Repeated rotavirus infections

86. What is the most common extraintestinal manifestation of Celiac Disease? | Iron deficiency anemia

87. What is the first-line serology for Celiac Disease? | anti-TG2 IgA

88. Serology: Name another antibody tested in Celiac Disease. | Anti-endomysial antibodies

89. Small bowel biopsy findings in Celiac Disease (3). | 1) Villous atrophy
    2) Crypt hyperplasia
    3) Increased lymphocytes

90. Treatment for Celiac Disease (2). | 1) Gluten-free diet
    2) Nutrient correction

91. Which micronutrients often require correction in Celiac? (3) | Iron, Zinc, Vitamin D

92. What causes Postinfectious Diarrhea in toddlers? | Secondary lactase deficiency or allergy

93. Define Bacterial Overgrowth (SIBO) mechanism. | Colonization of small intestine

94. Bacterial Overgrowth leads to what stool finding? | Steatorrhea

95. Why does SIBO cause steatorrhea? | Bile salt deconjugation

96. Which vitamin is deficient in Bacterial Overgrowth? | Vitamin B12

97. What is the treatment for Bacterial Overgrowth? | Metronidazole

98. Define Short Bowel Syndrome. | Loss of >50% of small bowel

99. Lactase Deficiency: Describe "Primary" deficiency. | Physiologic decline (common in Asians)

100. Lactase Deficiency: Describe "Secondary" deficiency. | Transient damage (post-infection)

101. What is the preferred diagnosis for Lactase Deficiency? | Dietary elimination trial

102. Besides elimination, what test diagnoses Lactase Deficiency? | H2 breath test

Critical Comparisons and High-Yield Distinctions

103. Distinguish Ileus vs Mechanical Obstruction: Sounds. | Ileus: Absent/minimal
     Mechanical: Hyperactive (initially)

104. Distinguish Upper GI vs Lower GI: Vomiting. | Upper: Bilious
     Lower: Feculent

105. Distinguish Crohn's vs Ulcerative Colitis: Skip vs Continuous. | CD: Skip lesions
     UC: Continuous

106. Compare Crohn's vs UC distribution. | CD: Anywhere
     UC: Rectum/colon only

107. Distinguish Crohn's vs UC: Tissue depth. | CD: Transmural
     UC: Mucosal

108. Which IBD type rarely presents with growth failure? | Ulcerative Colitis

109. Which IBD type is the hallmark for Gross rectal bleeding? | Ulcerative Colitis

110. Which IBD type is characterized by prominent perianal fistulas? | Crohn's Disease

111. What are the 3 signs in the Intussusception Triad? | Sausage mass, paroxysmal pain, currant jelly stools

112. Imaging: What does the Target sign mean? | Intussusception (U/S) or CT obstruction

113. Imaging: What does the Coiled spring indicate? | Intussusception (Barium)

114. Imaging: What does the Bird's beak indicate? | CT obstruction

115. Meconium Passage: Failure to pass meconium is an alarm for what 2 conditions? | Hirschsprung or neonatal obstruction

116. Celiac vs Lactase: Pathological difference. | Celiac: Villous atrophy
     Lactose: Enzymatic defect (no atrophy)

117. Nutrient Deficiency: Top sign in Celiac Disease? | Iron deficiency

118. Nutrient Deficiency: Hallmark of Bacterial Overgrowth? | Vitamin B12 deficiency

119. Typical Age: Intussusception peak. | 5 months to 3 years

120. Typical Age: IBD peak. | Late adolescence

121. Compare Strangulating vs Simple: Systemic signs. | Strangulating: Fever, acidosis, leukocytosis
     Simple: Mechanical symptoms

122. Celiac Serology: What must be checked alongside Anti-TG2 IgA? | Total IgA

123. Why check total IgA in Celiac screening? | Ensure IgA deficiency isn't masking results

124. What is the preferred clinical way to diagnose Lactose Intolerance? | Dietary elimination trial

8

Summary

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General Principles of Pediatric Gastrointestinal Obstruction

• Classification by Mechanism: Intestinal obstruction is classified as Functional (myopathic or neuropathic failure of peristalsis) or Mechanical (physical intraluminal or extraintestinal blockage).
• Classification by Extent: Intestinal obstruction is categorized as Partial (allows liquid/gas passage) or Complete (nothing passes).
• Localization by Vomiting Type: Upper GI obstructions typically present with bilious vomiting, while lower GI obstructions present with feculent vomiting.
• Localization by Distention: Upper GI obstructions usually show minimal distention; lower GI obstructions show significant abdominal distention.
• Classification by Blood Flow: Obstructions are either Simple (no ischemia) or Strangulating (compromised blood flow, often with absent bowel sounds and a painful mass).
• Neonatal Presentation: Warning signs of obstruction include maternal polyhydramnios, failure to pass meconium within 24-48 hours, and "currant jelly" stools.
• Radiographic Signs: Plain X-rays of intestinal obstruction show distended loops, air-fluid levels, and a paucity of colonic air.
• CT Scan Findings: The "Target sign" indicates bowel wall thickening, "Pneumatosis intestinalis" refers to air in the bowel wall, and the "beak sign" indicates distal narrowing.
• Management Priorities: Treatment for intestinal obstruction includes bowel decompression (NGT/OGT), fluid resuscitation, monitoring electrolytes, and either a conservative trial (for partial) or early surgery (for complete or malrotation).

Esophageal Atresia (EA) and Tracheoesophageal Fistula (TEF)

Hypertrophic Pyloric Stenosis (HPS)

Intestinal Atresia and Stenosis

Hirschsprung’s Disease (HD)

Functional Obstruction: Ileus

• Functional Obstruction (Ileus) refers to the failure of intestinal peristalsis without a physical blockage, often triggered by abdominal surgery (resolves in 72h), infections (AGE, pneumonia, peritonitis), or metabolic issues.
• Metabolic causes of Ileus include hypokalemia, hypercalcemia, and acidosis.
• Medications inducing Ileus include opiates, vincristine, and antimotility agents like loperamide.
• Clinical signs of Ileus include abdominal distention, nausea, vomiting, and minimal/absent bowel sounds (tympanitic abdomen).
• Diagnosis of Ileus via X-ray shows air-fluid levels without the distinct distended loops seen in mechanical obstruction.
• Management of Ileus focuses on correcting underlying abnormalities, stopping offending drugs, and nasogastric decompression.

Mechanical Obstruction: Intussusception

• Intussusception is the invagination (telescoping) of one bowel segment (intussusceptum) into another (intussuscipiens), most commonly the ileocolic type.
• Epidemiology: The peak age for intussusception is 5 months to 3 years; it is the most common abdominal emergency in children under 2.
• Lead Points: 90% are idiopathic (linked to hypertrophied Peyer's patches), but in children >2 years, lead points like Meckel diverticulum, polyps, or lymphoma are common.
• Clinical Triad: The classic triad of intussusception is paroxysmal colicky pain, "currant jelly" stools (blood + mucus), and a sausage-shaped mass in the RUQ.
• Ultrasound Signs: Diagnosis is supported by the "Target sign" or "Pseudo-kidney sign" on ultrasound.
• Radiographic Signs: Barium enema shows the "coiled spring sign".
• Conservative Management: The primary treatment for intussusception is radiologic hydrostatic reduction (fluoroscopic or U/S guided).
• Surgical Indications: Surgery for intussusception is indicated if there is shock, peritonitis, bowel necrosis, or multiple recurrences.

Meckel Diverticulum

Inflammatory Bowel Disease (IBD)

• IBD Distribution: Crohn's Disease can affect the entire tract (mouth to anus) with skip lesions; Ulcerative Colitis (UC) is continuous and limited to the colon/rectum.
• Inflammation Depth: Crohn's is transmural (entire wall); UC is limited to the mucosa.
• Hallmark Symptoms: Rectal bleeding is the hallmark of UC; Crohn's presents with abdominal pain, RLQ mass, and perianal lesions.
• Growth Failure: Significantly more common in Crohn's Disease than UC.
• Histology: Noncaseating granulomas are pathognomonic for Crohn's; UC shows crypt abscesses and distortion.
• Extraintestinal Manifestations: UC is specifically linked to pyoderma gangrenosum and primary sclerosing cholangitis.
• Diagnosis: Fecal calprotectin is used as a stool marker for inflammation; colonoscopy with biopsy is required for confirmation.
• Treatment: Mild UC is treated with aminosalicylates; IBD remission is induced with corticosteroids; biologics like Infliximab are used for severe cases.
• Dietary Therapy: Exclusive Enteral Nutrition (EEN) is a primary dietary therapy for pediatric Crohn’s Disease.

Celiac Disease and Malabsorption

• Celiac Disease is an immune-mediated disorder triggered by gluten (wheat, rye, barley) in genetically susceptible individuals (HLA-DQ2.5/DQ8).
• Extraintestinal Celiac Sign: The most common extraintestinal manifestation of Celiac is iron deficiency anemia.
• Celiac Serology: First-line test is anti-TG2 IgA; total IgA must be checked to ensure deficiency doesn't mask a negative result.
• Celiac Histology: Small bowel biopsy shows villous atrophy, crypt hyperplasia, and increased lymphocytes.
• Bacterial Overgrowth (SIBO): Small intestine colonization that causes steatorrhea (via bile salt deconjugation) and Vitamin B12 deficiency; treated with Metronidazole.
• Lactase Deficiency: Primary (physiologic decline) vs. Secondary (transient post-infection damage); diagnosed primarily via dietary elimination trial or H2 breath test.
• Short Bowel Syndrome: Defined as the loss of >50% of the small bowel.

High-Yield Comparisons for Exams

• Vomiting Color: Pyloric Stenosis is non-bilious; Duodenal Atresia and Hirschsprung's are bilious.
• Abdominal Distention: Pyloric Stenosis and Duodenal Atresia have no/minimal distention; Hirschsprung's and Lower GI Obstruction have prominent distention.
• Stool Characteristics: Intussusception has currant jelly stools; Meckel Diverticulum has maroon/brick stools; UC has gross bloody mucus stools.
• Key X-ray Signs: Duodenal Atresia shows the Double Bubble; Intussusception shows the Coiled Spring (on barium); Pyloric Stenosis shows the String Sign.
• Key Physical Exam Signs: Pyloric Stenosis has an Olive mass; Intussusception has a Sausage mass.
• Bowel Sounds: Mechanical obstruction has hyperactive sounds initially; Ileus and Strangulating obstruction have absent/minimal sounds.
• Celiac vs. Lactose Intolerance: Celiac involves villous atrophy and iron deficiency; Lactose intolerance is an enzymatic defect with no mucosal damage on biopsy.
• Crohn's vs. UC Depth: Crohn's is transmural (risk of fistulas); UC is mucosal only.
• Meconium Passage: Delayed meconium passage in a full-term infant is an alarm for Hirschsprung's Disease.
• Growth Failure: Prominent in Crohn's Disease and Celiac Disease; rare in Ulcerative Colitis.
• Anemia Type: Celiac Disease is classic for Iron deficiency; Bacterial Overgrowth (SIBO) is classic for B12 deficiency.
• EA/TEF subtypes: Pure Atresia results in a scaphoid abdomen (no air); coexisting TEF results in a gas-distended stomach.
• Crohn's vs. UC distribution: Crohn's features Skip lesions; UC features Continuous inflammation starting from the rectum.
• Age of Diagnosis: HPS (3-6 weeks); Intussusception (5mo - 3 years); Meckel (often by 2 years); IBD (late adolescence).

QA

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General Principles of Pediatric Gastrointestinal Obstruction

1. How is Intestinal Obstruction classified by mechanism? (2) | Functional and Mechanical
2. Define the mechanism of Functional Obstruction. | Myopathic or neuropathic failure of peristalsis.
3. Define the mechanism of Mechanical Obstruction. | Physical intraluminal or extraintestinal blockage.
4. How is Intestinal Obstruction categorized by extent? (2) | Partial and Complete
5. What does Partial Intestinal Obstruction allow to pass? | Liquid and gas
6. What is the characteristic of Complete Intestinal Obstruction passage? | Nothing passes
7. What type of vomiting is typical in Upper GI Obstructions? | Bilious vomiting
8. What type of vomiting is typical in Lower GI Obstructions? | Feculent vomiting
9. Contrast abdominal distention in Upper vs. Lower GI Obstruction. | Upper: Minimal distention.
   Lower: Significant distention.
10. How is Intestinal Obstruction classified by blood flow? (2) | Simple and Strangulating
11. Define Strangulating Obstruction. | Compromised blood flow.
    Often with absent bowel sounds and a painful mass.
12. What are the neonatal warning signs of Gastrointestinal Obstruction? (3) | 1) Maternal polyhydramnios
    2) Failure to pass meconium
    3) Currant jelly stools
13. Within how many hours should meconium normally be passed? | 24-48 hours
14. What are the common findings on plain X-rays of Intestinal Obstruction? (3) | 1) Distended loops
    2) Air-fluid levels
    3) Paucity of colonic air
15. What does the Target sign indicate on a CT scan? | Bowel wall thickening
16. Define the CT finding Pneumatosis intestinalis. | Air in the bowel wall
17. What does the beak sign indicate on a CT scan? | Distal narrowing
18. What are the priority treatments for Intestinal Obstruction management? (3) | 1) Bowel decompression (NGT/OGT)
    2) Fluid resuscitation
    3) Electrolyte monitoring
19. Compare management for Partial vs. Complete Obstruction. | Partial: Conservative trial.
    Complete: Early surgery.

Esophageal Atresia (EA) and Tracheoesophageal Fistula (TEF)

20. What is the pathogenesis of Esophageal Atresia? | Failure of the esophagus to develop as a continuous passage.
21. What percentage of Esophageal Atresia cases are associated with a fistula? | Over 90%
22. Enumerate the components of VACTERL syndrome. (7) | Vertebral, Anorectal, Cardiac, Tracheal, Esophageal, Renal, Limb.
23. What is the most common classification of EA/TEF? | Type C (86%)
24. Describe the anatomy of Type C EA/TEF. | Upper esophagus is atretic; distal portion connects to the trachea.
25. What is Type E (H-type) EA/TEF? | Fistula without atresia.
26. How does H-type TEF typically present? | Chronic respiratory problems.
27. What are the classic clinical signs of EA/TEF in neonates? | Frothing and bubbling at the mouth/nose.
28. List the respiratory symptoms associated with neonatal EA/TEF. (3) | 1) Coughing
    2) Cyanosis
    3) Respiratory distress
29. What is the primary bedside diagnostic test for Esophageal Atresia? | Failure to pass an NGT or OGT into the stomach.
30. What are the prenatal ultrasound findings for EA/TEF? (2) | 1) Polyhydramnios
    2) Absence of a stomach bubble
31. What does an X-ray show in a patient with Esophageal Atresia? | Coiled feeding tube in the esophageal pouch.
32. What does an airless scaphoid abdomen suggest in EA imaging? | Pure Esophageal Atresia
33. What does an air-distended stomach indicate in EA imaging? | Coexisting Tracheoesophageal Fistula (TEF)
34. Why should mechanical ventilation be avoided in EA/TEF management? | Positive pressure causes gastric distension or perforation via fistula.
35. What is the definitive treatment for EA/TEF? | Primary Complete Repair (ligation and anastomosis).
36. When is Staged Repair (gastrostomy first) indicated for EA/TEF? | High-risk infants.

Hypertrophic Pyloric Stenosis (HPS)

37. Which demographic is most affected by Hypertrophic Pyloric Stenosis? | White males.
38. Which medications are strongly associated with HPS if used in the first 2 weeks of life? | Erythromycin or macrolides.
39. What is the pathogenesis of Hypertrophic Pyloric Stenosis? | Hypertrophy of the pyloric muscle causing gastric outlet obstruction.
40. Describe the vomiting in Hypertrophic Pyloric Stenosis. | Non-bilious, projectile, and postprandial.
41. At what age does vomiting typically start in HPS? | After 3 weeks of age.
42. What is the hallmark physical exam finding for HPS? | Olive-shaped mass (2cm) in the epigastrium.
43. When is the pyloric olive mass most easily palpated? | After vomiting.
44. What visible sign may be seen on the abdomen of an HPS patient? | Gastric peristaltic waves.
45. Describe the classic metabolic profile of Hypertrophic Pyloric Stenosis. | Hypochloremic metabolic alkalosis.
46. What is Icteropyloric Syndrome? | Unconjugated hyperbilirubinemia associated with HPS.
47. What is the sensitive diagnostic tool for HPS? | Ultrasound (95% sensitivity).
48. What are the ultrasound criteria for Pyloric Stenosis? | Thickness: 3-4mm; Length: 15-19mm.
49. List 3 contrast imaging signs of Pyloric Stenosis. | 1) String sign
    2) Shoulder sign
    3) Double tract sign
50. What is the initial management priority for HPS? | Fluid and electrolyte correction.
51. What is the surgical procedure of choice for HPS? | Pyloromyotomy.

Intestinal Atresia and Stenosis

52. What is the pathogenesis of Duodenal Atresia? | Failed recanalization of the intestinal lumen.
53. During which weeks of gestation does duodenal recanalization fail? | 6th-7th week.
54. Duodenal Atresia is associated with which chromosomal abnormality? | Trisomy 21 (Down Syndrome).
55. What is the hallmark clinical presentation of Duodenal Atresia? | Bilious vomiting WITHOUT abdominal distention.
56. What prenatal history is often present in Duodenal Atresia? | Maternal polyhydramnios.
57. What is the classic X-ray sign for Duodenal Atresia? | Double bubble sign.
58. What does the Double Bubble represent? | Air in the stomach and proximal duodenum.
59. What is the surgical treatment for Duodenal Atresia? | Duodenoduodenostomy.
60. What is the typical cause of Jejunoileal Atresia? | Intrauterine vascular accidents.
61. Compare Jejunoileal and Duodenal Atresia regarding extraintestinal anomalies. | Jejunoileal atresia is not typically associated with extraintestinal anomalies.

Hirschsprung’s Disease (HD)

62. What is the pathogenesis of Hirschsprung’s Disease? | Failure of neuroblasts to migrate, resulting in absence of ganglion cells.
63. Which nerve plexuses are absent in Hirschsprung’s Disease? | Meissner and Auerbach plexuses.
64. What is the functional result of the absence of ganglion cells in HD? | Lack of bowel relaxation and functional obstruction.
65. What is the most common cause of lower GI obstruction in neonates? | Hirschsprung’s Disease.
66. What is the Male-to-Female ratio in Hirschsprung’s Disease? | 4:1.
67. Which gene and syndrome are strongly linked to Hirschsprung’s Disease? | RET gene and Trisomy 21.
68. When should Hirschsprung’s Disease be suspected in a full-term infant? | Delayed passage of meconium (>24-48 hours).
69. What physical exam finding occurs during a DRE in Hirschsprung’s Disease? | Explosive stool passage.
70. What is the Gold Standard for diagnosing Hirschsprung’s Disease? | Rectal Suction Biopsy.
71. What does histology show in Hirschsprung’s Disease biopsy? | Absence of ganglion cells and hypertrophied nerve bundles.
72. What barium enema finding is highly suggestive of Hirschsprung’s Disease? | Rectal:Sigmoid diameter ratio of ≤1 (Transition zone).
73. What is the most serious complication of Hirschsprung’s Disease? | Enterocolitis (Hirschsprung’s-associated enterocolitis).
74. How does Hirschsprung’s Enterocolitis present? (3) | Sepsis, fever, and explosive diarrhea.
75. What is the definitive surgical treatment for Hirschsprung’s Disease? | Primary pull-through procedure (ex: Soave).
76. When is staged surgery with an ostomy used for HD? | If enterocolitis is present.

Functional Obstruction: Ileus

77. Define Functional Obstruction (Ileus). | Failure of intestinal peristalsis without a physical blockage.
78. How long does post-abdominal surgery Ileus typically take to resolve? | Within 72 hours.
79. List 3 metabolic causes of Ileus. | 1) Hypokalemia
    2) Hypercalcemia
    3) Acidosis.
80. Which medications can induce Ileus? (3) | Opiates, vincristine, and antimotility agents (loperamide).
81. What are the clinical signs of Ileus? (4) | 1) Abdominal distention
    2) Nausea
    3) Vomiting
    4) Minimal/absent bowel sounds.
82. What does an X-ray show in Ileus compared to mechanical obstruction? | Air-fluid levels without distinct distended loops.
83. What are the management focuses for Ileus? (3) | 1) Correct underlying abnormalities
    2) Stop offending drugs
    3) Nasogastric decompression.

Mechanical Obstruction: Intussusception

84. Define Intussusception. | Invagination (telescoping) of one bowel segment into another.
85. Define Intussusceptum vs Intussuscipiens. | Intussusceptum: Inner segment that telescopes.
    Intussuscipiens: Outer segment receiving it.
86. What is the most common type of Intussusception? | Ileocolic.
87. What is the peak age range for Intussusception? | 5 months to 3 years.
88. What is the most common abdominal emergency in children under 2? | Intussusception.
89. What is the idiopathic cause of Intussusception linked to? | Hypertrophied Peyer's patches.
90. Name 3 potential lead points for Intussusception in children >2 years. | 1) Meckel diverticulum
    2) Polyps
    3) Lymphoma.
91. What is the classic clinical triad of Intussusception? | Paroxysmal colicky pain, currant jelly stools, and a sausage-shaped mass.
92. Where is the sausage-shaped mass typically palpated in intussusception? | Right Upper Quadrant (RUQ).
93. Describe currant jelly stools. | Blood mixed with mucus.
94. What are the ultrasound signs of Intussusception? (2) | 1) Target sign
    2) Pseudo-kidney sign.
95. What barium enema sign is characteristic of Intussusception? | Coiled spring sign.
96. What is the primary conservative treatment for Intussusception? | Radiologic hydrostatic reduction (fluoroscopic or U/S guided).
97. List 4 indications for surgery in intussusception. | 1) Shock
    2) Peritonitis
    3) Bowel necrosis
    4) Multiple recurrences.

Meckel Diverticulum

98. What is the most common congenital GI anomaly? | Meckel Diverticulum.
99. What is the pathogenesis of Meckel Diverticulum? | Incomplete obliteration of the omphalomesenteric duct.
100. Enumerate the Meckel Rule of 2s. (5) | 1) 2% of population
     2) Symptomatic by age 2
     3) 2 inches long
     4) 2 feet from ileocecal valve
     5) 2 ectopic tissues.
101. What are the 2 types of ectopic tissue found in Meckel Diverticulum? | Gastric and pancreatic.
102. Describe the classic clinical presentation of Meckel Diverticulum. | Painless rectal bleeding.
103. How is the stool described in Meckel Diverticulum? | Brick-colored or maroon.
104. Which diagnostic test detects ectopic gastric mucosa in Meckel Diverticulum? | Meckel radionuclide scan (Technetium-99m).
105. What is the standard surgical treatment for Meckel Diverticulum? | Diverticulectomy.

Inflammatory Bowel Disease (IBD)

106. Compare the distribution of Crohn's Disease vs. Ulcerative Colitis. | Crohn's: Entire tract (mouth to anus) with skip lesions.
     UC: Continuous and limited to colon/rectum.
107. Compare the depth of inflammation in Crohn's vs. UC. | Crohn's: Transmural.
     UC: Mucosa only.
108. What is the hallmark symptom of Ulcerative Colitis? | Rectal bleeding.
109. List 3 classic symptoms of Crohn's Disease. | 1) Abdominal pain
     2) RLQ mass
     3) Perianal lesions.
110. In which type of IBD is growth failure more common? | Crohn's Disease.
111. What histological finding is pathognomonic for Crohn's Disease? | Noncaseating granulomas.
112. What histological findings are seen in Ulcerative Colitis? | Crypt abscesses and distortion.
113. List 2 extraintestinal manifestations specific to Ulcerative Colitis. | 1) Pyoderma gangrenosum
     2) Primary sclerosing cholangitis.
114. What stool marker is used for IBD inflammation? | Fecal calprotectin.
115. What is required for definitive confirmation of IBD diagnosis? | Colonoscopy with biopsy.
116. How is mild UC treated? | Aminosalicylates.
117. What medication is used to induce IBD remission? | Corticosteroids.
118. Which biologic is used for severe IBD cases? | Infliximab.
119. What is Exclusive Enteral Nutrition (EEN) used for? | Primary dietary therapy for pediatric Crohn's Disease.

Celiac Disease and Malabsorption

120. Define Celiac Disease pathogenesis. | Immune-mediated disorder triggered by gluten in genetically susceptible individuals (HLA-DQ2.5/DQ8).
121. Name 3 grains containing gluten. | Wheat, rye, barley.
122. What is the most common extraintestinal manifestation of Celiac Disease? | Iron deficiency anemia.
123. What is the first-line serological test for Celiac Disease? | Anti-TG2 IgA.
124. Why must total IgA be checked during Celiac screening? | Deficiency can mask a negative anti-TG2 result.
125. What does the histology of Celiac Disease show? (3) | 1) Villous atrophy
     2) Crypt hyperplasia
     3) Increased lymphocytes.
126. What causes steatorrhea and B12 deficiency in SIBO? | Bacterial colonization causing bile salt deconjugation.
127. How is Bacterial Overgrowth (SIBO) treated? | Metronidazole.
128. Contrast Primary vs. Secondary Lactase Deficiency. | Primary: Physiologic decline.
     Secondary: Transient post-infection damage.
129. How is Lactase Deficiency primarily diagnosed? | Dietary elimination trial or H2 breath test.
130. Define Short Bowel Syndrome. | Loss of >50% of the small bowel.

High-Yield Comparisons for Exams

131. Compare vomiting color: Pyloric Stenosis vs. Duodenal Atresia. | Pyloric Stenosis: Non-bilious.
     Duodenal Atresia: Bilious.
132. Compare abdominal distention: Pyloric Stenosis vs. Hirschsprung's. | Pyloric Stenosis: No/minimal.
     Hirschsprung's: Prominent.
133. Compare stool type: Intussusception vs. Meckel Diverticulum. | Intussusception: Currant jelly.
     Meckel: Maroon/brick.
134. What stool type is seen in Ulcerative Colitis? | Gross bloody mucus stools.
135. Compare X-ray signs: Duodenal Atresia vs. Pyloric Stenosis. | Duodenal Atresia: Double Bubble.
     Pyloric Stenosis: String Sign.
136. What is the physical mass description for Pyloric Stenosis? | Olive mass.
137. What is the physical mass description for Intussusception? | Sausage mass.
138. Compare bowel sounds: Mechanical Obstruction vs. Ileus. | Mechanical: Hyperactive initially.
     Ileus: Absent/minimal.
139. Compare Celiac vs. Lactose Intolerance on biopsy. | Celiac: Villous atrophy.
     Lactose Intolerance: No mucosal damage.
140. Compare Crohn's vs. UC regarding complication risk. | Crohn's: Transmural (fistulas).
     UC: Mucosal only.
141. What is the Meconium alarm sign for Hirschsprung's Disease? | Delayed passage in a full-term infant.
142. Compare growth failure in Crohn's vs. UC. | Prominent in Crohn's; rare in UC.
143. Compare anemia type: Celiac vs. SIBO. | Celiac: Iron deficiency.
     SIBO: B12 deficiency.
144. Compare EA/TEF abdomen: Pure Atresia vs. Atresia + TEF. | Pure atresia: Scaphoid (no air).
     Atresia + TEF: Gas-distended.
145. Compare distribution: Crohn's vs. Ulcerative Colitis. | Crohn's: Skip lesions.
     UC: Continuous from the rectum.
146. Compare age of diagnosis for HPS vs. Intussusception. | HPS: 3-6 weeks.
     Intussusception: 5 months - 3 years.
147. When is IBD commonly diagnosed? | Late adolescence.

9

Summary

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Neonatal Cholestasis: General Principles

• In Neonatal Cholestasis, the first and most important laboratory test is bilirubin fractionation to determine if the elevation is direct (conjugated) or indirect.
• Icteropyloric Syndrome in the source text context usually refers to unconjugated hyperbilirubinemia, but in Neonatal Cholestasis, the focus is always on the conjugated fraction.
• Parenteral Nutrition-Associated Cholestasis (PNAC) occurs in 1/5 of neonates receiving PN for >2 weeks; risk factors include prematurity and sepsis.
• Ursodeoxycholic acid is used in Neonatal Cholestasis to increase bile secretion, but it is ineffective if there is a physical obstruction (e.g., Biliary Atresia).
• Galactosemia and Tyrosinemia, which cause cholestasis, are detectable via the Philippine Expanded Newborn Screening program.

Major Extrahepatic Causes of Cholestasis

• Inspissated Bile Syndrome is a rare cause of cholestasis where bile plugs or sludge obstruct the ducts, often linked to hemolysis or drugs like Ceftriaxone.
• In Biliary Atresia, the Kasai Procedure has a 90% success rate if performed before the 8th week of life.
• Choledochal Cyst in infants presents with cholestatic jaundice and severe liver dysfunction (ascites, coagulopathy).

Idiopathic Neonatal Hepatitis (INH)

• Idiopathic Neonatal Hepatitis (INH), also known as Giant Cell Hepatitis, is a diagnosis of exclusion accounting for 13-30% of NC cases.
• The histologic hallmark of Idiopathic Neonatal Hepatitis is Giant cell transformation and lobular disarray.
• Idiopathic Neonatal Hepatitis can be sporadic or familial; the familial form often suggests an underlying genetic or metabolic aberration.

Viral Hepatitis Basics

• Viral Hepatitis pathogenesis is usually immune-mediated (especially HBV), with necrosis most marked in centrilobular areas.
• Hepatitis C (HCV) is unique among hepatotropic viruses because fatty exchange (steatosis) is a common histologic finding.
• In Acute Viral Hepatitis, the liver morphology typically returns to normal within 3 months of infection.
• Hepatitis A period of communicability is 2 weeks before to 7 days after the onset of jaundice.
• Hepatitis A diagnosis is confirmed by Anti-HAV IgM, which is detectable when symptoms appear and remains for 4-6 months.
• Hepatitis A Vaccination is given as a 2-dose series starting at 12 months of age, with at least a 6-month interval.

Hepatitis B (HBV) Management

• The most important risk factor for acquiring Hepatitis B in children is perinatal exposure; infants of HBeAg-positive mothers have a 90% risk of chronic infection if untreated.
• The first biochemical evidence of HBV infection is an elevation of ALT levels, occurring 6-7 weeks after exposure.
• HBsAg (Surface Antigen) presence indicates active infection (acute or chronic).
• Anti-HBs (Surface Antibody) indicate immunity via either resolved infection or vaccination.
• IgM anti-HBc (Core Antibody) is the hallmark marker for recent or acute HBV infection.
• HBeAg (e-Antigen) correlates with active viral replication and high infectivity.
• For newborns weight ≥2kg born to HBsAg(+) mothers, administer both HBV vaccine and HBIG within 12 hours of life.
• If a newborn is &lt2kg, the birth dose of HBV vaccine does NOT count toward the 3-dose series; 3 additional doses are required.

Liver Abscess

• Staphylococcus aureus is the leading single pathogenic agent for Liver Abscess in children without underlying intestinal disease.
• The most common routes for Liver Abscess include the portal vein (from omphalitis or appendicitis) and the hepatic artery (from sepsis).
• Liver Abscess imaging: Ultrasound/CT is preferred; 75% are located in the right lobe and 70% are solitary.
• Liver Abscess treatment involves 2-3 weeks of IV antibiotics followed by oral therapy to complete a 4-6 week course.
• Amoebic Liver Abscess requires treatment with Metronidazole plus Paromomycin.

Cholelithiasis (Gallstones)

• Pigment stones account for 70% of pediatric gallstones, while cholesterol stones comprise 15-20%.
• Biliary Pseudolithiasis is a unique condition caused by high-dose Ceftriaxone use (>10 days) resulting in calcium-ceftriaxone salt precipitates.
• Biliary Pseudolithiasis typically resolves spontaneously within weeks to months after discontinuing Ceftriaxone.
• The hallmark clinical feature of Cholelithiasis is recurrent abdominal colicky pain in the Right Upper Quadrant (RUQ).
• Laparoscopic Cholecystectomy is the treatment of choice for symptomatic children with gallstones.

High-Yield Comparisons for Differentiation

1. Biliary Atresia vs. Choledochal Cyst (Infant Presentation): Both present with NC, but Biliary Atresia is characterized by a "disappearing" or obliterated biliary tree, while Choledochal Cyst shows a distinct dilation on ultrasound.
2. Biliary Atresia vs. Idiopathic Neonatal Hepatitis (INH) on Biopsy: Biliary Atresia shows bile duct proliferation; INH shows giant cell transformation and lobular disarray.
3. Kasai Procedure vs. Liver Transplant: Kasai is a temporizing measure to slow progression to cirrhosis and sustain growth; Liver Transplant is the definitive treatment for Biliary Atresia.
4. Hepatitis A vs. Hepatitis B transmission: HAV is fecal-oral (associated with hygiene and food); HBV is parenteral/perinatal (associated with body fluids).
5. Gilbert Syndrome vs. Crigler-Najjar Type 1: Both involve UDPGT, but Gilbert is impaired function (mild, stress-induced), whereas Crigler-Najjar Type 1 is a complete absence of the enzyme (severe).
6. HBeAg vs. Anti-HBe: HBeAg indicates active replication and high contagiousness; Anti-HBe (seroconversion) signals that active replication has ceased.
7. HBsAg vs. Anti-HBs: HBsAg means you HAVE the virus (infection); Anti-HBs means you are PROTECTED from the virus (immunity).
8. Biliary Atresia vs. Choledochal Cyst Mass: A palpable RUQ mass is part of the classic triad for Choledochal Cyst but is generally not a feature of Biliary Atresia.
9. Staphylococcus aureus vs. Entamoeba histolytica Abscess: S. aureus is the most common pyogenic cause; E. histolytica is the amoebic cause requiring Metronidazole + Paromomycin.
10. Dubin-Johnson vs. Rotor Syndrome: Both are causes of conjugated hyperbilirubinemia in older children (along with Wilson's and Alpha-1 antitrypsin deficiency).
11. Pre-exposure vs. Post-exposure HAV prophylaxis: HAV vaccine is preferred for both in healthy persons if the exposure was within the last 2 weeks.
12. Pigment vs. Cholesterol Stones: In children, pigment stones are much more common (70%) compared to adults where cholesterol stones predominate.
13. Hepatitis C vs. others on histology: Think Fat/Steatosis for Hepatitis C; think Giant cells for neonatal viral infections.
14. Ascites vs. Coagulopathy in NC: In cholestasis, Ascites is usually due to low albumin (synthetic failure), while Coagulopathy is due to Vitamin K malabsorption (obstructive/cholestatic failure).

QA

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Neonatal Cholestasis: General Principles

1. Define Neonatal Cholestasis based on the period of occurrence. | First 28 days of life
2. What is the Definition of Neonatal Cholestasis regarding bile? | Reduction in bile formation or excretion
3. Biochemical Criteria: Neonatal Cholestasis when Total Bilirubin (TB) is ≤5 mg/dL. | Direct Bilirubin >1.0 mg/dL
4. Biochemical Criteria: Neonatal Cholestasis when Total Bilirubin (TB) is >5 mg/dL. | Direct Bilirubin ≥20% of TB
5. Describe the urine in Neonatal Cholestasis. | Highly staining (dark yellow)
6. Describe the stools in Neonatal Cholestasis. | Acholic (pale, white, or light yellow)
7. What physical finding regarding the liver is a typical feature of Neonatal Cholestasis? | Hepatomegaly
8. What is the medical term for scleral discoloration in Neonatal Cholestasis? | Icterus
9. List the common intrahepatic causes (4) of Neonatal Cholestasis. | 1) Idiopathic neonatal hepatitis
   2) TORCH infections
   3) Metabolic diseases
   4) Prolonged TPN
10. Identify the metabolic diseases (2) causing intrahepatic Neonatal Cholestasis. | Galactosemia and Tyrosinemia
11. What duration of Total Parenteral Nutrition (TPN) is a common cause of Neonatal Cholestasis? | >2 weeks
12. List the common extrahepatic causes (2) of Neonatal Cholestasis. | Biliary Atresia and Choledochal cyst
13. What complication results from the failure of bile delivery in Neonatal Cholestasis? | Malabsorption
14. Malabsorption in Neonatal Cholestasis specifically affects which substances (2)? | Fats and fat-soluble vitamins
15. What are the clinical consequences of fat malabsorption in Neonatal Cholestasis (3)? | 1) Malnutrition
    2) Growth retardation
    3) Steatorrhea
16. How does Portal Hypertension manifest in the context of Neonatal Cholestasis (3)? | 1) Hypersplenism
    2) Ascites
    3) Varices
17. What is the cause of ascites in Neonatal Cholestasis with portal hypertension? | Hypoalbuminemia
18. What are the clinical signs of varices in Neonatal Cholestasis (2)? | Hematemesis or hematochezia
19. What is the first and most important laboratory test for Neonatal Cholestasis? | Bilirubin fractionation
20. Why is bilirubin fractionation performed in Neonatal Cholestasis? | Determine if elevation is direct or indirect
21. What fraction of bilirubin is the focus in Neonatal Cholestasis? | Conjugated fraction
22. Icteropyloric Syndrome usually refers to which type of hyperbilirubinemia? | Unconjugated hyperbilirubinemia
23. What is the incidence of Parenteral Nutrition-Associated Cholestasis (PNAC) in neonates on PN for >2 weeks? | 1/5 of neonates
24. List risk factors (2) for Parenteral Nutrition-Associated Cholestasis (PNAC). | Prematurity and sepsis
25. What is the function of Ursodeoxycholic acid in Neonatal Cholestasis? | Increase bile secretion
26. When is Ursodeoxycholic acid ineffective in treating cholestasis? | Physical obstruction (Biliary Atresia)
27. How are Galactosemia and Tyrosinemia detected in the Philippines? | Philippine Expanded Newborn Screening

Major Extrahepatic Causes: Biliary Atresia and Choledochal Cyst

28. Define the pathogenesis of Biliary Atresia. | Progressive fibroinflammatory obliteration
29. Which part of the anatomy is obliterated in Biliary Atresia? | Extrahepatic biliary tree
30. Define the pathogenesis of Choledochal Cyst. | Congenital dilation of biliary tree
31. What is the epidemiology of Biliary Atresia? | Most common and severe cause
32. In which geographic region is Biliary Atresia particularly common? | East Asia
33. What is the epidemiology of Choledochal Cyst? | 2-3% of NC cases
34. Which gender has a significant predominance in Choledochal Cyst cases? | Female predominance
35. How does the jaundice present in Biliary Atresia? | Normal at birth, persists >2 weeks
36. Identify the Classic Triad for Choledochal Cyst in older children. | 1) Abdominal pain
    2) Jaundice
    3) Palpable mass
37. List associated anomalies (3) found in Biliary Atresia. | 1) Polysplenia
    2) Situs inversus
    3) Cardiac anomalies
38. What are common complications (3) of Choledochal Cyst? | 1) Cholangitis
    2) Pancreatitis
    3) Malignant transformation
39. What is the diagnostic hallmark on liver biopsy for Biliary Atresia? | Bile duct proliferation
40. Describe the perilobular status in a Biliary Atresia liver biopsy. | Perilobular fibrosis with intact architecture
41. What imaging modalities (2) show a Choledochal Cyst? | Ultrasound or MRCP
42. Which type of Choledochal Cyst is the most common? | Type I (70-90%)
43. What is the primary surgical management for Biliary Atresia? | Kasai hepatoportoenterostomy
44. When is the best time to perform a Kasai procedure? | Before 8 weeks
45. What is the definitive treatment for Biliary Atresia? | Liver transplant
46. What is the management for Choledochal Cyst? | Primary excision of the cyst
47. Which reconstructive surgery follows cyst excision in Choledochal Cyst? | Roux-en-Y choledochojejunostomy
48. What causes duct obstruction in Inspissated Bile Syndrome? | Bile plugs or sludge
49. Which antibiotic is linked to Inspissated Bile Syndrome? | Ceftriaxone
50. What condition is often linked to Inspissated Bile Syndrome besides drugs? | Hemolysis
51. What is the success rate of the Kasai Procedure if performed before the 8th week? | 90% success rate
52. How does Choledochal Cyst present specifically in infants? | Cholestatic jaundice and liver dysfunction
53. Name signs of severe liver dysfunction (2) in infants with Choledochal Cyst. | Ascites and coagulopathy

Idiopathic Neonatal Hepatitis (INH)

54. What is the alternative name for Idiopathic Neonatal Hepatitis? | Giant Cell Hepatitis
55. What percentage of Neonatal Cholestasis cases are attributed to Idiopathic Neonatal Hepatitis? | 13-30% of cases
56. Idiopathic Neonatal Hepatitis is considered what type of diagnosis? | Diagnosis of exclusion
57. What is the histologic hallmark of Idiopathic Neonatal Hepatitis? | Giant cell transformation
58. Describe the lobular architecture in Idiopathic Neonatal Hepatitis. | Lobular disarray
59. What does the familial form of Idiopathic Neonatal Hepatitis often suggest? | Genetic or metabolic aberration

Viral Hepatitis Basics

60. Identify the virus type and family for Hepatitis A (HAV). | RNA (Picornavirus)
61. What is the transmission route for Hepatitis A? | Fecal-oral
62. What is the incubation period for Hepatitis A? | 15-49 days (Shortest)
63. Is there a chronic risk for Hepatitis A? | No
64. Identify the virus type and family for Hepatitis B (HBV). | dsDNA (Hepadnaviridae)
65. What are the transmission routes (2) for Hepatitis B? | Perinatal and Blood
66. What is the average incubation period for Hepatitis B? | 3 months
67. Is there a chronic risk for Hepatitis B? | Yes (High in neonates)
68. What is the virus type for Hepatitis C (HCV)? | RNA
69. What are the transmission routes (2) for Hepatitis C? | Perinatal and Blood
70. Is there a chronic risk for Hepatitis C? | Yes
71. What is the usual pathogenesis of Viral Hepatitis damage? | Immune-mediated
72. In Viral Hepatitis, where is necrosis most marked? | Centrilobular areas
73. What unique histologic finding is associated with Hepatitis C? | Fatty exchange (steatosis)
74. How long does it take for liver morphology to return to normal in Acute Viral Hepatitis? | Within 3 months
75. What is the period of communicability for Hepatitis A? | 2 weeks before to 7 days after jaundice
76. Which marker confirms the diagnosis of Hepatitis A? | Anti-HAV IgM
77. How long does Anti-HAV IgM remain detectable? | 4-6 months
78. What is the Hepatitis A Vaccination schedule? | 2nd-dose series starting at 12 months
79. What is the minimum interval between Hepatitis A vaccine doses? | 6-month interval

Hepatitis B (HBV) Management

80. What is the most important risk factor for acquiring Hepatitis B in children? | Perinatal exposure
81. What is the risk of chronic infection in infants of HBeAg-positive mothers? | 90% risk if untreated
82. What is the first biochemical evidence of HBV infection? | Elevation of ALT levels
83. When does ALT elevate after HBV exposure? | 6-7 weeks after exposure
84. What does the presence of HBsAg indicate? | Active infection (acute/chronic)
85. What does the presence of Anti-HBs indicate? | Immunity
86. What are the two ways to acquire Anti-HBs? | Resolved infection or vaccination
87. What is the hallmark marker for recent or acute HBV infection? | IgM anti-HBc (Core Antibody)
88. What does HBeAg correlate with? | Active viral replication
89. Higher infectivity in HBV is indicated by which marker? | HBeAg (e-Antigen)
90. Management for newborns ≥2kg from HBsAg(+) mothers? | HBV vaccine and HBIG within 12 hours
91. Management for newborns &lt2kg regarding the HBV birth dose? | 3 additional doses required (birth dose doesn't count)

Liver Abscess

92. Leading pathogenic agent for Liver Abscess (no intestinal disease)? | Staphylococcus aureus
93. Portal vein route for Liver Abscess usually originates from (2)? | Omphalitis or appendicitis
94. Hepatic artery route for Liver Abscess usually originates from? | Sepsis
95. Preferred imaging for Liver Abscess? | Ultrasound or CT
96. Typical location and number for Liver Abscess? | 75% Right lobe; 70% Solitary
97. Initial treatment duration for Liver Abscess? | 2-3 weeks of IV antibiotics
98. Total treatment course duration for Liver Abscess? | 4-6 weeks total
99. Treatment for Amoebic Liver Abscess? | Metronidazole plus Paromomycin