LATEST PEDIATRIC INFECTIOUS DISEASES
CERTIFICATION EXAM OFFERED BY
AMERICAN BOARD OF PEDIATRICS |
COMPLETE EXAM Q&A WITH RATIONALES
1. A 6-month-old infant presents with fever (39.5°C),
irritability, and a bulging fontanelle. Lumbar puncture
reveals 500 WBC/μL (90% neutrophils), glucose 20
mg/dL (serum 90 mg/dL), and protein 150 mg/dL.
Gram stain shows gram-positive cocci in pairs and
chains. What is the most likely pathogen?
A) Group B Streptococcus (Streptococcus
agalactiae)
B) Streptococcus pneumoniae
C) Neisseria meningitidis
D) Listeria monocytogenes
Correct answer: A
Rationale: In a 6-month-old, Group B Streptococcus
(GBS) is a common cause of bacterial meningitis,
especially if the infant is unvaccinated. S.
pneumoniae (B) is more common after 2 months of
age but GBS is still prevalent in infants under 3
months.
,2. A 5-year-old child presents with a 2-week history of
fever, headache, and vomiting. On examination, there
is nuchal rigidity and a petechial rash. Lumbar
puncture shows 1,000 WBC/μL (80% neutrophils),
glucose 25 mg/dL, protein 200 mg/dL. Gram stain is
negative. Blood culture grows Neisseria meningitidis.
What is the most appropriate antibiotic?
A) Ceftriaxone (third-generation cephalosporin)
B) Vancomycin + ceftriaxone
C) Ampicillin + gentamicin
D) Meropenem
Correct answer: A
Rationale: Neisseria meningitidis is treated with third-
generation cephalosporin (ceftriaxone or
cefotaxime). Vancomycin (B) is added if penicillin-
resistant pneumococcus is suspected.
Chemoprophylaxis for close contacts: rifampin,
ciprofloxacin, or ceftriaxone.
3. A 4-year-old child presents with a 3-day history of
fever, cough, and coryza, followed by a
maculopapular rash starting on the face and
spreading downward. Koplik spots are present on the
buccal mucosa. The child is unvaccinated. What is
the most likely diagnosis?
,A) Measles (rubeola)
B) Rubella (German measles)
C) Erythema infectiosum (parvovirus B19)
D) Roseola (HHV-6)
Correct answer: A
Rationale: Measles (paramyxovirus) presents with
prodrome (cough, coryza, conjunctivitis, Koplik
spots) followed by rash starting on face.
Complications include pneumonia, encephalitis, and
subacute sclerosing panencephalitis (SSPE). Vitamin
A reduces morbidity and mortality.
4. A 2-year-old child presents with a 2-day history of
fever, sore throat, and a sandpaper-like rash on the
trunk and extremities (spares the face). There is
circumoral pallor and Pastia lines (hyperpigmented
lines in skin folds). What is the most likely diagnosis?
A) Scarlet fever (Group A Streptococcus, GAS)
B) Kawasaki disease (fever >5 days, other criteria)
C) Measles (Koplik spots)
D) Toxic shock syndrome (hypotension, multiorgan)
Correct answer: A
Rationale: Scarlet fever is caused by Group A
Streptococcus (GAS) toxin (erythrogenic toxin).
, Treatment: penicillin (or amoxicillin) for 10 days to
prevent rheumatic fever. Rapid strep test or throat
culture is diagnostic.
5. A 6-month-old infant with a history of severe
combined immunodeficiency (SCID) presents with
fever, cough, and tachypnea. Chest X-ray shows
bilateral interstitial infiltrates. Bronchoalveolar
lavage (BAL) shows Pneumocystis jirovecii cysts
(silver stain positive). What is the most appropriate
treatment?
A) Trimethoprim-sulfamethoxazole (TMP-SMX) (IV or
oral)
B) Pentamidine (IV)
C) Corticosteroids (adjunctive for severe hypoxia)
D) Clindamycin + primaquine
Correct answer: A
Rationale: PJP (Pneumocystis jirovecii pneumonia) is
treated with TMP-SMX (first-line). Corticosteroids are
indicated for moderate-to-severe PJP (PaO2 <70 mm
Hg or A-a gradient >35). Prophylaxis: TMP-SMX for at-
risk immunocompromised children.
6. A 15-year-old boy presents with a 2-week history of
fever, night sweats, weight loss, and a dry cough.
CERTIFICATION EXAM OFFERED BY
AMERICAN BOARD OF PEDIATRICS |
COMPLETE EXAM Q&A WITH RATIONALES
1. A 6-month-old infant presents with fever (39.5°C),
irritability, and a bulging fontanelle. Lumbar puncture
reveals 500 WBC/μL (90% neutrophils), glucose 20
mg/dL (serum 90 mg/dL), and protein 150 mg/dL.
Gram stain shows gram-positive cocci in pairs and
chains. What is the most likely pathogen?
A) Group B Streptococcus (Streptococcus
agalactiae)
B) Streptococcus pneumoniae
C) Neisseria meningitidis
D) Listeria monocytogenes
Correct answer: A
Rationale: In a 6-month-old, Group B Streptococcus
(GBS) is a common cause of bacterial meningitis,
especially if the infant is unvaccinated. S.
pneumoniae (B) is more common after 2 months of
age but GBS is still prevalent in infants under 3
months.
,2. A 5-year-old child presents with a 2-week history of
fever, headache, and vomiting. On examination, there
is nuchal rigidity and a petechial rash. Lumbar
puncture shows 1,000 WBC/μL (80% neutrophils),
glucose 25 mg/dL, protein 200 mg/dL. Gram stain is
negative. Blood culture grows Neisseria meningitidis.
What is the most appropriate antibiotic?
A) Ceftriaxone (third-generation cephalosporin)
B) Vancomycin + ceftriaxone
C) Ampicillin + gentamicin
D) Meropenem
Correct answer: A
Rationale: Neisseria meningitidis is treated with third-
generation cephalosporin (ceftriaxone or
cefotaxime). Vancomycin (B) is added if penicillin-
resistant pneumococcus is suspected.
Chemoprophylaxis for close contacts: rifampin,
ciprofloxacin, or ceftriaxone.
3. A 4-year-old child presents with a 3-day history of
fever, cough, and coryza, followed by a
maculopapular rash starting on the face and
spreading downward. Koplik spots are present on the
buccal mucosa. The child is unvaccinated. What is
the most likely diagnosis?
,A) Measles (rubeola)
B) Rubella (German measles)
C) Erythema infectiosum (parvovirus B19)
D) Roseola (HHV-6)
Correct answer: A
Rationale: Measles (paramyxovirus) presents with
prodrome (cough, coryza, conjunctivitis, Koplik
spots) followed by rash starting on face.
Complications include pneumonia, encephalitis, and
subacute sclerosing panencephalitis (SSPE). Vitamin
A reduces morbidity and mortality.
4. A 2-year-old child presents with a 2-day history of
fever, sore throat, and a sandpaper-like rash on the
trunk and extremities (spares the face). There is
circumoral pallor and Pastia lines (hyperpigmented
lines in skin folds). What is the most likely diagnosis?
A) Scarlet fever (Group A Streptococcus, GAS)
B) Kawasaki disease (fever >5 days, other criteria)
C) Measles (Koplik spots)
D) Toxic shock syndrome (hypotension, multiorgan)
Correct answer: A
Rationale: Scarlet fever is caused by Group A
Streptococcus (GAS) toxin (erythrogenic toxin).
, Treatment: penicillin (or amoxicillin) for 10 days to
prevent rheumatic fever. Rapid strep test or throat
culture is diagnostic.
5. A 6-month-old infant with a history of severe
combined immunodeficiency (SCID) presents with
fever, cough, and tachypnea. Chest X-ray shows
bilateral interstitial infiltrates. Bronchoalveolar
lavage (BAL) shows Pneumocystis jirovecii cysts
(silver stain positive). What is the most appropriate
treatment?
A) Trimethoprim-sulfamethoxazole (TMP-SMX) (IV or
oral)
B) Pentamidine (IV)
C) Corticosteroids (adjunctive for severe hypoxia)
D) Clindamycin + primaquine
Correct answer: A
Rationale: PJP (Pneumocystis jirovecii pneumonia) is
treated with TMP-SMX (first-line). Corticosteroids are
indicated for moderate-to-severe PJP (PaO2 <70 mm
Hg or A-a gradient >35). Prophylaxis: TMP-SMX for at-
risk immunocompromised children.
6. A 15-year-old boy presents with a 2-week history of
fever, night sweats, weight loss, and a dry cough.
