ABIM Infectious Disease Certification Exam
Questions WITH CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2026 Q&A |INSTANT
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1. A 65-year-old man presents with fever, malaise, and cough.
He has a history of COPD and recently completed a course of
antibiotics. Chest X-ray shows a new infiltrate. Which
organism is most likely?
A. Streptococcus pneumoniae
B. Pseudomonas aeruginosa
C. Klebsiella pneumoniae
D. Haemophilus influenzae
Answer: B. Pseudomonas aeruginosa
Rationale: In patients with COPD and recent antibiotic exposure,
Pseudomonas is a common cause of hospital- or healthcare-
associated pneumonia.
2. Which of the following is the most sensitive test for latent
tuberculosis infection?
A. Tuberculin skin test (TST)
B. Chest X-ray
C. Interferon-gamma release assay (IGRA)
D. Sputum acid-fast bacilli smear
,Answer: C. Interferon-gamma release assay (IGRA)
Rationale: IGRA is more specific than TST, especially in patients
vaccinated with BCG.
3. A patient presents with fever, headache, and nuchal
rigidity. CSF analysis shows neutrophilic pleocytosis, low
glucose, and high protein. Which is the most likely pathogen?
A. Neisseria meningitidis
B. Listeria monocytogenes
C. Herpes simplex virus
D. Cryptococcus neoformans
Answer: A. Neisseria meningitidis
Rationale: Acute bacterial meningitis with neutrophilic CSF and
low glucose is most often caused by Neisseria in adults.
4. Which of the following is the preferred treatment for
uncomplicated cystitis in a non-pregnant adult woman?
A. Ciprofloxacin for 7 days
B. Nitrofurantoin for 5 days
C. Amoxicillin for 10 days
D. Trimethoprim for 14 days
Answer: B. Nitrofurantoin for 5 days
Rationale: Nitrofurantoin is first-line for uncomplicated urinary
tract infections, avoiding broad-spectrum antibiotics.
,5. A 50-year-old HIV-positive patient with CD4 count 50/mm³
presents with fever and weight loss. Blood cultures show
yeast-like organisms. Most likely pathogen?
A. Candida albicans
B. Histoplasma capsulatum
C. Cryptococcus neoformans
D. Aspergillus fumigatus
Answer: B. Histoplasma capsulatum
Rationale: Disseminated histoplasmosis is common in advanced
HIV with CD4 <100.
6. Which of the following antibiotics is contraindicated in
pregnancy?
A. Amoxicillin
B. Ceftriaxone
C. Tetracycline
D. Azithromycin
Answer: C. Tetracycline
Rationale: Tetracyclines can cause fetal teeth discoloration and
inhibit bone growth.
7. A 35-year-old man presents with fever, rash on palms and
soles, and lymphadenopathy. Rapid plasma reagin (RPR) test
is positive. Diagnosis?
A. Rocky Mountain spotted fever
, B. Secondary syphilis
C. Measles
D. Infectious mononucleosis
Answer: B. Secondary syphilis
Rationale: Palmar-plantar rash and positive RPR indicate
secondary syphilis.
8. A patient presents with watery diarrhea after recent
hospitalization and antibiotic therapy. Most likely causative
organism?
A. Escherichia coli
B. Salmonella enterica
C. Clostridioides difficile
D. Giardia lamblia
Answer: C. Clostridioides difficile
Rationale: C. difficile is associated with antibiotic use and
healthcare exposure.
9. Which of the following is the first-line therapy for
community-acquired MRSA skin infection?
A. Cephalexin
B. Clindamycin
C. Amoxicillin
D. Vancomycin IV
Questions WITH CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2026 Q&A |INSTANT
DOWNLOAD PDF
1. A 65-year-old man presents with fever, malaise, and cough.
He has a history of COPD and recently completed a course of
antibiotics. Chest X-ray shows a new infiltrate. Which
organism is most likely?
A. Streptococcus pneumoniae
B. Pseudomonas aeruginosa
C. Klebsiella pneumoniae
D. Haemophilus influenzae
Answer: B. Pseudomonas aeruginosa
Rationale: In patients with COPD and recent antibiotic exposure,
Pseudomonas is a common cause of hospital- or healthcare-
associated pneumonia.
2. Which of the following is the most sensitive test for latent
tuberculosis infection?
A. Tuberculin skin test (TST)
B. Chest X-ray
C. Interferon-gamma release assay (IGRA)
D. Sputum acid-fast bacilli smear
,Answer: C. Interferon-gamma release assay (IGRA)
Rationale: IGRA is more specific than TST, especially in patients
vaccinated with BCG.
3. A patient presents with fever, headache, and nuchal
rigidity. CSF analysis shows neutrophilic pleocytosis, low
glucose, and high protein. Which is the most likely pathogen?
A. Neisseria meningitidis
B. Listeria monocytogenes
C. Herpes simplex virus
D. Cryptococcus neoformans
Answer: A. Neisseria meningitidis
Rationale: Acute bacterial meningitis with neutrophilic CSF and
low glucose is most often caused by Neisseria in adults.
4. Which of the following is the preferred treatment for
uncomplicated cystitis in a non-pregnant adult woman?
A. Ciprofloxacin for 7 days
B. Nitrofurantoin for 5 days
C. Amoxicillin for 10 days
D. Trimethoprim for 14 days
Answer: B. Nitrofurantoin for 5 days
Rationale: Nitrofurantoin is first-line for uncomplicated urinary
tract infections, avoiding broad-spectrum antibiotics.
,5. A 50-year-old HIV-positive patient with CD4 count 50/mm³
presents with fever and weight loss. Blood cultures show
yeast-like organisms. Most likely pathogen?
A. Candida albicans
B. Histoplasma capsulatum
C. Cryptococcus neoformans
D. Aspergillus fumigatus
Answer: B. Histoplasma capsulatum
Rationale: Disseminated histoplasmosis is common in advanced
HIV with CD4 <100.
6. Which of the following antibiotics is contraindicated in
pregnancy?
A. Amoxicillin
B. Ceftriaxone
C. Tetracycline
D. Azithromycin
Answer: C. Tetracycline
Rationale: Tetracyclines can cause fetal teeth discoloration and
inhibit bone growth.
7. A 35-year-old man presents with fever, rash on palms and
soles, and lymphadenopathy. Rapid plasma reagin (RPR) test
is positive. Diagnosis?
A. Rocky Mountain spotted fever
, B. Secondary syphilis
C. Measles
D. Infectious mononucleosis
Answer: B. Secondary syphilis
Rationale: Palmar-plantar rash and positive RPR indicate
secondary syphilis.
8. A patient presents with watery diarrhea after recent
hospitalization and antibiotic therapy. Most likely causative
organism?
A. Escherichia coli
B. Salmonella enterica
C. Clostridioides difficile
D. Giardia lamblia
Answer: C. Clostridioides difficile
Rationale: C. difficile is associated with antibiotic use and
healthcare exposure.
9. Which of the following is the first-line therapy for
community-acquired MRSA skin infection?
A. Cephalexin
B. Clindamycin
C. Amoxicillin
D. Vancomycin IV
