Internal Medicine Exam Common Infectious Diseases 2 — Questions and Answers
Question 1: A 28-year-old woman presents with dysuria, frequency, and suprapubic pain for 2 days. Urinalysis shows pyuria and bacteriuria. What is the most appropriate initial treatment?
- Nitrofurantoin for 5 days (Correct answer)
- Ciprofloxacin for 14 days
- Amoxicillin for 3 days
- Trimethoprim-sulfamethoxazole for 10 days
Correct answer: Nitrofurantoin for 5 days
Nitrofurantoin for 5 days is first-line therapy for uncomplicated UTI in non-pregnant women due to efficacy and low resistance rates.
Question 2: Which organism is the most common cause of community-acquired pneumonia in otherwise healthy adults under 60?
- Streptococcus pneumoniae (Correct answer)
- Haemophilus influenzae
- Mycoplasma pneumoniae
- Klebsiella pneumoniae
Correct answer: Streptococcus pneumoniae
Streptococcus pneumoniae is the most common bacterial cause of community-acquired pneumonia across all age groups.
Question 3: A patient returns from a trip to sub-Saharan Africa with cyclic fevers, chills, and headache. Thick and thin blood smears are ordered. Which Plasmodium species causes the most severe and potentially fatal malaria?
- Plasmodium vivax
- Plasmodium ovale
- Plasmodium falciparum (Correct answer)
- Plasmodium malariae
Correct answer: Plasmodium falciparum
Plasmodium falciparum causes the most severe malaria, with complications including cerebral malaria, severe anemia, and multi-organ failure.
Question 4: A 35-year-old male presents with painless genital ulcer and inguinal lymphadenopathy. VDRL is reactive. Which antibiotic is first-line treatment?
- Azithromycin 1g single dose
- Benzathine penicillin G 2.4 million units IM (Correct answer)
- Doxycycline 100mg twice daily for 14 days
- Ceftriaxone 250mg IM single dose
Correct answer: Benzathine penicillin G 2.4 million units IM
Benzathine penicillin G 2.4 million units IM single dose is the standard first-line treatment for primary and secondary syphilis.
Question 5: Which finding best distinguishes bacterial meningitis from viral meningitis on CSF analysis?
- Elevated opening pressure
- Glucose less than 45 mg/dL with high protein (Correct answer)
- Lymphocytic pleocytosis
- Xanthochromia
Correct answer: Glucose less than 45 mg/dL with high protein
Low CSF glucose (<45 mg/dL) combined with markedly elevated protein is characteristic of bacterial meningitis, reflecting bacterial consumption of glucose.
Question 6: A 60-year-old patient with COPD develops productive cough with purulent sputum and fever. Sputum Gram stain shows gram-negative coccobacilli. Which organism is most likely?
- Pseudomonas aeruginosa
- Moraxella catarrhalis
- Haemophilus influenzae (Correct answer)
- Klebsiella pneumoniae
Correct answer: Haemophilus influenzae
Haemophilus influenzae is the most common gram-negative coccobacillus causing acute exacerbations of COPD.
Question 7: A patient with HIV and CD4 count of 50 cells/μL presents with headache, fever, and neck stiffness. India ink stain of CSF shows encapsulated yeast. What is the treatment of choice?
- Fluconazole 400mg daily
- Amphotericin B plus flucytosine (Correct answer)
- Voriconazole IV
- Micafungin IV
Correct answer: Amphotericin B plus flucytosine
Induction therapy for cryptococcal meningitis consists of amphotericin B plus flucytosine for at least 2 weeks, followed by fluconazole consolidation.
