Internal Medicine Exam Community-Acquired Pneumonia 2 — Questions and Answers
Question 1: A 68-year-old nursing home resident develops fever, productive cough, and lobar consolidation on CXR. Which pathogen is MOST likely responsible?
- Mycoplasma pneumoniae
- Streptococcus pneumoniae (Correct answer)
- Legionella pneumophila
- Chlamydophila pneumoniae
Correct answer: Streptococcus pneumoniae
S. pneumoniae remains the most common cause of CAP in elderly and nursing home residents, producing classic lobar consolidation.
Question 2: Which scoring system is preferred in the ED to determine ICU admission criteria for CAP?
- PSI/PORT score
- CURB-65
- IDSA/ATS minor criteria (Correct answer)
- APACHE II
Correct answer: IDSA/ATS minor criteria
IDSA/ATS minor criteria (≥3 of 9) best identify patients requiring ICU-level care, including vasopressors or mechanical ventilation.
Question 3: A 45-year-old with CAP has Na 128, BUN 28, RR 26, BP 88/60, age <65. What is his CURB-65 score?
Correct answer: 4
CURB-65 assigns 1 point each for confusion, urea >7 (BUN ≥19 mg/dL), RR ≥30, BP <90/60, and age ≥65; this patient scores 4 (BUN, RR, BP, confusion not mentioned but Na—confusion not stated, so BUN+RR+BP = 3).
Question 4: Which antibiotic combination is recommended for severe CAP requiring ICU admission in a patient with no Pseudomonas risk factors?
- Azithromycin monotherapy
- Amoxicillin-clavulanate + doxycycline
- Beta-lactam + macrolide or respiratory fluoroquinolone (Correct answer)
- Vancomycin + piperacillin-tazobactam
Correct answer: Beta-lactam + macrolide or respiratory fluoroquinolone
IDSA/ATS guidelines recommend a beta-lactam combined with either a macrolide or respiratory fluoroquinolone for severe CAP without Pseudomonas risk.
Question 5: A patient with CAP is found to have a parapneumonic effusion. What finding on thoracentesis most clearly indicates need for chest tube drainage?
- pH 7.25, glucose 55 mg/dL, LDH 800 U/L (Correct answer)
- pH 7.30, glucose 70 mg/dL, LDH 500 U/L
- pH 7.35, glucose 80 mg/dL, LDH 200 U/L
- pH 7.40, glucose 90 mg/dL, LDH 150 U/L
Correct answer: pH 7.25, glucose 55 mg/dL, LDH 800 U/L
A complicated parapneumonic effusion with pH <7.20, glucose <60, or LDH >1000 (or positive Gram stain/culture) requires drainage.
Question 6: Which organism should be specifically covered when CAP is associated with recent influenza infection?
- Legionella pneumophila
- Staphylococcus aureus (including MRSA) (Correct answer)
- Moraxella catarrhalis
- Klebsiella pneumoniae
Correct answer: Staphylococcus aureus (including MRSA)
Post-influenza bacterial pneumonia most commonly involves S. aureus (including community-acquired MRSA), which requires targeted coverage.
Question 7: A 60-year-old with CAP is started on levofloxacin. On day 3, he remains febrile with worsening infiltrates. What is the most appropriate next step?
- Add vancomycin empirically
- Broaden to meropenem
- Perform CT chest and bronchoscopy with BAL (Correct answer)
- Switch to azithromycin monotherapy
Correct answer: Perform CT chest and bronchoscopy with BAL
Failure to improve by 72 hours warrants diagnostic workup including CT chest and bronchoscopy to identify resistant pathogens, alternative diagnoses, or complications.
