Pneumonia USMLE Step 1 Practice Question
A 72-year-old man with COPD presents with acute dyspnea and productive cough with rusty sputum. Vital signs show temperature 39.2°C, heart rate 108/min, blood pressure 142/88 mmHg, respiratory rate 24/min, and SpO2 88% on room air. Chest X-ray demonstrates lobar consolidation in the right lower lobe. Laboratory studies reveal WBC 14,200/μL; blood cultures pending. He denies recent antibiotic use. Which organism is most likely responsible for this pneumonia?
Answer choices
- AMycoplasma pneumoniae
- BHaemophilus influenzae
- CLegionella pneumophila
- DPseudomonas aeruginosa
- EStreptococcus pneumoniaeCorrect answer
- FMoraxella catarrhalis
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.