Pneumonia USMLE Step 1 Practice Question
A 72-year-old man with COPD presents with 3 days of productive cough, fever to 38.5°C, and dyspnea. Chest X-ray shows a left lower lobe consolidation. Sputum culture grows gram-negative rods that ferment lactose. Blood cultures remain negative after 48 hours. Which of the following is the most likely causative organism?
Answer choices
- ALegionella pneumophila
- BPseudomonas aeruginosa
- CStreptococcus pneumoniae
- DKlebsiella pneumoniaeCorrect answer
- EMycoplasma pneumoniae
- FHaemophilus influenzae
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