Pneumonia USMLE Step 1 Practice Question
A 72-year-old man with a 15-year history of COPD (baseline FEVā 35% predicted) presents to the emergency department with a 3-day history of productive cough with purulent sputum, fever, and progressive dyspnea. His wife reports he has been increasingly short of breath despite his home oxygen therapy. Vital signs: temperature 39.1Ā°C, heart rate 115 bpm, respiratory rate 26/min, blood pressure 136/84 mmHg, oxygen saturation 86% on 2L nasal cannula. Physical examination reveals decreased breath sounds and crackles in the right lower lobe. Chest X-ray shows a new right lower lobe consolidation with associated pleural involvement. Gram stain of sputum demonstrates gram-negative rods. Sputum culture grows an organism that is oxidase-positive, motile, and produces a fruity odor. The patient denies recent hospitalization or antibiotic use. Which of the following organisms is most likely responsible for this community-acquired pneumonia?
Answer choices
- AStreptococcus pneumoniae
- BKlebsiella pneumoniae
- CHaemophilus influenzae
- DPseudomonas aeruginosaCorrect answer
- ELegionella pneumophila
- FProteus mirabilis
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