Bacterial Infections USMLE Step 1 Practice Question
A 5-week-old male infant presents with staccato cough and tachypnea for 2 weeks. Vital signs show HR 160 bpm, RR 52/min, BP 85/55 mmHg, temp 37.2°C, SpO2 88% on room air. He feeds well without vomiting. Bilateral conjunctival injection is noted; fever is absent. Chest radiograph demonstrates hyperinflation with diffuse bilateral interstitial infiltrates. Serum IgM is elevated. Which organism most likely caused this pneumonia?
Answer choices
- ALegionella pneumophila
- BRespiratory syncytial virus
- CBordetella pertussis
- DChlamydia trachomatisCorrect answer
- EGroup B Streptococcus
- FStreptococcus pneumoniae
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