Pneumonia USMLE Step 1 Practice Question

A 28-year-old previously healthy woman presents to the emergency department with a 5-day history of fever (39.2°C), nonproductive cough, headache, myalgias, and malaise. She works part-time at a pet store and recalls handling parrots and budgies 1 week prior to symptom onset. Vital signs: HR 102 bpm, BP 118/76 mmHg, RR 22/min, SpO2 98% on room air. Physical examination reveals mild hypoxia on exertion. Chest X-ray shows bilateral interstitial infiltrates with a basilar predominance. Laboratory results: WBC 8,200/μL (normal differential), hyponatremia (Na+ 125 mEq/L), ALT 78 U/L, AST 92 U/L, procalcitonin 0.8 ng/mL (normal <0.5), normal urinalysis. She denies recent travel outside the city, recent antibiotic use, and has no sick contacts. Which of the following organisms is most likely responsible for this patient's pneumonia?