A poultry farm worker develops fever, headache, and patchy interstitial pneumonia. Sputum shows mononuclear infiltrate without bacteria on Gram stain. He keeps several sick parrots at home. Which organism is the most likely cause?
- A Coxiella burnetii
- B Chlamydia trachomatis serovar D
- C Chlamydophila psittaci ✓
- D Legionella pneumophila
Correct answer: C. Chlamydophila psittaci
Explanation
Psittacosis is atypical pneumonia caused by Chlamydophila psittaci, acquired by inhalation of aerosols from infected birds, classically parrots and other psittacine birds as well as poultry. The occupational and pet-bird exposure in the stem points directly to it. Legionella also causes atypical pneumonia but has no link to birds, and Coxiella is linked to livestock rather than psittacines.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.