A 35-year-old healthcare worker develops community-acquired pneumonia with atypical features: dry cough, headache, myalgia and patchy infiltrate on CXR with cold agglutinins positive. The drug of choice for the likely causative organism is:
- A Amoxicillin
- B Ciprofloxacin
- C Ceftriaxone
- D Azithromycin (macrolide) ✓
Explanation
The clinical picture with cold agglutinins, atypical features and patchy infiltrate strongly suggests Mycoplasma pneumoniae infection — the classic cause of atypical (walking) pneumonia in young adults. Mycoplasma lacks a cell wall and is therefore intrinsically resistant to all beta-lactam antibiotics (amoxicillin, ceftriaxone) and vancomycin. Macrolides (azithromycin, clarithromycin) or doxycycline are drugs of choice because they inhibit protein synthesis without targeting cell wall. Fluoroquinolones (levofloxacin) are an alternative but not ciprofloxacin (poor activity against atypicals).
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.