A 20-year-old student presents with dry cough, low-grade fever and malaise; chest radiograph shows patchy perihilar infiltrates out of proportion to sparse auscultatory findings. Cold agglutinins are positive. Which antibiotic class provides empirical coverage of the most likely pathogen?

• A Aminoglycosides, because they are bactericidal against Gram-negative rods
• B Macrolides, because they act on the 50S ribosome of organisms lacking a cell wall ✓
• C Cephalosporins, because they inhibit peptidoglycan cross-linking
• D Metronidazole, because it reaches high respiratory tissue concentrations

Explanation

The picture suggests Mycoplasma pneumoniae pneumonia, an organism without a cell wall, making it inherently resistant to all beta-lactams and insensitive to aminoglycoside cell-entry logic. Macrolides inhibit protein synthesis on the 50S subunit and are standard therapy for Mycoplasma, Legionella and Chlamydophila respiratory infections. Metronidazole has no role since it requires anaerobic activation and lacks activity against these aerobes.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.