A 58-year-old diabetic man with MRSA bacteremia and concurrent hospital-acquired pneumonia is considered for daptomycin therapy. The microbiologist advises against it for the pulmonary component because:

• A Daptomycin is inactivated by pulmonary surfactant ✓
• B Pneumonic tissue has a pH that renders daptomycin bacteriostatic
• C Daptomycin cannot penetrate consolidated lung parenchyma
• D Alveolar macrophages rapidly metabolize daptomycin

Explanation

Daptomycin binds pulmonary surfactant and its activity is antagonized in alveolar lining fluid, so it achieves poor efficacy in pneumonia despite adequate penetration. It is approved for complicated skin infections, right-sided endocarditis and bacteremia but explicitly not for pneumonia. Vancomycin or linezolid is preferred for MRSA pneumonia. The drug remains fully bactericidal elsewhere in the body, and tissue penetration or macrophage metabolism plays no role in this failure pattern.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.