Daptomycin is used for MRSA and VRE infections. Its mechanism of action is fundamentally different from all beta-lactams and glycopeptides because it:
- A Inhibits D-alanyl-D-alanine ligase in peptidoglycan cross-linking
- B Inserts its lipid tail into the bacterial cell membrane forming oligomeric pores in a calcium-dependent manner, causing rapid membrane depolarization ✓
- C Irreversibly binds lipid II causing sequestration of peptidoglycan precursors
- D Inhibits the 30S ribosomal subunit preventing aminoacyl-tRNA binding
Correct answer: B. Inserts its lipid tail into the bacterial cell membrane forming oligomeric pores in a calcium-dependent manner, causing rapid membrane depolarization
Explanation
Daptomycin is a cyclic lipopeptide antibiotic. In the presence of physiological calcium ions, the drug's lipid tail inserts into the Gram-positive bacterial cytoplasmic membrane. Multiple daptomycin molecules oligomerize around a calcium ion, forming transient ion channels or membrane disruptions that cause rapid efflux of potassium ions and cell membrane depolarization. This kills bacteria rapidly without lysis. Daptomycin is inactivated by pulmonary surfactant, explaining why it CANNOT be used for pneumonia despite its MRSA coverage.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.