A 45-year-old diabetic patient is admitted with a foot infection caused by MRSA. The decision to use daptomycin is made. Daptomycin's mechanism of action is unique among antibiotics. Which statement accurately describes it?
- A It inserts into bacterial cell membranes in a calcium-dependent manner, causing depolarisation and ion leakage ✓
- B It inhibits the 50S ribosomal subunit by binding to the peptidyl transferase centre
- C It inhibits transpeptidation of peptidoglycan cross-links by binding penicillin-binding proteins
- D It blocks lipopolysaccharide assembly in the outer membrane of gram-negative bacteria
Correct answer: A. It inserts into bacterial cell membranes in a calcium-dependent manner, causing depolarisation and ion leakage
Explanation
Daptomycin is a lipopeptide antibiotic that binds to the gram-positive bacterial cell membrane in the presence of calcium, forms oligomeric pores, and causes rapid depolarisation with potassium efflux, leading to cell death. It is not effective against gram-negative organisms because their outer membrane prevents access. It does not act on ribosomes or cell wall synthesis. Daptomycin is inactivated by pulmonary surfactant and cannot be used for pneumonia.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.