A patient with a severe infection due to carbapenem-resistant Acinetobacter baumannii is treated with colistin. What is the mechanism of action of colistin?
- A Inhibits cell wall synthesis
- B Binds to lipopolysaccharide and disrupts outer membrane ✓
- C Inhibits protein synthesis at 30S
- D Inhibits DNA gyrase
Correct answer: B. Binds to lipopolysaccharide and disrupts outer membrane
Explanation
Colistin is a polymyxin that acts like a cationic detergent, binding to the lipid A component of lipopolysaccharide in the outer membrane of Gram-negative bacteria, causing leakage of cell contents. It does not inhibit cell wall synthesis or protein synthesis. Nephrotoxicity and neurotoxicity are dose-limiting.
Reference: Katzung: Basic & Clinical Pharmacology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.