Which of the following statements correctly describes the antibacterial mechanism of colistin?

• A It inhibits the 50S ribosomal subunit and blocks peptide bond formation
• B It inhibits DNA-dependent RNA polymerase by binding the beta subunit
• C It binds lipid A of lipopolysaccharide and disrupts the outer bacterial membrane in a detergent-like manner ✓
• D It forms a ternary complex with EF-G and stalls ribosomal translocation

Explanation

Colistin is a cationic cyclic polypeptide that electrostatically binds to the negatively charged lipid A component of lipopolysaccharide in the outer membrane of gram-negative bacteria, displacing magnesium ions and disrupting membrane integrity in a detergent-like fashion, causing leakage of cell contents. Ribosomal 50S inhibition describes macrolides and chloramphenicol, RNA polymerase inhibition describes rifampicin, and the EF-G translocation block describes fusidic acid. Its dose limiting toxicities are nephrotoxicity and neuromuscular blockade.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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