Colistin (Polymyxin E)
Overview
Colistin, also known as polymyxin E, is a cyclic polypeptide antibiotic structurally similar to polymyxin B, produced by Paenibacillus polymyxa. It disrupts the bacterial cell membrane by binding to lipopolysaccharide and displacing divalent cations, leading to increased permeability and cell lysis. The compound is administered as colistimethate sodium, an inactive prodrug that is hydrolyzed in vivo to the active colistin base. Its spectrum targets Gram-negative bacteria, particularly Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae.
Key Research Findings
Colistin was FDA approved in 1962 but fell out of favor due to nephrotoxicity; it has been reintroduced as a last-resort therapy for multidrug-resistant Gram-negative infections. Clinical trials and retrospective cohort studies have documented efficacy in ventilator-associated pneumonia and bloodstream infections caused by carbapenem-resistant organisms. Emergence of colistin resistance mediated by the plasmid-borne mcr-1 gene has been reported worldwide, raising concerns about its long-term utility.
Intravenous, Intramuscular, Inhalation
FDA Approved
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