Polymyxin E — a last-resort agent whose plasmid-borne mcr-1 resistance gene raised global alarm.
Also known as: polymyxin E · colistimethate (prodrug)
Part of the Foundational & therapeutic peptides cluster
Overview
Colistin, also called polymyxin E, is a cyclic lipopeptide antibiotic from Paenibacillus species and a close relative of polymyxin B. It displaces divalent cations from lipopolysaccharide phosphate groups, breaking down the Gram-negative outer membrane. Classified by the WHO as critically important and reserved as a last-resort drug, its usefulness is threatened by the mobile mcr-1 resistance gene. This page is educational and not medical advice.
Source & context
Biological / chemical source: Bacteria of the genus Paenibacillus (Paenibacillus polymyxa)
Primary research or clinical context: Last-resort approved antibiotic for multidrug-resistant Gram-negative infections
How it works
Like polymyxin B, colistin is a polycationic cyclic lipopeptide rich in diaminobutyric acid. It competitively displaces Ca2+ and Mg2+ that bridge neighboring lipopolysaccharide molecules, destabilizing the outer membrane and causing leakage and death of Gram-negative bacteria. It is administered as the less-toxic prodrug colistimethate sodium.
Resistance concern
Discovered in 1947, colistin was sidelined by toxicity, then revived against carbapenem-resistant organisms. The 2015 discovery of the plasmid-borne mcr-1 gene, which spreads colistin resistance between bacteria, made stewardship of this last-resort drug a major public-health topic.
FAQ about Colistin
What is Colistin?+
Colistin, also called polymyxin E, is a cyclic lipopeptide antibiotic from Paenibacillus species and a close relative of polymyxin B. It displaces divalent cations from lipopolysaccharide phosphate groups, breaking down the Gram-negative outer membrane. Classified by the WHO as critically important and reserved as a last-resort drug, its usefulness is threatened by the mobile mcr-1 resistance gene. This page is educational and not medical advice.
Is Colistin an approved medicine?+
Colistin: Last-resort approved antibiotic for multidrug-resistant Gram-negative infections. Always follow licensed medical guidance for approved products.
What is the typical length of Colistin?+
Colistin is not a classic amino-acid chain peptide in the same sense; see the profile for classification details.