colistin B

Colistin B, also known as Polymyxin E2, is a cyclic polypeptide antibiotic and one of the two major active components of colistin (Polymyxin E), alongside colistin A (Polymyxin E1). It belongs to the polymyxin class of antibiotics, which are considered last-resort treatments for multidrug-resistant Gram-negative bacterial infections. Colistin B exerts its bactericidal effect by disrupting the integrity of bacterial cell membranes. It primarily targets the lipopolysaccharide (LPS) layer of Gram-negative bacteria, where its cationic nature allows it to bind to negatively charged phosphate groups, displacing essential divalent cations like magnesium and calcium. This destabilizes the outer membrane, increasing its permeability. Subsequently, colistin B interacts with the inner cytoplasmic membrane, intercalating into the phospholipid bilayer and causing leakage of intracellular components, leading to bacterial cell death. Colistin was discovered in 1947 and is derived from the bacterium Paenibacillus polymyxa subspecies colistinus.

Other names

Polymyxin E2