Polymyxin B (PmB)

Polymyxin B is an antibiotic primarily used for resistant gram negative infections. Polymyxins bind to the cell membrane and alter its structure making it more permeable. The resulting water uptake leads to cell death. They are cationic, basic proteins that act like detergents (surfactants). Side effects include neurotoxicity and acute renal tubular necrosis. It is commonly used in the topical first aid preparation Neosporin. Polymyxins are antibiotics, with a general structure consisting of a cyclic peptide with a long hydrophobic tail. They disrupt the structure of the bacterial cell membrane by interacting with its phospholipids. They are produced by the Gram-positive bacterium Bacillus polymyxa and are selectively toxic for Gram-negative bacteria due to their specificity for the lipopolysaccharide molecule that exists within many Gram-negative outer membranes.