What is "polymyxin b"

Polymyxin B is an antibiotic primarily used for resistant Gram-negative infections. It is derived from the bacterium Bacillus polymyxa. Polymyxin B is composed of a number of related compounds (see "Mixture composition"). It has a bactericidal action against almost all Gram-negative bacilli except the Proteus and Neisseria genera. Polymyxins bind to the cell membrane and alter its structure, making it more permeable. The resulting water uptake leads to cell death. Polymyxins are cationic, basic peptides that act like detergents ( surfactants). Side effects include neurotoxicity and acute renal tubular necrosis. Polymyxins are used in the topical first-aid preparation Neosporin.

1. Family of polypeptides with attached fatty acid; cationic detergent at physiological pH, both hydrophilic and hydrophobic properties
2. Bactericidal for gram-negative; little to no effect on gram-positive, since cell wall is too thick to permit access to membrane