NCIt definition : The sodium salt of colistimethate, a broad-spectrum polymyxin antibiotic against most
aerobic Gram-negative bacteria except Proteus bacteria. Colistimethate sodium contains
the pentasodium salt of the penta(methanesulfonic acid) derivative of colistin A as
the major component and a small proportion of the petasodium salt of the pentamethanesulfonate
derivative of colistin B. Colistins are cyclic polypeptides produced from Bacillus
colistinus or B. polymyxa and function as a surfactant which penetrates into and disrupts
the bacterial cell membrane, thereby resulting in bactericidal effect.;