Disclosed herein is a composition comprising at least one polymyxin or a salt thereof represented by formula (I) wherein R1 is an aliphatic linear or branched C6-C10 acyl group, or (I) R5 is -CH(CH3)2, -CH2CH(CH3)2, -CH(CH3)CH2CH3, or -CH2C6H5 R6 is -CH(CH3)2, -CH2CH(CH3)2, or -CH(CH3)CH2CH3 each of R2, R3, R4, R7and R8 is either -(CH2)XCH2NH2 or -(CH2)xCH2N(CH2SO3M)2 wherein x is 0 or 1 wherein M is a monovalent cation and wherein at least three of R2, R3, R4, R7and R8 are -(CH2)xCH2N(CH2SO3M)2.De describe una composición que comprende cuando menos una polimixina o una sal de ésta representada por la fórmula (I). (ver Fórmula) en donde: R1 es un grupo acilo C6-C10 alifático, ramificado o lineal, o (ver Fórmula) R5 es -CH(CH3)2, -CH2CH(CH3)2, -CH(CH3)CH2CH3, o -CH2C6H5 R6 es -CH(CH3)2, -CH2CH(CH3)2, o -CH(CH3)CH2CH3 cada uno de R2,R3,R4, R7 y R8 es ya sea -(CH2)XCH2NH2 o - (CH2)XCH2N(CH2SO3M)2 en donde x es 0 o 1en donde M es un catión monovalente y en donde cuando menos tres de R2,R3,R4,R7 y R8 son -(CH2)XCH2N(CH2SO3M)2.
