An antimicrobial composition comprising at least two quaternary ammonium compounds selected from: (i) a quaternary ammonium compound having the formula: A4-nSi(R- NHaR1bZ)n and (ii) a quaternary ammonium compound having the formula: NHcR1dZ wherein in each of the at least two quaternary ammonium compounds A, R, R1, a, Z and n are independently selected, and: A is a member selected from the group consisting of alkoxy radicals, alkylether alkoxy radicals, and alkyl radicals； R is a divalent hydrocarbon radical； each R1 is independently a member selected from the group consisting of benzyl, alkyl radicals, alkyl ether hydrocarbon radicals, hydroxyl-containing alkyl radicals, and nitrogen-containing hydrocarbon radicals； Z is a member selected from the group consisting of chloride, bromide, iodide, tosylate, hydroxide, sulfate and phosphate； a is 0, 1 or 2, b is 1, 2 or 3, and the sum of a and b is 3； c is 0, 1, 2 or 3, d is 1, 2, 3 or 4, and the sum of c and d is 4； and n is 1, 2 or 3； and wherein the composition comprises at least two quaternary ammonium compounds of formula (i). A method of making an anti-microbial composition, and a method of reducing the number of micro-organisms on a surface, are disclosed.La présente invention concerne une composition antimicrobienne comprenant au moins deux composés d'ammonium quaternaire choisis parmi : (i) un composé d'ammonium quaternaire ayant la formule : A4-nSi(R-NHaR1bZ)n et (ii) un composé d'ammonium quaternaire ayant la formule : NHcR1dZ dans laquelle, dans chacun des au moins deux composés d'ammonium quaternaire, A, R, R1, a, Z et n sont indépendamment choisis, et : A est un membre choisi dans le groupe constitué de radicaux alcoxy, radicaux alkylétheralcoxy et radicaux alkyle ； R est un radical hydrocarboné divalent ； chaque R1 est indépendamment un élément choisi dans le groupe constitué de benzyle, radicaux alkyle, radicaux hydrocarbonés d'éther d'alkyle, radicaux alkyle contenant hydroxyle, et radicaux hydrocarboné
