Antimicrobial Effect of Chemical Preservatives on Enterohemorrhagic Escherichia coli O157:H7.

Abstract

Three strains of enterohemorrhagic Escherichia coli O157 : H7 derived from patients of outbreaks in Osaka, Japan 1996 were used to determine the antimicrobial effect of the chemical preservatives : sorbic acid, benzoic acid, p-hydroxybenzoic acid, and dehydroacetic acid. The pH of the media strictly limited the growth of the pathogenic strains; a pH of 5.5 or below completely inhibited growth of these strains. The minimum inhibitory concentration (MIC) value for sorbic acid, benzoic acid, and dehydroacetic acid was 4mg/ml and that of p-hydroxybenzoic acid was 16mg/ml for the three pathogenic strains. Under the MIC conditions, the action of sorbic acid was bactericidal, whereas the other three antimicrobial chemicals were bacteriostatic. In Japan, the maximum allowable dose level of sorbic acid in meat products is 2mg/g, which corresponds to half the MIC concentration. To determine if this concentration resulted in an antimicrobial effect, homogenized hamburger beef was experimentally contaminated with E. coli O157 : H7 at an initial level of 104 colony forming unit/g. After incubation for 7 days, this concentration of sorbic acid demonstrated a bacteriostatic effect in the meat.