title: Survival of antibiotic resistant and antibiotic sensitive strains of E. coli O157 and E. coli O26 in food matrices.
abstract: Escherichia coli O157:H7 or E. coli O26, which were AS (antibiotic sensitive), AR (laboratory created antibiotic resistant mutants), or naturally MAR (multi-antibiotic resistant), were inoculated into laboratory media, yoghurt or orange juice and their growth/survival monitored during enrichment at 37 degrees C or storage at 4 degrees C. The strains were also inoculated into minced beef and their thermal inactivation (D-values) examined at 55 degrees C, with and without a prior heat shock at 48 degrees C. The growth kinetics (lag phases, growth rates) of the VTEC (verocytotoxigenic E. coli), incubated over 24 h at 37 degrees C in laboratory media, were similar regardless of the presence or absence of antibiotic resistance. In yoghurt and orange juice, E. coli O157:H7 MAR died off significantly faster (P<0.05) than any of other VTEC strains examined. E. coli O157:H7 MAR was also found to be significantly more heat sensitive (P<0.05) than the other VTEC strains tested. The reasons for the observed differences in survival of the different VTEC strains and the link between antibiotic resistance and survival in VTEC organisms are discussed.
authors.affiliation: The National Food Centre, Teagasc, Ashtown, Dublin 15, Ireland. gduffy@nfc.teagasc.ie
authors.forename: G
authors.initials: G
authors.lastname: Duffy
authors.forename: C
authors.initials: C
authors.lastname: Walsh
authors.forename: I S
authors.initials: IS
authors.lastname: Blair
authors.forename: D A
authors.initials: DA
authors.lastname: McDowell
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001628:Beverages / Q000382:microbiology; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D024881:Drug Resistance, Bacterial; D024901:Drug Resistance, Multiple, Bacterial; D004926:Escherichia coli / Q000254:growth & development*; D019453:Escherichia coli O157 / Q000254:growth & development*; D005511:Food Handling / Q000379:methods*; D005516:Food Microbiology; D006801:Humans; D007700:Kinetics; D008461:Meat Products / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D013696:Temperature; D013997:Time Factors; D015014:Yogurt / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents