title: Development of a method for the detection of verotoxin-producing Escherichia coli in food.
abstract: The growing recognition of the role of non-O157 verotoxigenic Escherichia coli (VTEC) in foodborne illness underscores the importance of developing methods to detect it in the food supply. We describe here the development of a protocol for the detection, isolation, and characterization  of VTEC from foods, designed for the serotype-independent enrichment, detection, and isolation of VTEC, in combination with rapid characterization of VTEC O157, O26, O103, O111, and O145. This study examined the inhibitory concentration of six antimicrobial agents used either singly or in  combination for the optimal enrichment of a panel of 18 different O serogroups of VTEC in modified tryptic soy broth. Considerable variability in resistance to the different antimicrobials tested was noted among different VTEC strains. The combination enabling growth of strains of all 18 different  O serogroups was vancomycin (10 μg/ml) and cefsulodin (3 μg/ml). A similar combination of antimicrobials formulated in agar plates was found beneficial in the recovery of VTEC strains from enrichment broth cultures. The efficacy of these media in the recovery of selected VTEC (O26, O103,  O111, O145, and O157) from ground beef and O157 VTEC from lettuce, spinach, and apple cider was demonstrated. The selective enrichment media described herein would appear suitable for incorporation in methods for the recovery and detection of a wide range of VTEC serogroups.
authors.affiliation: Health Canada, Bureau of Microbial Hazards, 251 Sir Frederick Banting Driveway, P.L. 2204E Ottawa, Ontario, Canada K1A 0K9. alex.gill@hc-sc.gc.ca
authors.forename: Alexander
authors.initials: A
authors.lastname: Gill
authors.forename: Amalia
authors.initials: A
authors.lastname: Martinez-Perez
authors.forename: Sarah
authors.initials: S
authors.lastname: McIlwham
authors.forename: Burton
authors.initials: B
authors.lastname: Blais
mesh_terms: D000362:Agar; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015169:Colony Count, Microbial / Q000379:methods*; D003257:Consumer Product Safety; D003470:Culture Media; D024881:Drug Resistance, Bacterial; D005506:Food Contamination / Q000032:analysis*; D005516:Food Microbiology; D006801:Humans; D012703:Serotyping; D022603:Shiga Toxins / Q000096:biosynthesis; D054323:Shiga-Toxigenic Escherichia coli / Q000145:classification* / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media; D022603:Shiga Toxins; D000362:Agar