title: Enterohemorrhagic Escherichia coli colony check assay for the identification of serogroups O26, O45, O103, O111, O121, O145, and O157 colonies isolated on plating media.
abstract: A simple immunoenzymatic enterohemorrhagic Escherichia coli (EHEC) colony check (ECC) assay was developed for the presumptive identification of priority EHEC colonies isolated on plating media from enrichment broth cultures of foods. With this approach, lipopolysaccharide extracted from a colony is spotted on the grid of a polymyxin-coated polyester cloth strip, and bound E. coli serogroup O26, O45, O103, O111, O121, O145, and O157 antigens are subsequently detected by sequential reactions with a pool of commercially available peroxidase-conjugated goat antibodies and tetramethylbenzidine substrate solution. Each strip can accommodate up to 15 colonies, and test results are available within 30 min. Assay performance was verified using colonies from a total of 73 target EHEC isolates covering the range of designated priority serogroups (all of which were reactive), 41 nontarget E. coli isolates including several nontarget Shiga toxin-producing E. coli serogroups (all unreactive), and 33 non-E. coli strains (all unreactive except two bacterial strains possessing O-antigenic structures in common with those of the priority EHEC). The ECC assay was reactive with target colonies grown on several types of selective and nonselective plating media designed for their cultivation. These results support the use of the ECC assay for high-throughput screening of colonies isolated on plating media for detecting priority EHEC strains in foods.
authors.affiliation: Ontario Laboratory Network, Canadian Food Inspection Agency, 960 Carling Avenue, Building 22, Central Experimental Farm, Ottawa, Ontario, Canada K1A 0C6. burton.blais@inspection.gc.ca.
authors.forename: Burton
authors.initials: B
authors.lastname: Blais
authors.affiliation: Ontario Laboratory Network, Canadian Food Inspection Agency, 960 Carling Avenue, Building 22, Central Experimental Farm, Ottawa, Ontario, Canada K1A 0C6.
authors.forename: Mylène
authors.initials: M
authors.lastname: Deschênes
authors.affiliation: Ontario Laboratory Network, Canadian Food Inspection Agency, 960 Carling Avenue, Building 22, Central Experimental Farm, Ottawa, Ontario, Canada K1A 0C6.
authors.forename: George
authors.initials: G
authors.lastname: Huszczynski
authors.affiliation: Ontario Laboratory Network, Canadian Food Inspection Agency, 960 Carling Avenue, Building 22, Central Experimental Farm, Ottawa, Ontario, Canada K1A 0C6.
authors.forename: Martine
authors.initials: M
authors.lastname: Gauthier
mesh_terms: D000818:Animals; D002417:Cattle; D015169:Colony Count, Microbial / Q000295:instrumentation / Q000379:methods*; D003470:Culture Media / Q000378:metabolism*; D054324:Enterohemorrhagic Escherichia coli / Q000145:classification / Q000235:genetics / Q000254:growth & development* / Q000302:isolation & purification; D004926:Escherichia coli / Q000145:classification / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification; D008460:Meat / Q000382:microbiology*; D012703:Serotyping
chemical_list: D003470:Culture Media