title: Prevalence of the eaeA gene in verotoxigenic Escherichia coli strains from dairy cattle in Southwest Ontario.
abstract: This study determined the prevalence of the eaeA gene and its relationship to serotype and type of verotoxin produced in a collection of 432 verotoxigenic Escherichia coli (VTEC) obtained from the faeces of healthy cows and calves in a systematic random survey involving 80 dairy farms in Southwest Ontario. A PCR amplification procedure involving primer pairs which target the conserved central region of the O157:H7 eaeA gene showed that 151 (35.2%) strains were positive for the eaeA gene. All isolates (9-21 for each O group) of O groups 5, 26, 69, 84, 103, 111, 145 and 157 were positive, whereas all isolates (7-34 for each O group) of O groups 113, 132, and 153 and serotype O156:NM (38 isolates) were negative for eaeA. Seventy-three percent of 130 isolates of eaeA-positive serotypes produced VT1 only compared with 20% of 253 isolates of eaeA-negative serotypes. We conclude that there is a strong association between certain O groups and the eaeA gene, that serotypes of eaeA-positive and eaeA-negative VTEC implicated in human and cattle disease are present at high frequency in the faeces of healthy cattle, that VT1 is more frequently associated with eaeA-positive than with eaeA-negative serogroups, and that the eaeA gene is more frequently found in VTEC from calves compared with VTEC from adult cattle.
authors.affiliation: Ontario Veterinary College, University of Guelph, Canada.
authors.forename: K S
authors.initials: KS
authors.lastname: Sandhu
authors.forename: R C
authors.initials: RC
authors.lastname: Clarke
authors.forename: K
authors.initials: K
authors.lastname: McFadden
authors.forename: A
authors.initials: A
authors.lastname: Brouwer
authors.forename: M
authors.initials: M
authors.lastname: Louie
authors.forename: J
authors.initials: J
authors.lastname: Wilson
authors.forename: H
authors.initials: H
authors.lastname: Lior
authors.forename: C L
authors.initials: CL
authors.lastname: Gyles
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000378:metabolism*; D001483:Base Sequence; D002417:Cattle / Q000382:microbiology*; D004926:Escherichia coli / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D005243:Feces / Q000382:microbiology; D005260:Female; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D022622:Shiga Toxin 1
chemical_list: D001427:Bacterial Toxins; D022622:Shiga Toxin 1