title: Distribution and characteristics of verocytotoxigenic Escherichia coli isolated from Ontario dairy cattle.
abstract: Faecal swabs obtained from a random sample of 1131 cows and 659 calves on 100 southern Ontario dairy farms were examined for verocytotoxigenic Escherichia coli (VTEC) using a Vero cell assay. Five isolates from each positive culture were tested similarly. Positive colonies were examined with DNA probes for Shiga-like toxin I (SLT-I) and SLT-II sequences. Probe-negative colonies were tested for neutralization of verocytotoxicity using anti-SLT-I and anti-SLT-IIv antisera. Colonies showing no neutralization response were examined in a polymerase chain reaction procedure. Colonies positive by any test were confirmed to be E. coli biochemically, serotyped, biotyped and tested for antimicrobial resistance. Faecal culture supernatants which were positive in the Vero cell assay, but culture negative, were examined using the neutralization assay. Animals were classified positive by faecal culture supernatant or by positive VTEC isolate. The prevalence rates of VTEC infection in cows and calves were estimated to be 9.5 and 24.7%, respectively. The proportion of animals infected on each farm ranged from 0 to 60% for cows and 0 to 100% for calves. Of 206 VTEC isolates identified, few were of serotypes which have been isolated from humans and none were E. coli O 157.H7.
authors.affiliation: Department of Population Medicine, Ontario Veterinary College, University of Guelph, Canada.
authors.forename: J B
authors.initials: JB
authors.lastname: Wilson
authors.forename: S A
authors.initials: SA
authors.lastname: McEwen
authors.forename: R C
authors.initials: RC
authors.lastname: Clarke
authors.forename: K E
authors.initials: KE
authors.lastname: Leslie
authors.forename: R A
authors.initials: RA
authors.lastname: Wilson
authors.forename: D
authors.initials: D
authors.lastname: Waltner-Toews
authors.forename: C L
authors.initials: CL
authors.lastname: Gyles
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000032:analysis* / Q000235:genetics; D002417:Cattle; D002418:Cattle Diseases / Q000145:classification / Q000382:microbiology*; D003603:Cytotoxins / Q000032:analysis / Q000235:genetics; D015342:DNA Probes; D004768:Enterotoxins / Q000032:analysis / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D005243:Feces / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D008828:Microbiological Techniques / Q000662:veterinary; D009864:Ontario; D016133:Polymerase Chain Reaction; D015995:Prevalence; D011897:Random Allocation; D012703:Serotyping; D022622:Shiga Toxin 1; D014709:Vero Cells
chemical_list: D001427:Bacterial Toxins; D003603:Cytotoxins; D015342:DNA Probes; D004768:Enterotoxins; D022622:Shiga Toxin 1