title: Comparison of Vero cell assay and PCR as indicators of the presence of verocytotoxigenic Escherichia coli in bovine and human fecal samples.
abstract: Comparisons were made between Vero cell assay (VCA) and PCR as indicators for the detection of verocytotoxigenic Escherichia coli (VTEC; also known as Shiga-like toxin-producing E. coli) and as predictors of VTEC isolation from bovine and human fecal samples. Fecal samples were collected as part of a survey on the prevalence of VTEC on dairy farms in southern Ontario (J. B. Wilson et al., J. Infect. Dis., 174:1021-1027, 1996). A total of 2,655 samples were examined by VCA and PCR, 2,153 originating from cattle and 502 originating from humans. Overall, 36.2% of the samples were positive in the VCA and 38.7% were positive by PCR. Of the VCA-positive samples screened, 41.6% yielded a VTEC isolate. For both human and bovine samples, a significant positive association between PCR result and VCA titer (P = 0.0001) was found. In addition, there was a significant positive association between the PCR result and VTEC isolation from VCA-positive samples for cattle (odds ratio = 9.1, P < 0.0001). For bovine samples positive in the VCA, VCA titer was significantly associated with the probability of obtaining a VTEC isolate. Agreement between VCA and PCR was good for both bovine and human samples (kappa = 0.69 and 0.64, respectively). The sensitivity and specificity of the PCR with respect to the VCA for bovine samples were 82.0 and 86.5%, respectively, and those for human samples were 59.3 and 98.1%, respectively. Although correlation between VCA and PCR results was not absolute, when used in conjunction, these tests complemented one another as predictors of VTEC isolation.
authors.affiliation: Health of Animals Laboratory, Agriculture and Agri-Food Canada, Guelph, Ontario, Canada.
authors.forename: K
authors.initials: K
authors.lastname: Rahn
authors.forename: J B
authors.initials: JB
authors.lastname: Wilson
authors.forename: K A
authors.initials: KA
authors.lastname: McFadden
authors.forename: S C
authors.initials: SC
authors.lastname: Read
authors.forename: A G
authors.initials: AG
authors.lastname: Ellis
authors.forename: S A
authors.initials: SA
authors.lastname: Renwick
authors.forename: R C
authors.initials: RC
authors.lastname: Clarke
authors.forename: R P
authors.initials: RP
authors.lastname: Johnson
mesh_terms: D000818:Animals; D002417:Cattle; D002522:Chlorocebus aethiops; D004926:Escherichia coli / Q000302:isolation & purification* / Q000472:pathogenicity; D005243:Feces / Q000382:microbiology*; D006801:Humans; D016133:Polymerase Chain Reaction; D014709:Vero Cells