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Appl. Environ. Microbiol., Dec 1996, 4314-4317, Vol 62, No. 12
K Rahn, JB Wilson, KA McFadden, SC Read, AG Ellis, SA Renwick, RC Clarke and RP Johnson
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.
Copyright © 1996, American Society for Microbiology
Comparison of Vero cell assay and PCR as indicators of the presence of verocytotoxigenic Escherichia coli in bovine and human fecal samples
Health of Animals Laboratory, Agriculture and Agri-Food Canada, Guelph, Ontario, Canada.
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