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Appl. Environ. Microbiol., 04 1995, 1290-1293, Vol 61, No. 4
T Zhao, MP Doyle, J Shere and L Garber
The prevalence of Escherichia coli O157:H7 in dairy herds is poorly
understood, even though young dairy animals have been reported to be a
host. From February to May 1993, 662 fecal samples from 50 control herds in
14 states, and from June to August 1993, 303 fecal samples from 14 case
herds in 11 states were collected for isolation of E. coli O157:H7. Case
herds were those in which E. coli O157:H7 was isolated from preweaned
calves in a previous U.S. Department of Agriculture study, whereas control
herds from which E. coli O157:H7 had not been isolated previously were
randomly selected from the same states as case herds. Among the control
herds, E. coli O157:H7 was isolated from 6 of 399 calves (1.5%) that were
between 24 h old and the age of weaning and from 13 of 263 calves (4.9%)
that were between the ages of weaning and 4 months. Eleven of 50 control
herds (22%) were positive. Among the case herds, E. coli O157:H7 was
isolated from 5 of 171 calves (2.9%) that were between 24 h old and the age
of weaning and from 7 of 132 calves (5.3%) that were between the ages of
weaning and 4 months. Seven of 14 case herds (50%) were positive. Sixteen
of 31 isolates were obtained by direct plating, with populations ranging
from 10(3) to 10(5) CFU/g. Fifteen of 31 isolates were isolated by
enrichment only. Nineteen of the isolates produced both verocytotoxin 1
(VT-1) and VT-2, whereas 12 produced VT-2 only.
Copyright © 1995, American Society for Microbiology
Prevalence of enterohemorrhagic Escherichia coli O157:H7 in a survey of dairy herds
Center for Food Safety and Quality Enhancement, University of Georgia, Griffin 30223, USA.
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