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Applied and Environmental Microbiology, April 2001, p. 1619-1627, Vol. 67, No. 4
Food Animal Health and Management Center,
College of Veterinary Medicine, Kansas State University, Manhattan,
Kansas 66506,1 and Division of
Infectious Diseases, New England Medical Center, Boston,
Massachusetts 021112
Received 14 September 2000/Accepted 16 January 2001
Prevalence, antibiotic susceptibility, and genetic diversity were
determined for Escherichia coli O157:H7 isolated over 11 months from four beef cattle feedlots in southwest Kansas. From the
fecal pat (17,050) and environmental (7,134) samples collected, 57 isolates of E. coli O157:H7 were identified by use of
bacterial culture and latex agglutination (C/LA). PCR showed that 26 isolates were eaeA gene positive. Escherichia
coli O157:H7 was identified in at least one of the four
feedlots in 14 of the 16 collections by C/LA and in 9 of 16 collections
by PCR, but consecutive positive collections at a single feedlot were
rare. Overall prevalence in fecal pat samples was low (0.26% by C/LA,
and 0.08% by PCR). No detectable differences in prevalence or
antibiotic resistance were found between isolates collected from home
pens and those from hospital pens, where antibiotic use is high.
Resistant isolates were found for six of the eight antibiotics that
could be used to treat E. coli infections in food
animals, but few isolates were multidrug resistant. The high diversity
of isolates as measured by random amplification of polymorphic DNA and
other characteristics indicates that the majority of isolates were
unique and did not persist at a feedlot, but probably originated from
incoming cattle. The most surprising finding was the low frequency of
virulence markers among E. coli isolates identified
initially by C/LA as E. coli O157:H7. These results
demonstrate that better ways of screening and confirming E.
coli O157:H7 isolates are required for accurate determination
of prevalence.
0099-2240/01/$04.00+0 DOI: 10.1128/AEM.67.4.1619-1627.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Prevalence, Antibiotic Susceptibility, and Diversity of
Escherichia coli O157:H7 Isolates from a
Longitudinal Study of Beef Cattle Feedlots


*
Corresponding author. Mailing address: Food Animal
Health and Management Center, College of Veterinary Medicine, Kansas
State University, 1800 Denison Ave., Manhattan, KS 66506. Phone: (785) 532-4262. Fax: (785) 532-4288. E-mail:
galland{at}vet.ksu.edu.
This is contribution no. 01-108-J from the Kansas Agricultural
Experiment Station.
Present address: Department of Microbiology, College of Veterinary
Medicine and Biomedical Sciences, Colorado State University, Fort
Collins, CO 80523.
§
Present address: Division of Biological Sciences, Emporia State
University, Emporia, KS 66801.
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