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Journal of Clinical Microbiology, Oct 1995, 2616-2619, Vol 33, No. 10
MW Sanderson, JM Gay, DD Hancock, CC Gay, LK Fox and TE Besser
The sensitivities of several plating and broth enrichment methods for the
detection of Escherichia coli O157:H7 in (i) bovine fecal samples directly
inoculated with E. coli O157:H7, (ii) fecal samples from cattle in herds
previously positive for E. coli O157:H7, and (iii) fecal samples from
calves shedding E. coli O157:H7 after experimental oral inoculation were
compared. Three enrichment protocols and three plating protocols were
evaluated with directly inoculated fecal samples. All broth enrichment
methods were superior to direct plating when they were combined with
subsequent plating on sorbitol-MacConkey with cefixime and tellurite
(SMACct). SMACct was the most sensitive plating medium, and the three
alternative broth enrichment methods gave similar improvements in
sensitivity. Of 351 fecal samples from known positive herds, 24 samples
(6.8%) were positive by one or more methods. By the most sensitive plating
method, cultures of 10-g samples were slightly more sensitive (19 of 351
[5.4%]) than cotton-tipped swab fecal samples (14 of 351 [4.0%]); however,
this difference was not significant. For samples from calves orally
inoculated with E. coli O157:H7, separation by immunomagnetic beads was
slightly more sensitive (79%) than broth enrichment followed by plating at
two dilutions (10(- 3) and 10(-4)) (71%); however, this difference was not
significant. The combination of overnight enrichment of swab fecal samples
(0.1 g) and plating on SMACct at two dilutions (10(-3) and 10(-4)) appears
to be a sensitive method for detection in large-scale studies involving
hundreds of samples per week.
Copyright © 1995 by the American Society for Microbiology. All rights reserved.
Sensitivity of bacteriologic culture for detection of Escherichia coli O157:H7 in bovine feces
Department of Veterinary Clinical Sciences, Washington State University, Pullman 99164, USA.
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