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United States Department of Agriculture

Agricultural Research Service

Title: Model for Competitive Colonization of Sheep by E. Coli O157:h7

Authors
item Cornick, N - IOWA STATE UNIVERSITY
item Casey, Thomas
item Moon, H - IOWA STATE UNIVERSITY

Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: June 3, 1999
Publication Date: N/A

Technical Abstract: E. coli O157:H7 and other serogroups of Shiga toxin-producing E. coli (STEC) cause gastrointestinal disease in humans. Ruminants are apparently more frequently colonized by STEC than other animals. We hypothesized that STEC are uniquely adapted to persist in the ruminant intestinal tract, compared to other pathotypes of E. coli. To test this hypothesis we developed a cocktail of E. coli strains containing STEC serogroup O157:H7 (2), enterotoxigenic E. coli (ETEC, 2), and enteropathogenic E. coli (EPEC, 1). The strains were chosen so they could be distinguished from each other and from background flora. Eighteen sheep were inoculated with all 5 strains (at 10**7 or 10**10 CFU/strain) and colonization was monitored by fecal culture. All strains were recovered from the sheep by 2 days postinoculation (pi). At 2 weeks pi STEC strains 86-24 and 3081 were detected from 16/18 and 11/18 sheep, respectively. ETEC strains 2041 and 637 were isolated from 9/18 and 1/18 sheep, and the EPEC strain was detected in 3/18 sheep. The magnitude of colonization at 2 weeks pi ranged from 0-10**4 CFU/g per strain. At 2 months pi STEC strains 86-24 and 3081 were detected from 4/18 and 6/18 sheep. ETEC strain 2041 was detected from 3/18 sheep and ETEC strain 637 and the EPEC strain were not recovered. The range of colonization at 2 months pi varied from 0-10**2 CFU/g. ETEC strain 2041 colonized and persisted with similar incidence as the 2 STEC strains when it was given at the 10**10 CFU dose but not at the 10**7 CFU dose. These results are consistent with a hypothesis that STEC persist in the ruminant intestinal tract longer than do other pathotypes of E. coli.

Last Modified: 4/19/2014
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