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United States Department of Agriculture

Agricultural Research Service

Title: Persistent Colonization of Sheep by Escherichia Coli O157:h7 and Other E. Coli Pathotypes

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

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 15, 2000
Publication Date: N/A

Interpretive Summary: Escherichia coli O157:H7 bacteria cause serious foodborne illness in about 75,000 people each year, including about 2,000 cases that require hospitalization and 50 deaths. People become ill by eating undercooked meat or other food that is contaminated with E. coli O157:H7 bacteria. These bacteria seem to be in the intestines and feces of normal, healthy ruminants, such as cattle and sheep, more often than other animals. We wanted to know if E. coli O157:H7 have special characteristics, not present in other E. coli, that allow these bacteria to survive and grow in cattle and sheep. We found that E. coli O157:H7 stayed in the intestines and in feces from sheep longer than several other kinds of E. coli. This suggests that E. coli O157:H7 have special, unknown characteristics that allow these bacteria to survive and grow in sheep intestines and feces. Our finding are an important first step for identifying these characteristics and for developing ways to reduce the amount of E. coli O157:H7 in the intestines and feces from cattle and sheep. This information is useful for other scientists and can be used to develop ways to reduce or prevent E. coli O157:H7 infection in cattle and sheep and to prevent human illness and death caused by these bacteria.

Technical Abstract: Shiga toxin-producing E. coli (STEC) are an important cause of foodborne illness in humans. Ruminants appear to be more frequently colonized by STEC than are other animals, but the reason(s) for this are unknown. We compared the frequency, magnitude, duration, and transmissibility of colonization in sheep by E. coli O157:H7 to that of other pathotypes of E. coli. Young adult sheep were simultaneously inoculated with a cocktail consisting of 2 strains of O157:H7, 2 strains of enterotoxigenic E. coli (ETEC), and 1 strain of enteropathogenic E. coli. Both STEC strains and ETEC strain 2041 were given at either 10**7 or 10**10 CFU/strain/animal. The other strains were given only at 10**10 CFU/strain. We found no consistent differences among pathotypes in the frequency, magnitude, and transmissibility of colonization. However, the STEC strains tended to persist to 2 weeks and 2 months post-inoculation more frequently than did the other pathotypes. The tendency for persistence of the STEC strains was apparent following an inoculation dose of either 10**7 or 10**10 CFU. One of the ETEC strains also persisted when inoculated at 10**10 CFU. However, in contrast to the STEC strains, it did not persist when inoculated at 10**7 CFU. These results support the hypothesis that STEC are better adapted to persist in the alimentary tract of sheep than are other pathotypes of E. coli.

Last Modified: 8/22/2014
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