Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 12/4/2005
Publication Date: 12/4/2005
Citation: Nystrom, E.A., Pohlenz, J.F., Stoffregen, W.C., Moon, H.W. STEC O157:H7 attachment sites in the bovine digestive tract [abstract]. Conference of Research Workers in Animal Diseases. p. 126.
Technical Abstract: Cattle are the main source of Shiga toxin-producing Escherichia coli (STEC) O157:H7 strains associated with human disease. STEC are found in the gastro-intestinal tracts of healthy cattle and are spread into the environment by fecal shedding. The rectal anal junction is a prominent O157:H7 colonization site during the carrier-shedder state in cattle. We are using bovine infection models to identify sites where O157:H7 bacteria initially colonize cattle. Weaned 3- to -4-month-old calves (some treated with dexamethasone) were fasted 48 h prior to oral or intra-rumenal inoculation with 10**10 CFU of O157:H7, necropsied 4 d pi, and examined microbiologically and histologically, including specific immuno-peroxidase staining for O157. All calves remained healthy throughout the study. O157:H7 bacteria were recovered in higher numbers and attached O157**+ bacteria were more common in dexamethasone-treated calves than in non-treated calves. The rectal anal junction, distal colon, and ileal-cecal valve were sites most likely to contain O157:H7 bacteria, in comparison to at least 5 other regularly-sampled sites. In some dexamethasone-treated calves, O157:H7 bacteria were also found in the ileum and gall bladder. O157**+ bacteria were attached to enterocytes in the rectal anal junction, distal colon, cecum, ileal-cecal valve, and ileum, and to epithelial cells in the gall bladder. Bacterial attachment to enterocytes and gall bladder epithelial cells was associated with characteristic attachment and effacement lesions. Surprisingly, O157**+ bacteria were also attached to squamous epithelial cells in the rectal anal junction, and the squamous epithelial cells expressed pedestals, similar to those produced by enterocytes colonized by STEC O157:H7, at sites where bacteria were attached. Our discovery of O157**+ bacteria attached to squamous epithelial cells in the rectal anal junction extends the evidence that this is a prominent site of STEC O157:H7 colonization in cattle. However, our data clearly demonstrate that other sites in the bovine digestive tract are also potential niches for O157:H7.