title: Heterogeneity in enterohemorrhagic Escherichia coli O157:H7 fecal shedding in cattle is related to Escherichia coli O157:H7 colonization of the small and large intestine.
abstract: In the last decade, Escherichia coli O157:H7 have emerged as important pathogens of the gastrointestinal tract of humans. Healthy cattle have been identified as the primary reservoir, however, the factors affecting heterogeneous E. coli O157:H7 fecal shedding are not fully understood. The aim of this study was to investigate the contribution of E. coli O157:H7 colonization of small and large intestinal sites to the heterogeneity of fecal shedding in cattle. There was a dose-dependant E. coli O157:H7 E318N colonization of duodenum, jejunum, ileum, cecum, ascending colon, spiral colon, descending colon, and the rectoanal junction in vitro with no difference in E. coli O157:H7 colonization of the rectoanal junction and other intestinal sites. There were 10-100 times greater E. coli O157:H7 colonization of intestinal sites from persistent shedding cattle compared with non persistent shedding cattle. Novel pathologies were associated with E. coli O157:H7 colonization sites in the small and large intestine. The first pathology, focal petechiae, was present throughout the intestinal tract of cattle that ceased shedding E. coli O157:H7 for 5-12 weeks or in the jejunum, ileum, cecum, and ascending colon of cattle shedding E. coli O157:H7 for 4-5 months. The second pathology, mucosal hemorrhages, was present in the same sites as the focal petechiae in cattle shedding for 5 months and these hemorrhages were in the final stages of repair. Several features of these hemorrhages support this conclusion including the brown appearance, low amount of classic E. coli O157:H7 induced A/E lesions, flattened epithelium, and blunted villi. Although mucosal hemorrhages were present in the jejunum, ileum, cecum, and ascending colon in cattle shedding for 4 months, many other pathologies were also present that were indicative of hemorrhagic enteritis as evidenced by the blood red appearance of hemorrhages, severe edema, and dark red erythema. Escherichia coli O157:H7 were associated with both pathologies suggesting it is the causative agent. The current study supports a relationship between the amount of E. coli O157:H7 colonization in intestinal sites and heterogeneous fecal shedding by cattle.
authors.affiliation: Lethbridge Research Centre, Agriculture and Agri-Food Canada, Lethbridge, ABT1J4B1, Canada. bainesd@agr.gc.ca
authors.forename: Danica
authors.initials: D
authors.lastname: Baines
authors.forename: Byron
authors.initials: B
authors.lastname: Lee
authors.forename: Tim
authors.initials: T
authors.lastname: McAllister
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology* / Q000503:physiopathology; D002432:Cecum / Q000382:microbiology; D044682:Colon, Ascending / Q000166:cytology / Q000382:microbiology; D044683:Colon, Descending / Q000382:microbiology; D004386:Duodenum / Q000382:microbiology; D004751:Enteritis / Q000382:microbiology / Q000662:veterinary*; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000472:pathogenicity*; D005243:Feces; D006471:Gastrointestinal Hemorrhage / Q000382:microbiology / Q000662:veterinary*; D006801:Humans; D007082:Ileum / Q000382:microbiology; D007583:Jejunum / Q000382:microbiology; D008297:Male; D011693:Purpura / Q000382:microbiology; D012007:Rectum / Q000382:microbiology; D013997:Time Factors