title: Gastrointestinal tract location of Escherichia coli O157:H7 in ruminants.
abstract: Experimentally inoculated sheep and cattle were used as models of natural ruminant infection to investigate the pattern of Escherichia coli O157:H7 shedding and gastrointestinal tract (GIT) location. Eighteen forage-fed cattle were orally inoculated with E. coli O157:H7, and fecal samples were cultured for the bacteria. Three distinct patterns of shedding were observed: 1 month, 1 week, and 2 months or more. Similar patterns were confirmed among 29 forage-fed sheep and four cannulated steers. To identify the GIT location of E. coli O157:H7, sheep were sacrificed at weekly intervals postinoculation and tissue and digesta cultures were taken from the rumen, abomasum, duodenum, lower ileum, cecum, ascending colon, descending colon, and rectum. E. coli O157:H7 was most prevalent in the lower GIT digesta, specifically the cecum, colon, and feces. The bacteria were only inconsistently cultured from tissue samples and only during the first week postinoculation. These results were supported in studies of four Angus steers with cannulae inserted into both the rumen and duodenum. After the steers were inoculated, ruminal, duodenal, and fecal samples were cultured periodically over the course of the infection. The predominant location of E. coli O157:H7 persistence was the lower GIT. E. coli O157:H7 was rarely cultured from the rumen or duodenum after the first week postinoculation, and this did not predict if animals went on to shed the bacteria for 1 week or 1 month. These findings suggest the colon as the site for E. coli O157:H7 persistence and proliferation in mature ruminant animals.
authors.affiliation: Department of Microbiology, Molecular Biology and Biochemistry, University of Idaho, Moscow, Idaho 83844, USA.
authors.forename: Luke J
authors.initials: LJ
authors.lastname: Grauke
authors.forename: Indira T
authors.initials: IT
authors.lastname: Kudva
authors.forename: Jang Won
authors.initials: JW
authors.lastname: Yoon
authors.forename: Carl W
authors.initials: CW
authors.lastname: Hunt
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Williams
authors.forename: Carolyn J
authors.initials: CJ
authors.lastname: Hovde
mesh_terms: D000818:Animals; D002417:Cattle; D004064:Digestive System / Q000382:microbiology*; D004195:Disease Models, Animal; D004926:Escherichia coli / Q000502:physiology*; D004927:Escherichia coli Infections / Q000382:microbiology*; D012756:Sheep