Submitted to: Virulence Mechanisms of Bacterial Pathogens
Publication Type: Abstract Only
Publication Acceptance Date: 9/6/2006
Publication Date: 9/6/2006
Citation: Nystrom, E.A., Pohlenz, J.F., Stoffregen, W.C. 2006. Squamous epithelial cells are early attachment sites for shigatoxigenic Escherichia coli O157:H7 in cattle [abstract]. Virulence Mechanisms of Bacterial Pathogens. p. 33.
Technical Abstract: Shigatoxigenic Escherichia coli (STEC) are commonly found in the gastrointestinal tracts of healthy cattle and spread into the environment by fecal shedding. The terminal rectal mucosa is a prominent colonization site for the human pathogen STEC O157:H7 in cattle. We have necropsied and examined 55 weaned calves (3-4-mos) 4d after inoculation with 1010 CFU of STEC O157:H7 to identify early colonization sites. Sites most likely to contain O157+ bacteria were the rectal anal junction (RAJ), distal colon, and ileal-cecal valve, where bacteria were attached to enterocytes and associated with characteristic attaching and effacing lesions. Surprisingly, O157+ bacteria also attached to squamous epithelial cells in the RAJ. The discovery that O157:H7 bound early to enterocytes and squamous epithelial cells in the RAJ extends the evidence that this is an important colonization site and identifies squamous epithelial cells as STEC colonization targets. Recently, a rectal anal mucosal swab (RAMS) culture technique was shown to be more sensitive than fecal culture for identifying O157:H7-colonized cattle. We found that bovine RAMS samples can also be used for analyzing O157:H7 adherence to squamous epithelial cells. Examination by IFA showed squamous epithelial cells with adherent O157+ bacteria in RAMS samples obtained from O157:H7-inoculated calves at 1 to 4d PI. O157:H7 bacteria also adhered in vitro to squamous epithelial cells in RAMS from non-infected calves. The possibility of using easily obtained RAMS samples for STEC adherence studies, as well as for bacterial cultures, will facilitate the identification of O157:H7 colonized cattle and elucidation of O157:H7 colonization mechanisms. Dedicated to the memory of Joachim Pohlenz, June 5, 1936 to January 10, 2006