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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Food Safety and Enteric Pathogens Research » Research » Publications at this Location » Publication #167605


item Nystrom, Evelyn

Submitted to: Veterinary Record
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/11/2004
Publication Date: 8/20/2004
Citation: Pohlenz, J.F., Nystrom, E.A. 2004. Colonisation of Escherichia coli O157:H7 on squamous epithelial cells at the rectal anal junction. Veterinary Record. 155(8):248.

Interpretive Summary:

Technical Abstract: Escherichia coli O157:H7 and other Shiga toxin-producing E. coli (STEC) serovars cause hemorrhagic colitis in man. This serious disease may result in a systemic hemolytic uremic syndrome (HUS) associated with kidney damage and lifelong disturbances of the central nervous system. Cattle are the main source of O157:H7 strains associated with human disease. STEC bacteria are found in the intestinal tract of healthy cattle and are spread into the environment by fecal shedding. To avoid human contamination, it is important to exclude these organisms from cattle. To do this one needs to know the sites where these bacteria attach in the digestive tract of cattle. The rectal anal junction appears to be a prominent site. We have pursued this issue and observed attached O157:H7 bacteria on the stratified columnar epithelium at the rectal anal junction, as well as on enterocytes, in eight out of eight orally inoculated 3- to 4-month-old calves. Four of the calves were pretreated with dexamethasone, and four were not pretreated. Bacteria tightly attached to the squamous epithelial cells were seen in tissue samples stained with H&E and in samples immunohistochemically stained to identify O157:H7 bacteria. Sections with adherent bacteria were detached from both types of samples and reinvestigated by transmission electron microscopy. The O157:H7 bacteria were tightly attached to squamous epithelial cells of the rectal anal junction. The squamous epithelial cells were separated from each other and in the process of sloughing. At sites of bacterial attachment, the cells expressed typical pedestals, similar to those produced by colonic enterocytes colonized by O157:H7. Eosinophils were seen penetrating into the intercellular spaces at sites of attachment in H&E stained samples. To our knowledge, O157:H7 attachment to squamous epithelial cells at this site has not been described. Our findings confirm that the rectal anal junction is a prominent site of O157:H7 colonization in cattle and extend previous studies by showing that O157:H7 colonization of squamous epithelial cells results in a lesion that is similar to the attachment and effacement (A/E) lesion characteristic of that produced by O157:H7 on enterocytes. However, there is no effacement, as this phenomenon is unique to cells with microvilli, which are the effaced organelles.