Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 22, 2012
Publication Date: May 20, 2012
Citation: Kudva, I.T., Stasko, J.A. 2012. Escherichia coli O157 adherence to the bovine recto-anal junction (RAJ) squamous epithelial cells is mediated by adhesins other than those encoded by genes on the Locus of Enterocyte Attachment (LEE) pathogenicity island [abstract]. American Society for Microbiology General Meeting, June 16-19, 2012, San Francisco, California. p. 215. Technical Abstract: Escherichia coli O157 (O157) persist in the gastrointestinal tracts (GIT) of bovine reservoirs primarily by adhering to the mucocutaneous, recto-anal junction (RAJ), comprising of both follicle-associated-epithelial (FAE) cells proximally and stratified squamous epithelial (RSE) cells distally. Whereas the locus of enterocyte effacement (LEE) encoded proteins, including intimin-gamma, have been demonstrated to play a central role in the adherence of this human pathogen to the FAE via the formation of microcolonies, proteins contributing to diffuse adherence to the RSE cells remain unelucidated. To specifically address this, we (i) studied O157 adherence to RSE cells in vitro; (ii) evaluated the role of LEE-proteins in O157-RSE cell interactions using polyclonal antisera against individual LEE-proteins in adherence-inhibition assays; (iii) validated observations made using isogenic intimin-gamma deletion derivative of O157; and (iv) commenced studies to identify novel proteins contributing to O157 adherence to RSE cells. O157 strains were interacted with RSE cells in vitro, using the adherence assay protocol standardized in our laboratory. Immunofluorescence and transmission electron microscopy studies confirmed that this O157 adherence to RSE cells was not transient. Polyclonal antisera against recombinant intimin-gamma, EspA, EspB and Tir proteins were evaluated at various dilutions for their ability to block O157 adherence to RSE cells, as has been shown with HEp-2 cells. Interestingly, none of the antisera tested could prevent O157 adherence to RSE cells strongly suggesting that intimin-gamma and other LEE proteins did not have a role in this adherence. This observation was further supported by the continued adherence of an isogenic intimin-gamma deletion derivative of O157 to RSE cells with the same pattern as the wild-type O157. Results of this study indicate that O157 persistence at the RAJ is complex, with disparate mechanisms operating in the adherence of this pathogen to the two histologically distinct cell types comprising this site. Intimin and the LEE-encoded proteins do not seem to play a role in O157 adherence to RSE cells. Ongoing studies to identify novel proteins that play a role in O157 adherence to RSE cells will allow for development of efficacious modalities to eliminate O157 from the bovine GIT.