Submitted to: BioMed Central (BMC) Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 18, 2013
Publication Date: December 28, 2013
Citation: Kudva, I.T., Stasko, J.A. 2013. Bison and bovine rectoanal junctions exhibit similar cellular architecture and Escherichia coli O157 adherence patterns. BioMed Central (BMC) Veterinary Research. 9(266). Available: http://www.biomedcentral.com/1746-6148/9/266. Interpretive Summary: Cattle are the primary source of Escherichia coli O157 (O157), a bacteria (micro-organism) responsible for bloody diarrhea and other serious symptoms in humans that can even lead to death. Although O157 can cause serious disease in humans, cattle infected with this bacteria remain disease free. The region of the cattle digestive tract where O157 remains (persist)for a long time is the 'rectoanal junction' (RAJ) which is close to the anus. Bison are similar to cattle in their overall structure, and the manner in which they process feed. Although bison occur in the wild, they also get same infections as cattle. There is an increased interest in bison meat since it is low in cholestrol compared to beef. This has encouraged 'farming' these animals and many times these animals are housed along side cattle and other livestock. Since O157 has been isolated from bison meat, and ground bison meat has been implicated in a multi-state O157 outbreak in the U.S., it is important to determine if bison can get infected with O157 like cattle and if this bacteria survives and adheres to the bison digestive tract in a similar manner. Any finding that supports this has important relevance to how we manage bison on farms, in the wild, and even regulate the meat derived from them. Several researchers are studying bison fecal samples from slaughter plants and farms and are finding O157 in it. We decided to go one step further and see if bison, like cattle, could have the rectoanal junction (RAJ) as the site for O157 persistence. We compared the bison and cattle RAJ tissues and found that they have similar cell structure and proteins. We also evaluated the ability of O157 to bind cells derived from bison RAJ and found that not only do O157 bind bison RAJ cells but they do so with the same adherence patterns as seen with cattle RAJ cells. Our observations support the fact that bison are likely reservoirs for O157, carrying O157 in their digestive tracts.
Technical Abstract: Escherichia coli O157 (O157) is frequently isolated from bison retail meat, a fact that is important given that bison meat has also been implicated in an O157-multistate outbreak. In addition, O157 has also been isolated from bison feces at slaughter and on farms. Cattle are well documented as O157 reservoirs, and the primary site of O157 persistence in such reservoirs is the rectoanal junction (RAJ), located at the distal end of the bovine gastrointestinal tract (GIT). Since bison and cattle share, many genetic similarities manifested as common lineage, susceptibility to infection and the nature of immune responses to infectious agents, we decided to evaluate whether the RAJ of GITs of these animals were comparable both in terms of cellular architecture and serve as sites for adherence of O157. Specifically, we compared the histo-morphologies of the RAJ, and evaluated the O157 adherence characteristics to the RAJ squamous epithelial (RSE) cells, from these two animals. We found that the RAJ of GITs of both bison and cattle RAJ demonstrated similar distribution of epithelial cell markers, villin, vimentin, cytokeratin, E-cadherin and N-cadherin. Interestingly, N-cadherin predominated in the stratified squamous epithelium probably reflecting its proliferative nature. O157 strains 86-24 SmR and EDL 933 adhered to RSE cells from both animals with similar diffuse and aggregative patterns, respectively. Our observations further support the fact that bison are likely ‘wild-life’ reservoirs for O157, harboring O157 in their GIT. Our results also extend the utility of the RSE-cell assay, previously developed (REF) to elucidate O157-cattle RAJ interactions, to studies in bison, which are warranted to determine whether these observations in vitro correlate with those occurring in vivo at the RAJ within the bison GIT.