Abstract
BackgroundEscherichia coli O157 (E. coli O157) has been isolated from bison retail meat, a fact that is important given that bison meat has been implicated in an E. coli O157-multistate outbreak. In addition, E. coli O157 has also been isolated from bison feces at slaughter and on farms. Cattle are well documented as E. coli O157 reservoirs, and the primary site of E. coli O157 persistence in such reservoirs is the rectoanal junction (RAJ), located at the distal end of the bovine gastrointestinal tract. 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 these animals were comparable both in terms of cellular architecture and as sites for adherence of E. coli O157. Specifically, we compared the histo-morphologies of the RAJ and evaluated the E. coli O157 adherence characteristics to the RAJ squamous epithelial (RSE) cells, from these two species.ResultsWe found that the RAJ of both bison and cattle demonstrated similar distribution of epithelial cell markers villin, vimentin, cytokeratin, E-cadherin and N-cadherin. Interestingly, N-cadherin predominated in the stratified squamous epithelium reflecting its proliferative nature. E. coli O157 strains 86–24 SmR and EDL 933 adhered to RSE cells from both animals with similar diffuse and aggregative patterns, respectively.ConclusionOur observations further support the fact that bison are likely ‘wildlife’ reservoirs for E. coli O157, harboring these bacteria in their gastrointestinal tract. Our results also extend the utility of the RSE-cell assay, previously developed to elucidate E. coli 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 gastrointestinal tract.
Highlights
Escherichia coli O157 (E. coli O157) has been isolated from bison retail meat, a fact that is important given that bison meat has been implicated in an E. coli O157-multistate outbreak
The rectoanal junction (RAJ) sections from both cattle exposed to E. coli O157 and those that were never exposed to E. coli O157 demonstrated the same histo-morphology as previously described [30,33,43] and observed by analyzing tissue sections by light, fluorescence and transmission electron microscopy
Regardless of their age and breed, the RAJ was characterized by an abrupt replacement of columnar epithelial cells by stratified squamous epithelial cells (Figure 1)
Summary
Escherichia coli O157 (E. coli O157) has been isolated from bison retail meat, a fact that is important given that bison meat has been implicated in an E. coli O157-multistate outbreak. 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 these animals were comparable both in terms of cellular architecture and as sites for adherence of E. coli O157. A renewed interest in the low cholesterol and high protein bison meat has resulted in these animals being actively farmed, thereby enabling transmission of disease agents among bison and other livestock [7,11]. Studies evaluating the fecal E. coli serotypes indicate that while E. coli O157:H7 (E. coli O157) may not be consistently isolated from the gastrointestinal tracts of wild bison, it is prevalent in 17-83% of farmed bison much like its recovery from farmed Asian water buffaloes [12,13,14]
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