Food Safety and Enteric Pathogens Research Unit, National Animal Disease Center, Agricultural Research Service, U,S, Department of Agriculture, Ames, IA 50010, USA.
BMC Vet Res. 2013 Dec 28;9:266. doi: 10.1186/1746-6148-9-266.
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. 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.
We 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.
Our 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.
大肠杆菌 O157（E. coli O157）已从野牛零售肉中分离出来，这一事实很重要，因为野牛肉已被牵连到大肠杆菌 O157 的多州爆发中。此外，大肠杆菌 O157 也已从屠宰场和农场的野牛粪便中分离出来。牛被充分记录为大肠杆菌 O157 的储主，而这种储主中大肠杆菌 O157 的持续存在的主要部位是直肠肛门交界处（RAJ），位于牛的胃肠道的远端。由于野牛和牛具有许多表现为共同谱系的遗传相似性，对感染的易感性以及对感染性剂的免疫反应的性质，我们决定评估这些动物的 RAJ 在细胞结构和大肠杆菌 O157 黏附部位方面是否相似。具体而言，我们比较了 RAJ 的组织形态，并评估了这两种物种的 RAJ 鳞状上皮（RSE）细胞对大肠杆菌 O157 的黏附特性。
我们发现，野牛和牛的 RAJ 均表现出上皮细胞标志物 villin、vimentin、细胞角蛋白、E-钙粘蛋白和 N-钙粘蛋白的相似分布。有趣的是，N-钙粘蛋白在分层鳞状上皮中占主导地位，反映了其增殖性质。大肠杆菌 O157 菌株 86-24 SmR 和 EDL 933 分别以类似的弥散和聚集模式黏附于来自这两种动物的 RSE 细胞。
我们的观察结果进一步支持了野牛可能是大肠杆菌 O157 的“野生动物”储主的事实，其胃肠道中存在这些细菌。我们的结果还扩展了 RSE 细胞测定法的用途，该测定法先前被开发用于阐明大肠杆菌 O157-牛 RAJ 相互作用，以用于野牛研究，这是必要的，以确定这些在体外的观察结果是否与野牛胃肠道内 RAJ 中发生的那些观察结果相关。
