Enterohaemorrhagic Escherichia coli O157 : H7 target Peyer's patches in humans and cause attaching/effacing lesions in both human and bovine intestine

Background-Enterohaemorrhagic Escherichia coli (EHEC) constitute a signific ant risk to human health worldwide, and infections, particularly with serog roup O157:H7, are associated with consumption of a variety of food and wate r vehicles, particularly food of bovine origin. EHEC cause acute gastroente ritis, bloody diarrhoea, and haemorrhagic colitis; up to 10% of cases devel op severe complications, including the haemolytic uraemic syndrome, with a 5% case fatality. A virulence characteristic of enteropathogenic E coli, th e attaching/effacing lesion, is considered to be important in EHEC. However , although EHEC produce this lesion on cultured human cells, this has not b een demonstrated on human intestinal mucosal surfaces. In addition, the ini tial site(s) of colonisation of EHEC in humans is not known. Aims-To assess the association of EHEC O157:H7 with paediatric and bovine i ntestine using in vitro organ culture and determine if attaching/effacing l esions occur. Methods-Ultrastructural analysis of in vitro intestinal organ cultures of h uman small and large intestine was used to investigate adhesion of O157:H7 EHEC to intestinal surfaces. Bovine intestinal organ culture was used to ex amine the pathology produced by the same EHEC strain in cattle. Results-The study showed that EHEC O157:H7 adhered to human intestinal muco sa. Binding and attaching/effacing lesion formation of O157:H7 in humans wa s restricted to follicle associated epithelium of Peyer's patches. The same strain caused attaching/effacing lesions on bovine mucosa. Conclusions-O157:H7 targets follicle associated epithelium in humans where it causes attaching/effacing lesions. The same human isolate can cause atta ching/effacing lesions in cattle, indicating that similar pathogenic mechan isms operate across human and bovine species.