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Infect. Immun. doi:10.1128/IAI.00778-07
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Lactobacillus rhamnosus strain GG prevents enterohemorrhagic Escherichia coli O157:H7-induced changes in epithelial barrier function

Research Institute, Hospital for Sick Children, and Departments of Paediatrics and Laboratory Medicine & Pathobiology, University of Toronto, Toronto, Ontario, CANADA

^* To whom correspondence should be addressed. Email: philip.sherman{at}sickkids.ca.

	Abstract

Enterohemorrhagic Escherichia coli O157:H7 (EHEC) intimately attaches to intestinal epithelial monolayers and produces attaching-effacing (A-E) lesions. In addition, EHEC infection causes disruptions of intercellular tight junctions, leading to clinical sequelae of acute diarrhea, hemorrhagic colitis and the hemolytic uremic syndrome. Current therapy remains supportive since antibiotic therapy increases the risk of systemic complications. This study focuses on the potential therapeutic effect of an alternative form of therapy, probiotic Lactobacillus rhamnosus strain GG, to attenuate EHEC-induced changes of paracellular permeability in polarized MDCK-I and T84 epithelial monolayers. Changes in epithelial morphology, electrical resistance, dextran permeability, and distribution/expression of claudin-1 and ZO-1 were assessed using phase-contrast, immunofluoresence, transmission electron microscopy and macromolecular flux. This study demonstrates that pre-treatment of polarized MDCK-I and T84 cells with probiotic L. rhamnosus GG reduces morphological changes and diminishes the number of A-E lesions induced in response to EHEC O157:H7 infection. With probiotic pre-treatment there was a corresponding attenuation of the EHEC-induced drop in electrical resistance and increase in barrier permeability assays. In addition, L. rhamnosus GG protected epithelial monolayers against EHEC-induced redistribution of claudin-1 and ZO-1 tight junction proteins. In contrast to the effects seen with the live probiotic, heat- inactivated L. rhamnosus GG had no effect on EHEC binding and A-E lesion formation or disruption of barrier function. Collectively, these findings provide in vitro evidence that the probiotic Lactobacillus rhamnosus strain GG could prove effective as management to prevent injury of the epithelial cell barrier induced by attaching-effacing bacterial enteropathogens.