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Infection and Immunity, January 2006, p. 758-764, Vol. 74, No. 1
0019-9567/06/$08.00+0 doi:10.1128/IAI.74.1.758-764.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
Division of Microbiology, Institute for Animal Health, High Street, Compton, Berkshire RG20 7NN, United Kingdom,1 Department of Food & Environmental Safety, Veterinary Laboratories Agency (Defra), Woodham Lane, Addlestone, Surrey KT15 3NB, United Kingdom,2 Centre for Molecular Microbiology and Infection, Division of Cell and Molecular Biology, Imperial College London, London SW7 2AZ, United Kingdom,3 Bioimaging Department, Institute for Animal Health, Ash Road, Pirbright, Surrey GU24 0NF, United Kingdom4
Received 9 August 2005/ Returned for modification 15 September 2005/ Accepted 8 October 2005
Intimin facilitates intestinal colonization by enterohemorrhagic Escherichia coli O157:H7; however, the importance of intimin binding to its translocated receptor (Tir) as opposed to cellular coreceptors is unknown. The intimin-Tir interaction is needed for optimal actin assembly under adherent bacteria in vitro, a process which requires the Tir-cytoskeleton coupling protein (TccP/EspFU) in E. coli O157:H7. Here we report that E. coli O157:H7 tir mutants are at least as attenuated as isogenic eae mutants in calves and lambs, implying that the role of intimin in the colonization of reservoir hosts can be explained largely by its binding to Tir. Mutation of tccP uncoupled actin assembly from the intimin-Tir-mediated adherence of E. coli O157:H7 in vitro but did not impair intestinal colonization in calves and lambs, implying that pedestal formation may not be necessary for persistence. However, an E. coli O157:H7 tccP mutant induced typical attaching and effacing lesions in a bovine ligated ileal loop model of infection, suggesting that TccP-independent mechanisms of actin assembly may operate in vivo.
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