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Infection and Immunity, November 2005, p. 7657-7668, Vol. 73, No. 11
0019-9567/05/$08.00+0     doi:10.1128/IAI.73.11.7657-7668.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Uropathogenic Escherichia coli Flagella Aid in Efficient Urinary Tract Colonization

Kelly J. Wright,1,{dagger} Patrick C. Seed,1,2,{dagger} and Scott J. Hultgren1*

Department of Molecular Microbiology, Box 8230,1 Division of Pediatric Infectious Diseases, Box 8116, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, Missouri 631102

Received 16 May 2005/ Returned for modification 30 June 2005/ Accepted 26 July 2005

In the murine model of urinary tract infections (UTI), cystitis by uropathogenic Escherichia coli (UPEC) occurs through an intimate relationship with the bladder superficial umbrella cell entailing cycles of adherence, invasion, intracellular bacterial community (IBC) formation, and dispersal (fluxing) from the intracellular environment. IBC dispersal is a key step that results in the spread of bacteria over the epithelial surface to initiate additional rounds of IBC formation. We investigated the role of flagella in mediating adherence and motility during UTI, hypothesizing that the dispersion of the IBC would be incomplete in the absence of motility, thus interrupting the IBC pathway and attenuating the infection. Using gfp reporter fusions, the expression of the flagellar class I flhDC and class III fliC genes was monitored to track key points of regulation throughout the pathogenic cascade. In vitro, growth under conditions promoting motility resulted in the robust expression of both fusions. In contrast, only the class I fusion produced significant expression throughout early stages of IBC development including the dispersion stage. Thus, unlike in vitro modeling of motility, the regulatory cascade appeared incomplete in vivo. Throughout IBC formation, nonmotile {Delta}fliC mutants achieved the same number of IBCs as the wild-type (wt) strain, demonstrating that flagella are neither essential nor required for first- or second-generation IBC formation. However, in competition experiments between wt and {Delta}fliC strains, the wt was shown to have a fitness advantage in persisting throughout the urinary tract for 2 weeks, demonstrating a subtle but measurable role for flagella in virulence.


* Corresponding author. Mailing address: Department of Molecular Microbiology, Box 8230, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110. Phone: (314) 362-6772. Fax: (314) 362-1998. E-mail: hultgren{at}borcim.wustl.edu.

Editor: D. L. Burns

{dagger} K.J.W. and P.C.S. contributed equally to this work.


Infection and Immunity, November 2005, p. 7657-7668, Vol. 73, No. 11
0019-9567/05/$08.00+0     doi:10.1128/IAI.73.11.7657-7668.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.




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