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Infection and Immunity, June 2003, p. 3088-3096, Vol. 71, No. 6
0019-9567/03/$08.00+0     DOI: 10.1128/IAI.71.6.3088-3096.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

degS Is Necessary for Virulence and Is among Extraintestinal Escherichia coli Genes Induced in Murine Peritonitis

Peter Redford, Paula L. Roesch, and Rodney A. Welch*

Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin 53706-1532

Received 20 November 2002/ Returned for modification 8 January 2003/ Accepted 24 February 2003

Extraintestinal Escherichia coli strains cause meningitis, sepsis, urinary tract infection, and other infections outside the bowel. We examined here extraintestinal E. coli strain CFT073 by differential fluorescence induction. Pools of CFT073 clones carrying a CFT073 genomic fragment library in a promoterless gfp vector were inoculated intraperitoneally into mice; bacteria were recovered by lavage 6 h later and then subjected to fluorescence-activated cell sorting. Eleven promoters were found to be active in the mouse but not in Luria-Bertani (LB) broth culture. Three are linked to genes for enterobactin, aerobactin, and yersiniabactin. Three others are linked to the metabolic genes metA, gltB, and sucA, and another was linked to iha, a possible adhesin. Three lie before open reading frames of unknown function. One promoter is associated with degS, an inner membrane protease. Mutants of the in vivo-induced loci were tested in competition with the wild type in mouse peritonitis. Of the mutants tested, only CFT073 degS was found to be attenuated in peritoneal and in urinary tract infection, with virulence restored by complementation. CFT073 degS shows growth similar to that of the wild type at 37°C but is impaired at 43°C or in 3% ethanol LB broth at 37°C. Compared to the wild type, the mutant shows similar serum survival, motility, hemolysis, erythrocyte agglutination, and tolerance to oxidative stress. It also has the same lipopolysaccharide appearance on a silver-stained gel. The basis for the virulence attenuation is unclear, but because DegS is needed for {sigma}E activity, our findings implicate {sigma}E and its regulon in E. coli extraintestinal pathogenesis.


* Corresponding author. Mailing address: Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Rm. 481 MSB, 1300 University Ave., Madison, WI 53706-1532. Phone: (608) 263-2700. Fax: (608) 262-8418. E-mail: rawelch{at}facstaff.wisc.edu.

Editor: A. D. O'Brien


Infection and Immunity, June 2003, p. 3088-3096, Vol. 71, No. 6
0019-9567/03/$08.00+0     DOI: 10.1128/IAI.71.6.3088-3096.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.




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