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Infection and Immunity, August 2006, p. 4685-4693, Vol. 74, No. 8
0019-9567/06/$08.00+0     doi:10.1128/IAI.00406-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Role of Escherichia coli O157:H7 Virulence Factors in Colonization at the Bovine Terminal Rectal Mucosa

Haiqing Sheng, Ji Youn Lim, Hannah J. Knecht, Jie Li, and Carolyn J. Hovde*

University of Idaho, Department of Microbiology, Molecular Biology, and Biochemistry, Moscow, Idaho 83844-3052

Received 13 March 2006/ Returned for modification 17 April 2006/ Accepted 17 May 2006

The human pathogen Escherichia coli O157:H7 causes hemorrhagic colitis and life-threatening sequelae and transiently colonizes healthy cattle at the terminal rectal mucosa. This study analyzed virulence factors important for the clinical manifestations of human E. coli O157:H7 infection for their contribution to the persistence of E. coli in cattle. The colonizing ability of E. coli O157:H7 was compared with those of nonpathogenic E. coli K-12 and isogenic deletion mutants missing Shiga toxin (Stx), the adhesin intimin, its receptor Tir, hemolysin, or the ~92-kb pO157. Fully ruminant steers received a single rectal application of one E. coli strain so that effects of mucosal attachment and survival at the terminal rectum could be measured without the impact of bacterial passage through the entire gastrointestinal tract. Colonization was monitored by sensitive recto-anal junction mucosal swab culture. Nonpathogenic E. coli K-12 did not colonize as well as E. coli O157:H7 at the bovine terminal rectal mucosa. The E. coli O157:H7 best able to persist had intimin, Tir, and the pO157. Strains missing even one of these factors were recovered in lower numbers and were cleared faster than the wild type. In contrast, E. coli O157:H7 strains that were missing Stx or hemolysin colonized like the wild type. For these three strains, the number of bacteria increased between days 1 and 4 postapplication and then decreased slowly. In contrast, the numbers of noncolonizing strains (K-12, {Delta}tir, and {Delta}eae) decreased from the day of application. These patterns consistently predicted long-term colonization or clearance of the bacteria from the bovine terminal rectal mucosa.

* Corresponding author. Mailing address: Department of Microbiology, Molecular Biology, and Biochemistry, University of Idaho, Moscow, ID 83844-3052. Phone: (208) 885-5906. Fax: (208) 885-6518. E-mail: cbohach{at}uidaho.edu.

Editor: J. T. Barbieri

Infection and Immunity, August 2006, p. 4685-4693, Vol. 74, No. 8
0019-9567/06/$08.00+0     doi:10.1128/IAI.00406-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



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