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Applied and Environmental Microbiology, February 2007, p. 671-679, Vol. 73, No. 3
0099-2240/07/$08.00+0 doi:10.1128/AEM.01035-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.
Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, P.O. Box 647040,1 School of Molecular Biosciences, P.O. Box 644234, Washington State University, Pullman, Washington 99164,3 Division of Gastroenterology and Nutrition, Edward Mallinckrodt Department of Pediatrics, Washington University School of Medicine, Campus Box 8208, 660 South Euclid Avenue, St. Louis, Missouri 63110,2 Microbial Evolution Laboratory, National Food Safety and Toxicology Center, Michigan State University, East Lansing, Michigan 48824,4 Animal Health Research Unit, U.S. Meat Animal Research Center, ARS, USDA, P.O. Box 166, State Spur 18D, Clay Center, Nebraska 689335
Received 4 May 2006/ Accepted 18 November 2006
Escherichia coli O157:H7, a zoonotic human pathogen for which domestic cattle are a reservoir host, produces a Shiga toxin(s) (Stx) encoded by bacteriophages. Chromosomal insertion sites of these bacteriophages define three principal genotypes (clusters 1 to 3) among clinical isolates of E. coli O157:H7. Stx-encoding bacteriophage insertion site genotypes of 282 clinical and 80 bovine isolates were evaluated. A total of 268 (95.0%) of the clinical isolates, but only 41 (51.3%) of the bovine isolates, belonged to cluster 1, 2, or 3 (P < 0.001). Thirteen additional genotypes were identified in isolates from both cattle and humans (four genotypes), from only cattle (seven genotypes), or from only humans (two genotypes). Two other markers previously associated with isolates from cattle or with clinical isolates showed similar associations with genotype groups within bovine isolates; the tir allele sp-1 and the Q933W allele were under- and overrepresented, respectively, among cluster 1 to 3 genotypes. Stx-encoding bacteriophage insertion site typing demonstrated that there is broad genetic diversity of E. coli O157:H7 in the bovine reservoir and that numerous genotypes are significantly underrepresented among clinical isolates, consistent with the possibility that there is reduced virulence or transmissibility to humans of some bovine E. coli O157:H7 genotypes.
Published ahead of print on 1 December 2006.
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