Thesis
International comparison of shiga toxin-encoding bacteriophage insertion site genotypes of clinical, bovine and environmental E. coli O157 isolates
Washington State University
Master of Science (MS), Washington State University
2008
Handle:
https://hdl.handle.net/2376/103224
Abstract
Enterohemorrhagic Escherichia coli O157:H7 (EHEC O157) is a major cause of bloody diarrhea and hemolytic uremic syndrome (HUS) worldwide, although the annual incidence of EHEC O157 associated HUS varies from 0.01 to 0.41 cases per 100,000 population in different countries. Cattle are considered the principal reservoir of EHEC O157 and some genotypes of EHEC O157 commonly isolated from US cattle are rarely associated with human disease. We compared the genotype distribution of EHEC O157 in the cattle reservoir with human EHEC O157 disease incidence internationally to test the hypothesis that EHEC O157 disease incidence is due to differential exposure to genotypes of differing virulence. In this study, genotypes were defined by Shiga toxin-encoding bacteriophage insertion sites (Stx insertion genotypes). The relative frequencies of Stx insertion genotypes in isolates from the bovine reservoir were unrelated to HUS incidence, internationally (P>0.05). The distribution of Stx insertion genotypes of clinical isolates from Australia differed from those of the US (P<0.017), while clinical isolates from Japan and Germany were intermediate between them. The Stx insertion genotypes of US isolates obtained along a putative transmission chain from cattle, ground beef, clinically ill humans and untreated municipal sewage demonstrated clear differences in distribution, with genotypes associated with human disease found in higher proportions in ground beef and, as expected, clinical isolates. These differing distributions are consistent with differences among EHEC O157 genotypes related to virulence, infectivity and/or environmental survival of this agent.
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Details
- Title
- International comparison of shiga toxin-encoding bacteriophage insertion site genotypes of clinical, bovine and environmental E. coli O157 isolates
- Creators
- Joshua Herbert Whitworth
- Contributors
- Thomas E. Besser (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Veterinary Medicine, College of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525098301842
- Language
- English
- Resource Type
- Thesis