Bacterial factors involved in Escherichia coli O157:H7 colonization of cattle


Sheng, Haiqing.. (2006). Bacterial factors involved in Escherichia coli O157:H7 colonization of cattle. Theses and Dissertations Collection, University of Idaho Library Digital Collections.

Bacterial factors involved in Escherichia coli O157:H7 colonization of cattle
Sheng, Haiqing.
Escherichia coli infections in animals--Testing Cattle--Infections--Testing Escherichia coli O157:H7
Microbiology, Molecular Biology, and Biochemistry
Escherichia coli O157:147 is a common cause of a variety of human illnesses including hemorrhagic colitis and hemolytic uremic syndrome. Cattle are the major reservoir for E. coli O157:147 and the bovine terminal rectal mucosa is a primary site for the bacteria colonization. Strategies to reduce the carriage and prevalence of E. coli O157:147 in cattle can reduce the risk of human exposure to this pathogen. Development of effective intervention strategies to reduce bovine carriage of E. coli O157:147 relies on the understanding of the molecular mechanism of E. coli O157:147 colonization and persistence. We hypothesized that the genes that encode virulence factors involved in human disease may also be important for adherence, colonization, and persistence of E. coli O157:147 in its bovine host. To test this hypothesis, a novel bovine infection model was developed using rectal administration of E. coli O157:117 to establish experimental bacterial colonization of cattle. This infection model was superior to the traditional oral model and produced consistent E. coli O157:147 colonization of cattle. Second, another bovine Shiga toxin-producing E. coli (STEC) - E. coli ONT:H25 which shared the same colonization niche as E. coli O157:147 was identified and characterized. Common virulence factors shared by both E. coli O157:147 and E. coli ONT:H25 included Shiga toxin (Stx), intimin, the translocated-intimin-receptor (Tir), and enterohemolysin were identified. Third, a set of defined deletion mutants of E. coli O157:147 were engineered including: (i) deletions of the virulence factors mentioned above; (ii) deletion of the large plasmid pO157; (iii) deletion of the O antigen. These mutants were systematically tested in vivo using the bovine rectal infection model. The results showed the mutants with deletion of intimin, Tir, the pO157, or the O antigen were shed in lower numbers and for shorter durations compared to the wild-type strain in cattle. This indicated that these bacterial factors enhanced E. coli O157:H7 colonization at the bovine terminal rectal mucosa. In contrast, E. coli O157:H7 that were missing Stx or hemolysin colonized like wild-type. This indicated that Stx or hemolysin was not required for E. coli O157:H7 colonization.
Thesis (Ph. D., Microbiology, Molecular Biology and Biochemistry)--University of Idaho, November 2006.
Major Professor:
Carloyn H. Bohach.
Defense Date:
November 2006.
Format Original:
ix, 171 leaves :ill. ;29 cm.

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