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Title: Studies on Escherichia coli O157:H7 in sheep
Author: Wales, Andrew Derek
ISNI:       0000 0001 3551 179X
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2002
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Escherichia coli 0157: 1-17is a significant human pathogent hat persistsi n asymptomatic animal hosts. It forms a characteristic attachment, the attaching-effacing (AE) lesion, on cell monolayers in vitro and in the intestine in some animal models. Cattle and sheep are asymptomatic carriers of E. coli 0157: H7 and sources of the organism for humans. The present studies examined the persistence of several strains of E. coli 0157: H7 in orally inoculated sheep, and attempted to correlate persistence with features of the strains in vitro and in vivo. A particular hypothesis tested was that adhesion of the bacterium to the intestinal mucosa is a significant mechanism for persistence in animal hosts. Host- and strain-dependentv ariation in the persistente xcretion of E. cola 0157: H7 was observed. Correlations could not be discerned between the persistence of the various bacterial strains and the results of a range of phenotypic tests. The ability of E. coli 0157: H7 to form AE attachments to the large intestinal mucosa in sheep of up to six months of age was demonstrated. No consistent site of persistence of E. coli 0157: H7 within the ovine alimentary tract was found, and AE lesions were not detected in sheep which were persistently excreting the organism. However, commensal bacteria, including E. coli 026, were seen to have formed AE attachments on the large intestinal mucosa. It was concluded that the attachment of E. coli 0157: H7 to the large intestinal mucosa by AE lesion formation may have a role in persistent carriage, but that persistence of the bacterium in the ovine intestine is probably influenced by additional bacterial and host factors. The potential value of interference in the formation of AE lesions, to reduce the prevalence of E. coli 0157: H7 excretion by sheep and other ruminants, merits further investigation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Microbiology