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dc.contributor.authorYates, Catherine Maryen
dc.date.accessioned2018-05-14T10:17:05Z
dc.date.available2018-05-14T10:17:05Z
dc.date.issued2005en
dc.identifier.urihttp://hdl.handle.net/1842/30050
dc.description.abstracten
dc.description.abstractIn animals, the study of antibiotic resistance in bacteria has been focused on organisms that are pathogenic in human or animal hosts. The development of antibiotic resistance in commensal bacteria is also of concern because they may act as a reservoir ofresistance genes. This thesis aimed to determine levels of resistance to veterinary and medical antibiotics in the commensal Escherichia coli of calves, to explore the genotypic diversity of isolates, and to study the molecular mechanism and transfer dynamics ofresistance to apramycin.en
dc.description.abstractThe antibiotic sensitivity testing of calf faecal E. coli, obtained by weekly sampling, demonstrated that there was resistance to beta-lactams, cephalosporins, streptomycin, trimethoprim, chloramphenicol, tetracycline and sulphamethoxazole. These resistance phenotypes had not been selected for on antibiotic-containing media, indicating a high prevalence of the corresponding resistance determinants.en
dc.description.abstractFive hundred and forty three isolates were genotyped by pulsed-field gel electrophoresis. Examination of the patterns generated by restriction with Xbal and analysed with BioNumerics software revealed a total of 55 different genotypes. Ampicillin resistant isolates were more diverse (24 genotypes) than apramycin or nalidixic acid resistant isolates (5 and 2 genotypes respectively). Apramycin resistance (aprR) was conferred by three conjugative plasmids, pUK2001, pUK2002 and pUK2003, of sizes 91, 115 and 181Kb respectively. All aprR plasmids conferred cross-resistance to the medical antibiotics tobramycin and gentamicin. Plasmids pUK2002 and pUK2003 also carried tetracycline and streptomycin resistance. Plasmid pUK2001 demonstrated very high transfer frequencies (4.12x10" during 7 hrs mating), horizontal spread to three different genotypes, and an apparent fitness advantage in vitro.en
dc.description.abstractThis thesis shows a very high prevalence of antibiotic resistance genes in the commensal faecal flora of food-producing calves. This may have significant implications for the transmission ofresistance genes to human clinical bacteriaen
dc.publisherThe University of Edinburghen
dc.relation.isreferencedbyAlready catalogueden
dc.subjectAnnexe Thesis Digitisation Project 2018 Block 18en
dc.titleMolecular epidemiology of antibiotic resistance in the commensal Escherichia coli of calvesen
dc.typeThesis or Dissertationen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnamePhD Doctor of Philosophyen


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