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Title: The reservoir of plasmid-encoded beta-lactamases in commensal aerobic faecal bacteria in Britain and South Africa
Author: Shanahan, Philippa M. A.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1993
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There is increasing evidence to suggest that the normal non-pathogenic commensal flora, of the healthy individual, may act as a reservoir of antibiotic resistant determinants. In order to investigate this potential gene pool further, three commensal faecal flora surveys examining three separate populations have been completed. Firstly, 100 faecal specimens, which had been submitted to clinical diagnostic laboratories from general practitioners in Edinburgh and found not to contain any pathogens, were examined for the presence of antibiotic resistance amongst the lactose-fermenting, aerobic faecal bacteria. A further 100 specimens were obtained from healthy members of the community in Edinburgh and were investigated as before. In developing countries, the carriage of antibiotic resistance amongst pathogens has been reported as being significantly higher than in the developed countries. Consequently, to make such a comparison about non pathogenic commensals, the third survey was carried out in the black communities of South Africa; 361 faecal specimens were obtained and examined for the presence of antibiotic resistant faecal flora. The ampicillin resistant bacteria, from each survey, were purified and investigated further. Conjugation experiments identified the transferability of the resistance determinants. In those strains able to transfer the antibiotic resistance genes, plasmid preparations and restriction profiles were prepared. From such work, the presence of single or epidemic plasmids within the given community could be identified. The causative B-lactamase was determined by analytic isoelectric focusing. The epidemiology of the B-lactamases mediating resistance within this population was thus determined. A follow up survey was carried out in Edinburgh approximately two years after the initial survey. Faecal specimens were obtained from five people who had participated in the 'healthy' commensal flora survey. Previously their specimens were found to harbour transferable ampicillin resistant determinants; the responsible plasmids were isolated and identified. Whether or not ampicillin resistant bacteria had been maintained was assessed prior to investigation of the resistance mechanism employed; persistence of a single plasmid type was sought.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available