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Title: The relationship between plasmid presence, antibiotic resistance and surface structures in Bacteroides
Author: Hamilton, Michelle Ann Elizabeth
ISNI:       0000 0001 3528 4865
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1988
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One hundred and fifty -one Bacteroides isolates were collected from a variety of clinical samples (wound, swabs, vaginal swabs and blood cultures) and from the cervix of women attending a colposcopy clinic. A method for the isolation of plasmid DNA from Bacteroides species was developed and provided a simple and reproducible technique for the analysis of the plasmid content of the isolates. The strains were divided into three groups, the B. fragilis group, the melaninogenicus /oralis group and the asaccharolytic group. The incidence of plasmids in each group was determined. Forty per cent of the strains were found to have plasmids but there was great variation in the plasmid distribution within each group. Sixy -one percent of the B. fragilis strains had plasmids as opposed to 23% of the asaccharolytic Bacteroides, and 10% of the melaninogenicus /oralis strains. Plasmids ranging in size from 1.1 to 108 MegaDaltons (MDa) were detected but most of the plasmids were less than 10 MDa. Seventy -nine percent of the plasmid- containing strains had more than one plasmid. The susceptibility of the isolates to chloramphenicol, clindamycin, metronidazole, erythromycin, imipenem, moxalactam, cefoxitin, cefotetan, cefotaxime, cefuroxime, penicillin and nalidixic acid was investigated. Chloramphenicol was the most active non -beta -lactam antibiotic. Six percent of the strains were resistant to clindamycin and metronidazole resistance, though rare, was observed in 2% of the strains. Among the beta -lactam antibiotics, imipenem, though not in use in the United Kingdom was found to have excellent activity against the Bacteroides. Moxalactam and cefoxitin were also very active with less than 1% of the strains displaying resistance. Various levels of resistance, ranging from 4 to 50% were found amongst the three Bacteroides groups. There was evidence of species variation in antimicrobial susceptibility. Attempts were made to correlate plasmid presence with observed antibiotic resistance and capsule variation within the strains. Transferable macrolide -lincosamide -streptogramin (MLS) resistance determinants were not identified and observed MLS resistance could not be cured. However, a possible correlation was found between plasmid content and resistance to cefoxitin but plasmid content was not found to alter the resistance pattern of strains to nalidixic acid. Capsule variation was found to depend on altered gene expression and not on the presence or absence of plasmids.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Plasmids in bacteroides