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Title: Antimicrobial strategies against Burkholderia cepacia
Author: Maxwell, Alison Irene
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2000
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The aim of this project was to investigate novel antimicrobial strategies against B. cepacia, based on natural antimicrobial compounds present in plants and human airways as protection against bacterial disease. The project focused on a panel of 20 strains of B. cepacia complex. Isolates included strains representing major epidemic clones of B. cepacia and exhibiting a range of susceptibilities to all classes of conventional antibiotics. The project is focused on two major themes. First, a study of antimicrobials from plants and second, examination of the antimicrobial activities of cationic peptides present in human airway secretions. The susceptibility of the B. cepacia strain panel to plant extracts was investigated, in particular the activity of aqueous garlic extract (AGE) and thyme oil. The MIC of thyme oil for all 20 strains was found to be 0.01%. MICs of AGE ranged from 0.25%-3%. Killing curves suggesting that AGE produces a slow killing effect over a twenty four hour period, whereas thyme oil kills bacterial cells in less than 20 minutes. By electron microscopy, no intact bacteria were observed after three minutes incubation with thyme oil. In contrast, two hours incubation with AGE produced morphological changes in the cellular structure of B. cepacia consistent with much slower damage to the bacterial cell membrane. Attempts were then made to purify and identify the chemical nature of the antimicrobial agents using reverse phase HPLC. AGE was shown to contain allicin along with other anti-cepacia compounds. Thyme oil was shown to comprise the phenols thymol and its isomer, carvacrol. Human (hBD-1) and murine (mBD-1) b-defensins were examined for activity against B. cepacia. In contrast to the salt-sensitive antimicrobial activity observed with Pseudomonas aeruginosa, no antimicrobial activity was observed against strains of B. cepacia.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available