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Title: Physiology and antibiotic susceptibility of mycobacterial biofilms
Author: Lethbridge , Samuel Aston
ISNI:       0000 0004 7427 1292
Awarding Body: St George's, University of London
Current Institution: St George's, University of London
Date of Award: 2018
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Treatment of tuberculosis requires months of antimycobacterial therapy. This tolerance to antibiotics displayed by Mycobacterium tuberculosis could be attributed to biofilm formation. Biofilms are the cause of many chronic infections. The aim of this thesis was to apply laboratory methods for the culture of Mycobacterium smegmatis and M. tuberculosis H37Rv biofilms and to further characterise these bacterial phenotypes in terms of their physiology, gene expression and drug susceptibility The Modified Robbins Device (MRD) and the Constant Depth Film Fermenter (CDFF) laboratory models were applied alongside the previously established well-plate pellicle model. Antibiotic efficacy studies of M. tuberculosis pellicles identified drug-tolerant bacteria. These pellicle biofilms exhibited tolerance to rifampicin and isoniazid many times above the planktonic minimum inhibitory concentration (MIC). CDFF biofilms were tolerant to a planktonic MIC of isoniazid. CDFF and pellicle biofilms of M. tuberculosis and pellicle biofilms of M. smegmatis were investigated in terms of their gene expression using microarrays to determine the underpinning molecular mechanisms behind biofilm formation Biofilms of both mycobacterial species upregulated lipid metabolism and biosynthesis. M. tuberculosis biofilms upregulated genes involved in the type seven secretion system (T7SS) and genes which code for PE/PPE proteins. T7SS is known to interact with some PE/PPE proteins, many of which are cell-surface associated. These gene expression profiles suggested significant restructuring of the cell wall and provides a genetic basis for extra-cellular matrix formation. Also, low levels of metabolic activity were identified within these biofilms using fluorescent staining with viability dyes and flow cytometry. Overall, this thesis provides a controlled method for mycobacterial biofilm formation using the CDFF and confirms that M. tuberculosis H37Rv biofilms comprise antibiotic tolerant cells.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available