Chronic infections with Pseudomonas aeruginosa are primarily responsible for the decline in lung function and ultimate mortality in cystic fibrosis patients. The overall aim of this project was to elucidate some of the molecular mechanisms governing the pathogenesis of P. aeruginosa in the cystic fibrosis lung. This was with particular reference to (a) quorum sensing, a cell-to-cell communication system controlling the production of virulence determinants in a population density dependent manner using diffusible signal molecules and (b) the pseudomonas lectins, LecA and LecB, which are known to contribute to biofilm formation. Serial sputum samples were collected from adult and paediatric patients with cystic fibrosis and a cohort of clinical P. aeruginosa isolates was assembled. Using bioreporters, these isolates were shown to synthesise a range of quorum sensing signal molecules. Furthermore, the direct detection of these P. aeruginosa products from infected sputum samples in conjunction with patient clinical data implied an association between sputum quorum sensing signal molecule level and cystic fibrosis disease status, response to intravenous antibiotics and the presence of non-culturable P. aeruginosa. Quorum sensing also makes an important contribution to P. aeruginosa biofilm maturation, antibiotic tolerance and resistance to host defences. There is evidence that the quorum sensing regulated lectins LecA and LecB contribute to biofilm development and this was investigated using different biofilm assays, including the flowchamber biofilm system. This work demonstrated that LecA contributed to biofilm maturation in both laboratory and clinical strains and hydrophobic galactosides were shown to be able to inhibit biofilm development. The putative biofilm target ligand for LecA was tentatively identified as the Psl exopolysaccharide. Mutants deficient in either lecA or lecB produced defective biofilms, which could be inhibited and/or dispersed by galactosides or furanosides respectively, including novel synthetic furanoside dendrimers. The latter proved inhibitory to both laboratory and clinical P. aeruginosa isolates and constitute a potential novel therapeutic.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:514527 |
| Date | January 2009 |
| Creators | Crusz, S. A. |
| Publisher | University of Nottingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://eprints.nottingham.ac.uk/10734/ |
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