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Type: Thesis
Title: Characterisation of biofilms in chronic rhinosinusitis and its clinical and immunological consequences.
Author: Foreman, Andrew
Issue Date: 2011
School/Discipline: School of Medicine
Abstract: The research contained within the PhD thesis investigates the role of biofilms in chronic rhinosinusitis (CRS). Following an exhaustive literature review of CRS aetiology, pathogenesis and microbiology, the key deficiencies in our understanding of this disease were highlighted; with particular attention paid to potential role biofilms might play in this disease. It was clear from the literature that the issue of the common biofilm-forming organisms in CRS was incompletely understood and that if this was clarified, it could then be used as a basis for more species-specific investigation of biofilms in CRS. Adopting a species-specific approach may facilitate the development of targeted, novel anti-biofilm strategies that could be employed to improve the outcomes of our most recalcitrant patients. This research investigation commenced with a study to directly correlate a newly developed Fluorescence in situ Hybridisation (FISH) protocol with the current gold standard- BacLight staining imaged on the confocal scanning laser microscope (CSLM). Not only did this project validate FISH as a tool for biofilm identification in CRS but also it also clearly elucidated the research scenarios in which each of these complementary techniques could be used. This will assist to guide future research. A larger cohort study then identified S. aureus as the most common biofilm-forming organism in an often polymicrobial mix that may contain fungal biofilms. The clinical relevance and immunological consequences of biofilm characterisation were then explored. A retrospective clinical investigation found that patients with unimicrobial H. influenzae biofilms had mild disease that was highly responsive to current treatment strategies. In contrast, patients with S. aureus biofilms whether alone or in association with other species had severe disease and poor evolution after surgery. These results suggest that in CRS, not all biofilms are the same. Investigating the immunological consequences of biofilm characterisation in CRS also separated out the two common biofilm-forming organisms H. influenzae and S. aureus. H. influenzae biofilms were not associated with a particular skewing of the T-helper adaptive immune response or a release of superantigens. However S. aureus biofilm interact with the immune system both directly, with a skewing of the T cell response towards the T-helper₂ cascade and a subsequent eosinophilic inflammation, and indirectly via dispersing planktonic clones that may release superantigens into the sinuses. Importantly this study was also able to differentiate the effect of superantigens and S. aureus biofilms by discovering that superantigens act via IgE induction whereas S. aureus biofilms skew the Thelper response towards the T-helper₂ pathway with elevated IL-5, ECP and TGF-β1 being characteristic of their presence. This novel discovery high-lights a potential independent role for S. aureus biofilms in CRS pathogenesis, providing a link between biofilms and disease for the first time. Finally, with an eye to the future, we developed a novel, non-invasive diagnostic test for S. aureus biofilms. We were able to achieve this via detection of the exopolysaccharide matrix component poly-N-acetylglucosamine (PNAG). PNAG is essential for biofilm formation by S. aureus and its detection allows us to differentiate between purely planktonic cultures of this organism and the more quiescent biofilm form, which may escape detection by routine microbiological testing, but has been demonstrated already to be associated with severe, surgically recalcitrant disease. The development of this test requires further testing but will ultimately be able to diagnose S. aureus biofilms without the need for mucosal biopsies, allowing pre- and post-operative biofilm detection to guide directed and aggressive antibiofilm treatment strategies.
Advisor: Wormald, Peter-John
Dissertation Note: Thesis (Ph.D.) -- University of Adelaide, School of Medicine, 2011
Keywords: biofilms; chronic rhinosinusitis; S. aureus; fish; outcomes
Provenance: Copyright material removed from digital thesis. See print copy in University of Adelaide Library for full text.
Appears in Collections:Research Theses

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