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Title: From osmolytes to diabetes : the impact of sugars and sugar alcohols on the cystic fibrosis pathogen, Burkholderia multivorans
Author: Denman, Carmen Cecile
ISNI:       0000 0004 2744 1842
Awarding Body: University of Exeter
Current Institution: University of Exeter
Date of Award: 2013
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The incidence of CF related diabetes is on the rise as patient life expectancy continues to improve. Sugars elevated in diabetics include glucose, fructose, and mannose. These sugars, in addition to mannitol (recently approved as an inhaled osmolyte) are the basis for this study, aimed at assessing the impact these clinically relevant sugars have on virulence in Burkholderia multivorans. B. multivorans is a member of the Burkholderia cepacia complex (Bcc), and is the most frequent cause of Bcc infection in CF patients. Using an exopolysaccharide-deficient knockout in macrophage and Galleria mellonella infection models, biofilm formation, and adhesion assays, this study has identified exopolysaccharide-dependent and -independent phenotypes. Sequencing of B. multivorans C1576, a CF outbreak isolate, identified three putative adhesins in clinical isolate C1576 but not present in the sequenced environmental strain ATCC17616. Mannitol promoted adhesion and enhanced expression of these adhesins. This study characterised these adhesins and assessed the distribution within other clinical and environmental isolates of B. multivorans and the Bcc. Additionally, transcriptomic profiling of B. multivorans assessed the sugar response and EPS regulation during growth on clinically relevant sugars. Where possible, links were made between phenotypic studies and transcriptome data. B. multivorans EPS derived from fructose and mannitol was subjected to composition analysis using mass spectrometry, and assessed for biological activity. Still relevant to CF related diabetes, the ability of some members of the Bcc to bind insulin was assessed. Results indicated that a minority of strains bound insulin. Furthermore, by using flow cytometry cell sorting and fluorescence microscopy, results also showed only a small number of cells within a given population that bound insulin. In all, this study has added to the knowledge base of B. multivorans but more work is needed to fully understand virulence strategies exploited by this CF pathogen.
Supervisor: Brown, Alan R. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Molecular microbiology ; cystic fibrosis ; insulin ; adhesins ; Burkholderia multivorans ; mannitol ; exopolysaccharide