Combatting Respiratory Pathogens in Cystic Fibrosis: Novel Approaches in Bacterial Targeting, Biofilm Disruption and Sugar Purification

Pseudomonas aeruginosa, Staphylococcus aureus, Burkholderia cepacia and Stenotrophomonas maltophilia frequently establish chronic lung infections in Cystic Fibrosis (CF) patients and engender significant morbidity and, in some cases, death. Partially owing to adaptive mechanisms, including the production of biofilms and virulence factors, these pathogens have developed resistance to conventional antimicrobials. To combat these pathogens, novel interventions are required. This pre-clinical study explores three such approaches. The first approach investigated a novel carbon monoxide releasing molecule (CORM) that had been designed to target the pseudomonal virulence factor, pyocyanin. In vitro testing of this drug, termed pyo-CORM, showed non-specific pyocyanin activation and reduced bacterial growth and biofilm formation in P. aeruginosa, S. aureus and S. maltophilia. The second strategy explored the disruptive capacity of sugar fragments (alginate) against pseudomonal biofilms. We generated and tested alginate fragments, with average degrees of polymerisation within the range of 1-28, against P. aeruginosa PA01 in vitro. Our study found that the fragments were able to perturb growth and disrupt biofilms in PA01 at concentrations exceeding 5 wt% and that smaller fragments were more effective at biofilm disruption than larger fragments. Lastly, this project explored novel purification strategies for the synthesis of sugar-based vaccines using the polysaccharide, and virulence factor, poly-N-acetylglucosamine (PNAG) as a reference. With the aim of improving purity and efficiency in sugar synthesis, this study investigated a photochemical solid phase cleavage method and a selective bead-mediated recovery strategy. These methods, and the design of a continuous UV flow reactor, achieved successful photocleavage and selective recovery of a tagged N-acetylglucosamine (NAG) building block. The results presented in this project highlight the need for ongoing work in these areas. With new treatments will come new adaptations and therefore it is likely that a combination of novel approaches will be key in combatting CF pathogens in the future.