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Title: Diagnostic and therapeutic approaches for the control of catheter-associated urinary tract infection
Author: Milo, Scarlet
ISNI:       0000 0004 7961 3917
Awarding Body: University of Bath
Current Institution: University of Bath
Date of Award: 2019
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This research aims to investigate four novel approaches to the detection and prevention of catheter encrustation and blockage following infection by the Gram-negative, motile bacterium Proteus mirabilis (P. mirabilis). Expression of a potent bacterial urease elevates urinary pH, leading to the local supersaturation and precipitation of mineral deposits from the urine that occludes urine-flow through the catheter. Vesico-ureteric reflux following blockage by crystalline biofilms may result in serious symptomatic episodes such as pyelonephritis, endotoxic shock and septicaemia. Three of the four described approaches for the management of catheter-associated urinary tract infection employ a dual-layered polymeric delivery system, in which a lower poly(vinyl alcohol) reservoir layer contains either a diagnostic (5(6)-carboxyfluorescein) or therapeutic (lytic bacteriophage) cargo. The hydrogel layer is capped and sealed by an upper layer of the pH-responsive polymer poly(methyl methacrylate-co-methacrylic acid) (Eudragit S100®). Alkalinisation of local urine media (pH >7) induces degradation of the Eudragit layer, thus releasing the contained cargo. Release of 5(6)-carboxyfluorescein results in a clear and unambiguous colour change to give advance warning (up to 14.5 hours) of impending catheter blockage, whilst bacteriophage release increased time to catheter blockage by 100% (13 hours to 26 hours).The final approach describes the formulation and development of a novel small-molecule urease inhibitor, 2-mercaptoacetamide (2-MA), for the prevention of crystalline biofilm formation. Inhibition of bacterial urease without inducing bacterial cell death allows for the 'disarming' of P. mirabilis without directing population evolution via initiation of a selective pressure. Comparison of 2-MA with the approved drug acetohydroxamic acid (AHA) allows for direct evaluation against the current 'gold standard' in treatment of chronic urea-splitting infection. All approaches were evaluated for clinical efficacy within a physiologically representative model of the catheterised tract. In vitro bladder models were formulated to emulate late-stage infection by uropathogenic clinical isolates (initial inoculum 108 CFU/mL), such that preventative strategies were evaluated under 'worst-case scenario' conditions. Performance within in vitro systems inoculated with P. mirabilis was directly compared to urease-negative Escherichia coli (E. coli), to assess uropathogenic specificity. Translation of these approaches into a clinical environment may allow a multifaceted approach to the detection and prevention of catheter blockage; a problem for which there is currently no effective control method.
Supervisor: Bull, Steven ; Jenkins, Andrew Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available