Abstract
Urease is an enzyme associated with plants, bacteria, and fungi. It metabolises urea into ammonia, therefore producing a nitrogen source for organisms and altering the pH of their environment. Bacterial infections caused by urease-positive microorganisms have associated urease pathogenicity, for example Proteus mirabilis.The research presented here examines potential new methods for sensing and preventing urease-associated pathogenicity. In Chapter 3 and Chapter 4 a diagnostic sensor to detect impending urinary catheter blockage was optimised and clinically tested in a pilot clinical trial. The diagnostic sensor provides a colorimetric indication that the urinary catheter is more likely to block. The optimised sensor provides an almost 7 h warning prior to blockage, as demonstrated using an in vitro model of a catheterised tract. Furthermore, the sensor is stable in healthy human urine and can be sterilised using ethylene oxide. A small-scale pilot study tested the potential utility of the sensor
in donated urine from long-term catheter users. The sensor correctly predicted the two blockage events and successfully correlated turn-on with the use of bladder maintenance solutions. The microbial composition of the urine donated by the participants was additionally investigated and there was polymicrobial diversity amongst users suffering catheter-associated urinary tract infections.
In Chapter 5, a rational drug discovery technique was employed to identify new urease inhibitors. A targeted approach was developed, whereby published literature was used to develop an in silico screen. Ligands were computationally docked on to the crystal structure of urease, the results were filtered and three compounds tested further in in vitro assays. This approach identified N, N’ -Bis(3-pyridinylmethyl)thiourea as a potent inhibitor to urease and when tested successfully extended the lifetime of a catheter and outperformed the only clinically licensed urease inhibitor: acetohydroxamic acid, when tested in vitro. In Chapter 6, Nasturium officinale extract was examined for its therapeutic benefits against urease. N. officinale is a semi-aquatic plant which contains multiple compounds believed to have therapeutic properties. The extract demonstrated
a dual mechanistic approach to reducing urease pathogenicity. The research presented in this thesis has investigated urease pathogenicity, tested a device to detect its action which could be used by long-term catheter users and investigated various compounds, including a newly identified urease inhibitor and natural products were explored as potential future therapeutics.
| Date of Award | 13 Sept 2023 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Toby Jenkins (Supervisor) & Maisem Laabei (Supervisor) |