Harnessing polymicrobial interactions in the catheterized urinary tract to identify novel inhibitors of Proteus mirabilis urease activity

Project Summary Catheter-associated urinary tract infection (CAUTI) is the leading cause of secondary nosocomial bloodstream infections. Urease-producing organisms such as Proteus mirabilis are common causes of CAUTI and associated with numerous complications. Urease hydrolyzes urea to ammonia, which raises the urine pH and causes precipitation of ions into crystals, ultimately leading to catheter encrustation and blockage and urinary stone formation and increasing the risk of bacteremia, sepsis and death. The only urease inhibitor approved by the Food and Drug Administration (FDA), acetohydroxamic acid (AHA), shows efficacy in preventing urinary stone formation but has severe side effects that limit its clinical use. Therefore, alternative strategies are needed for targeting bacterial urease activity to prevent catheter encrustation and stone formation. In patients with long-term indwelling catheters, CAUTI is often polymicrobial. As demonstrated in our prior publications and preliminary data, we found that common constituents of polymicrobial CAUTI secrete molecules that modulate P. mirabilis urease activity and infection severity. We therefore performed untargeted global metabolomics analysis on cell-free supernatants of urease-modulating bacterial strains and identified 36 candidate urease dampening metabolites. We validated the activity of four compounds: histamine (CAS 51-45- 6), leucylglycine (CAS 686-50-0), phenylpyruvate (CAS 156-06-9) and imidazole lactate (CAS 14403-45-3). Our preliminary data suggests that leucylglycine and imidazole lactate dampen urease activity, at least in part, by acting directly on the urease active site. In contrast, histamine and phenylpyruvate appear to indirectly inhibit urease activity through an uncharacterized mechanism. The goal of this NRSA F30 proposal is to determine the mechanism of action of urease modulation and conduct pre-clinical assessment of the therapeutic potential of these dampening compounds. Aim 1 will determine the mechanism of indirect urease modulation for histamine and phenylpyruvate and explore whether compounds of different mechanisms of action have synergistic effects on urease activity when administered in combination against a panel of urease- producing pathogens. Aim 2 will assess the translational potential of dampening compounds for preventing Foley catheter encrustation, crystalline biofilm formation, and blockage. The experiments outlined in this proposal will provide a framework for harnessing polymicrobial interactions for drug discovery and the development of novel therapeutics to prevent CAUTI associated morbidity and mortality. This work will take place at the Jacobs School of Medicine and Biomedical Sciences in the laboratory of Dr. Chelsie Armbruster, who is an expert in CAUTI and microbial pathogenesis research. The training plan is tailored for my development as a physician-scientist in the field of infectious disease, and includes mentoring by successful physician-scientists and clinical preceptorships in infectious disease and internal medicine.