Proteus mirabilis RTX proteins: Role in polymicrobial biofilm formation and pathogenesis of catheter associated urinary tract infection

Project summary/abstract Catheter-associated urinary tract infections (CAUTI) are among the most common nosocomial infections and are often caused by Proteus mirabilis. CAUTIs are also often polymicrobial, and the most common and persistent co-colonizing partners are P. mirabilis and Enterococcus faecalis. Polymicrobial CAUTIs are typically more severe and associated with increased patient risk, treatment failure, and secondary bacteremia. The prevalence of co-colonization of P. mirabilis with and E. faecalis combined with the increased severity of disease suggest that disrupting polymicrobial interactions between these species could be beneficial for enhancing treatment efficacy. There is a fundamental gap in knowledge in current understanding of mechanisms and clinical relevance of polymicrobial interactions with respect to CAUTI progression and disease severity. Addressing this gap has the potential to inform development of novel therapeutics to disrupt disease- enhancing interactions and guiding best practices for clinical interventions. Our preliminary data indicate that polymicrobial biofilms formed by P. mirabilis and E. faecalis exhibit increased biomass and antibiotic resistance and revealed P. mirabilis RTX proteins as the most enriched factor in the polymicrobial biofilm. The central hypothesis of this proposal is that P. mirabilis RTX proteins form an integral structural component of the polymicrobial biofilm and mediate aggregation with other uropathogens, thereby contributing to the establishment and severity of polymicrobial CAUTI. We will address this hypothesis by completing two specific aims: 1) Examine the expression of P. mirabilis RTX proteins during polymicrobial biofilm formation and determine their contribution to biofilm architecture, adhesion, and mediating bacteria-bacteria interactions. 2) Determine the contribution of P. mirabilis RTX proteins to pathogenesis of polymicrobial CAUTI. In terms of the first aim, the role of P. mirabilis RTX proteins in polymicrobial biofilms are already underway utilizing the clinically relevant P. mirabilis HI4320 strain. The media conditions, time-scale, and polymicrobial mixtures in which P. mirabilis RTX proteins mediate attachment to abiotic and biotic surfaces and biofilm formation will be determined utilizing traditional 24-well plate biofilm assay and the more physiologically-relevant glass bladder model. A major training goal of this project is the implementation of high-resolution microscopy techniques to examine spatial distribution of bacteria within polymicrobial catheter biofilms. Together, this aim will provide insight into the role of P. mirabilis RTX proteins in polymicrobial biofilms as well as development of a new protocol for visualizing intact biofilms on clinically relevant surfaces. For the second aim, the established mouse model of CAUTI will be utilized to determine the role of P. mirabilis RTX proteins in establishment, persistence, and pathogenesis of polymicrobial CAUTI. The proposed research is significant because it will illuminate a mechanism through which common uropathogens interact with each other to establish persistent colonization, both on catheter surfaces and within a relevant host model. This knowledge can be leveraged to find develop novel compounds capable of disrupting these disease-promoting interactions to improve patient outcomes and reduce the healthcare cost and burden of CAUTI.