Impact of polymicrobial interactions and within-host adaptation on CAUTI pathogenesis - Project Summary/Abstract Urinary tract infection (UTI) is one of the most common infections worldwide and a leading cause of morbidity and healthcare expenditures across all ages. Older adults and individuals with catheters have a particularly high risk of UTI sequelae, including kidney infection, permanent renal damage, and urosepsis. The average mortality rate for urosepsis is 20-40%, but ranges as high as 66% for patients with catheter-associated UTI (CAUTI). Catheterization also promotes persistent polymicrobial colonization and infection by a wide range of understudied microbes, including multidrug-resistant organisms that threaten the utility of last-resort antibiotics. There is a substantial gap in knowledge regarding the impact of microbe-microbe interactions and within-host adaptation on progression from initial colonization to urosepsis and development of antimicrobial resistance. Our preliminary data demonstrates that the three most common and persistent colonizers of the catheterized urinary tract are Enterococcus faecalis, Proteus mirabilis, and Escherichia coli, with some patients being co-colonized by all three species for up to 6 months. We further demonstrate that dual-species interactions involving these species enhance formation of recalcitrant catheter biofilms and increase infection severity in a mouse model of CAUTI. However, it is not yet known how all three species interact under physiologically-relevant conditions, nor the impact of their interactions on biofilm formation and CAUTI pathogenesis. We have further determined that P. mirabilis accumulates phenotypic and genotypic changes during persistent colonization of the urinary tract, many of which are likely to alter pathogenic potential as well as fitness within a polymicrobial community. We hypothesize that the interactions between P. mirabilis, E. coli, and E. faecalis will alter i) biofilm architecture, composition, and antimicrobial resistance, ii) stimulation of the innate immune response, and iii) incidence of disseminated infection and urosepsis. We further hypothesize that within-host adaptation during persistent colonization will promote biofilm formation and bladder colonization but decrease incidence of severe disease, and will also select for greater codependence among co-colonizing isolates, thereby modifying polymicrobial interactions. In Aim 1, we will determine the impact of polymicrobial interactions and inoculation order on bacterial viability, transcription profiles, and biofilm composition in an “artificial bladder model” and on colonization, immune stimulation, and infection progression in a mouse CAUTI model. In Aim 2, we will identify genotypic and phenotypic changes that occur in all three species during persistent colonization and examine contribution to biofilm formation, CAUTI severity, and polymicrobial interactions. The long-term objective of the proposed studies is to identify new targets for preventing or disrupting the formation of recalcitrant polymicrobial biofilms and to inform treatment strategies for catheterized patients with persistent polymicrobial bacteriuria.
