Catalase Activity is Critical for Proteus mirabilis Biofilm Development, Extracellular Polymeric Substance Composition, and Dissemination during Catheter-Associated Urinary Tract Infection.

Proteus mirabilis is a leading uropathogen of catheter-associated urinary tract infections (CAUTIs), which are among the most common health care-associated infections worldwide. A key factor that contributes to P. mirabilis pathogenesis and persistence during CAUTI is the formation of catheter biofilms, which provide increased resistance to antibiotic treatment and host defense mechanisms. Another factor that is important for bacterial persistence during CAUTI is the ability to resist reactive oxygen species (ROS), such as through the action of the catalase enzyme. Potent catalase activity is one of the defining biochemical characteristics of P. mirabilis, and the single catalase () gene in strain HI4320 was recently identified as a candidate fitness factor for UTI, CAUTI, and bacteremia. Here, we show that disruption of results in increased ROS levels, increased sensitivity to peroxide, and decreased biofilm biomass. The biomass defect was due to a decrease in the production of extracellular polymeric substances (EPS) by the mutant and specifically due to reduced carbohydrate content. Importantly, the biofilm defect resulted in decreased antibiotic resistance and a colonization defect during experimental CAUTI. The mutant also exhibited decreased fitness in a bacteremia model, supporting a dual role for catalase in P. mirabilis biofilm development and immune evasion.