The Bordetella Bps Polysaccharide Is Required for Biofilm Formation and Enhances Survival in the Lower Respiratory Tract of Swine

Bordetella bronchiseptica is pervasive in swine populations and plays multiple roles in respiratory disease. Additionally, B. bronchiseptica is capable of establishing long-term or chronic infections in swine. Bacterial biofilms are increasingly recognized as important contributors to chronic bacterial infections. Recently the polysaccharide locusbpsABCDhas been demonstrated to serve a critical role in the development of mature biofilms formed by the sequenced laboratory strain of B. bronchiseptica . We hypothesized that swine isolates would also have the ability to form mature biofilms and thebpsABCDlocus would serve a key role in this process. A mutant containing an in-frame deletion of thebpsABCDstructural genes was constructed in a wild-type swine isolate and found to be negative for poly-N-acetylglucosamine (PNAG)-like material by immunoblot assay. Further, thebpsABCDlocus was found to be required for the development and maintenance of the three-dimensional structures under continuous-flow conditions. To investigate the contribution of thebpsABCDlocus to the pathogenesis of B. bronchiseptica in swine, the KM22Δbpsmutant was compared to the wild-type swine isolate for the ability to colonize and cause disease in pigs. ThebpsABCDlocus was found to not be required for persistence in the upper respiratory tract of swine. Additionally, thebpsABCDlocus did not affect the development of anti- Bordetella humoral immunity, did not contribute to disease severity, and did not mediate protection from complement-mediated killing. However, thebpsABCDlocus was found to enhance survival in the lower respiratory tract of swine.