serovar 9 responses to elevated temperature and co-culture with .

and  are commensal organisms that can shift from a benign to pathogenic state and cause severe disease in swine. We hypothesized that a change in host temperature and/or interactions with  could impact  growth dynamics. We compared phenotypic properties of a clinical  serovar 9 strain (SS9C) with clinical serovar 2 and healthy serovar 9 isolates grown at 37 and 41 °C. We further investigated how co-culturing with  affected biofilm formation of SS9C. Crystal violet staining indicated that SS9C produced significantly more biofilm than the other strains when grown at 37 °C; this difference was amplified at 41 °C. However, cell counts did not increase at the higher temperature. Biofilms of SS9C at 37 and 41 °C were unaffected by DNase I digestion, while other strains were both susceptible at 41 °C. All biofilms were susceptible to proteinase K and α-amylase digestion at both temperatures. We showed that growth at 41 °C increased biofilm formation and shifted the phenotype of SS9C; however, neither increased temperature nor co-culture with  increased planktonic or sessile cell counts. Our study suggests that increased temperature in the host may be an important factor in understanding  disease development.