A21 ULCERATIVE COLITIS-ASSOCIATED E. COLI PATHOBIONTS POTENTIATE COLITIS IN SUSCEPTIBEL HOSTS.

Abstract Background Ulcerative colitis (UC) is a chronic inflammatory condition linked to intestinal microbial dysbiosis, including the expansion of E. coli strains related to extra-intestinal pathogenic E. coli. These “pathobionts” exhibit pathogenic properties, but their potential to promote UC is unclear due to the lack of relevant animal models. Aims We explored the potential to establish a mouse model of GI infection by the UC-associated E. coli strain p19A, as well as characterize the pathogenic features of p19A. Methods We used a representative UC pathobiont strain (p19A), and mice lacking single immunoglobulin and toll-interleukin 1 receptor domain (SIGIRR), a deficiency increasing susceptibility to gut infections. Vancomycin-pretreated Sigirr-/- mice were subsequently gavaged with the control E. coli DH10B (a derivative of commensal strain K-12) or p19A. One day after infection, mice were exposed to 2.5% dextran sodium sulfate (DSS) in their drinking water for another 4 days. Results Strain p19A was found to adhere to the cecal mucosa of Sigirr-/- mice, causing modest inflammation. Moreover, it dramatically worsened DSS-induced colitis. This potentiation was attenuated using a p19A strain lacking α-hemolysin genes, or when we targeted pathobiont adherence using a p19A strain lacking the adhesin FimH, or following treatment with FimH antagonists. Conclusions Thus, UC pathobionts adhere to the intestinal mucosa, and worsen the course of colitis in susceptible hosts in a manner dependent on specific virulence factors, including α-hemolysin and FimH. Funding Agencies CCC, CIHR