Detection and elimination of a novel non-toxigenic strain from the microbiota of a mouse colony.

is an enteric bacterial pathogen that can a cause nosocomial infection leading to debilitating colitis. The development of a murine model of infection has led to fundamental discoveries in disease pathogenesis and the host immune response to infection. Recently, endogenously present in the microbiota of mice has been reported and was found to complicate interpretation of mouse studies. Here, we report a novel strain, named NTCD-035, isolated from the microbiota of our mouse colony. The presence of NTCD-035 in mice prior to challenge with a highly pathogenic strain (VPI10463) led to significantly reduced disease severity. Phylogenetic characterization derived from whole genome sequencing and PCR ribotyping identified the isolate as a novel clade 1, ribotype 035 strain that lacks the pathogenicity locus required to produce toxins. Deficiency in toxin production along with sporulation capacity and secondary bile acid sensitivity was confirmed using assays. Inoculation of germ-free mice with NTCD-035 did not cause morbidity despite the strain readily colonizing the large intestine. Implementation of a culture-based screening procedure enabled the identification of mice harboring in their microbiota, the establishment of a -free mouse colony, and a monitoring system to prevent future contamination. Taken together, these data provide a framework for screening mice for endogenously harbored and support clinical findings that demonstrate the therapeutic potential of non-toxigenic strains in preventing associated disease. : - Pathogenicity locus, - Colony forming units, - toxin-A, - toxin-B, binary toxin A, binary toxin B, binary toxin R, non-toxigenic .