Background: C. difficile infection (CDI) after antibiotic use is the most common cause of healthcare-associated diarrhea and colitis. Antibiotic use is the major risk factor for CDI due to loss of specific member(s) of the microbiota that mediate colonization resistance against C. difficile. We have shown that colonization of the gastrointestinal tract by Lachnospiraceae bacteria is associated with decreased severity of clinical signs of disease in a murine model of CDI. We have developed methods to isolate Lachnospiraceae and have characterized the ability of these isolates to decrease the clinical signs of CDI.
Methods: C57BL/6 murine cecal content and tissue was used for Lachnospiraceae isolation. Lachnospiraceae group specific primers were designed and media conditions that enrich for these bacteria were identified. A germ-free murine model of infection was used to identify Lachnospiraceae isolates that can confer colonization resistance and decrease the clinical signs of CDI.
Results: Twenty Lachnospiraceae related to both classified and previously unknown strains were isolated in this screen. The ability of isolates to decrease the clinical signs of CDI was tested using a germ-free mouse model. Germ-free mice infected with C. difficile become moribund by two days post infection whereas monocolonization with a single Lachnospiraceae isolate extended the survival of mice to seven days post infection. Monocolonization with this Lachnospiraceae isolate was also associated with decreased C. difficile toxin activity and colonization levels as well as decreased histopathological changes in the colon.
Conclusions: We isolated previously uncharacterized Lachnospiraceae bacteria and show that one Lachnospiraceae isolate can decrease the clinical signs of CDI in a germ-free mouse model of CDI. Lachnospiraceae isolated in this study will help define factors contributing to resistance against CDI and provide information on the mechanisms by which Lachnospiraceae and other commensal microbes have broadly beneficial effects on the gastrointestinal tract.