The Indigenous Gut Microbiota Mediates Colonization Resistance Against Clostridium difficile.

Abstract

Clostridium difficile is a pathogen that causes nosocomial antibiotic-associated diarrhea and colitis. The indigenous gastrointestinal (GI) microbiota plays an important role in protecting the host against infection with C. difficile. Administration of antibiotics disrupts the GI microbiota thus allowing for C. difficile to colonize and cause disease. The overall goal of this project was to understand the relationship between antibiotic administration and the role of specific members of the indigenous GI microbiota in mediating colonization resistance against C. difficile. Mice were treated with two different antibiotic regimens to make them susceptible to experimental C. difficile infection (CDI). Clinical signs of disease such as weight loss, diarrhea and hunched posture were monitored and at necropsy, tissue was harvested for histopathologic and culture-independent analysis of the gut community. Results from these experiments demonstrate that antibiotic administration is associated with major shifts in the microbial GI community structure that predispose mice to CDI. Specifically, antibiotic-treated mice challenged with C. difficile strain VPI 10463 either developed rapidly lethal CDI or were stably colonized with mild disease. The GI microbiota of animals with mild disease was predominated by bacteria from the family Lachnospiraceae, resembling the baseline community, while the GI community of animals with severe disease was predominated by Escherichia coli. To test the hypothesis that Lachnospiraceae was less permissive to C. difficile colonization than E. coli, both Lachnospiraceae and E. coli members were isolated from wild-type mice and tested in germ-free mice. Results from these experiments indicate that a single Lachnospiraceae isolate (D4), but not E. coli, partially restored colonization resistance against C. difficile and improved clinical CDI. Thus, understanding how members of the indigenous GI microbiota, specifically Lachnospiraceae, interfere with C. difficile colonization could lead to new modalities for prevention and treatment of this important infection.