The significant effects of butyrate on Clostridioides difficile fitness and pathogenesis - PROJECT SUMMARY/ABSTRACT The Centers for Disease Control and Prevention classifies Clostridioides difficile (Cd) as an urgent threat to the nation's health, as it causes 450,000 infections, 15,000 deaths, and 1 billion dollars in excess healthcare costs per year in the United States. The status quo as it pertains to treating Cd infections (CDIs) is antibiotic use and, in recurrent cases, microbial replacement therapy (MRT). Antibiotics contribute to antibiotic resistance and recurrent CDIs. Although MRTs (e.g., defined consortia of microbes or fecal transplant) are increasingly accessible, the long-term sustainability and accessibility of these treatments remain to be determined. These limitations highlight the need for new and more precise strategies for coping with CDI. Because a disrupted (dysbiotic) gut microbiome is the primary risk factor for CDI, a better understanding of the interactions between Cd, the microbiome, and the host will aid development of such treatments. However, against the backdrop of the complex microbial and metabolic milieus of the gut, a major challenge is to identify the interactions that merit deeper investigation and eventual therapeutic targeting. Diet is emerging as a significant risk factor for CDI. In particular, dietary fiber can improve CDI in animal models and high fiber intake in humans is associated with lower odds of Cd colonization. However, there remains an unmet, critical need for a mechanistic understanding of how dietary fiber (and the related impacts on the microbiome) affect CDI. The overall objective of this grant application is to gain a better understanding of how butyrate impacts Cd. Butyrate is a prominent microbiome- host co-metabolite that is influenced by host dietary fiber intake and differentiates healthy from dysbiotic gut ecosystems. Based on our preliminary data and the work of others, our central hypothesis is that butyrate is a key determinant of Cd fitness and pathogenesis during CDI. In the proposed work, we will address our central hypothesis through three independent aims. We will use methods including bacterial cell culture, bacterial genetics, proteomics, metabolomics, transcriptomics, ribosome profiling, a variety of molecular biology techniques, and conventional/gnotobiotic murine models of CDI. Our study team is uniquely poised to use these methods to define mechanisms by which butyrate impacts Cd sporulation & toxin production/release and to determine the direct effects of butyrate on Cd fitness and pathogenesis in mice. The proposed work will therefore significantly advance our understanding of how butyrate impacts CDI. The work is aligned with our long-term goal to define key aspects of Cd biology and to develop new concepts and approaches for excluding Cd from the gut. Our results are expected to have an important positive impact, as they will be a foundation for developing targeted treatments distinct from antibiotics or MRT (e.g., dietary intervention, precision probiotics, or new Cd/microbiome-targeting drugs) to mitigate CDI in at-risk human populations.
