The role of sugar transport in C. difficile colonization and disease

Project Summary/Abstract Clostridioides difficile infection (CDI) is still the most common cause of healthcare-associated infection despite a concerted effort to reduce the incidence. Increasingly, C. difficile is found in the community among persons with no recent healthcare contact. The long-term goal of this project is to identify novel therapeutic targets which can be exploited to treat CDI and control the spread of C. difficile. The overall objectives in this application are to (i) elucidate the specificity and redundancy of the sugar transporters under positive selection in C. difficile, (ii) determine their role in disease, and iii) examine the impact of dietary sugar on asymptomatic carriage. The central hypothesis is that C. difficile has evolved to better occupy niche space within the gastrointestinal tract (GIT) by taking advantage of the modern sugar-rich diet. The rationale for this project is that determining the specificity and importance of sugar transporters and downstream metabolism in C. difficile carriage and infection sets up a robust scientific framework whereby new prophylaxis and treatment strategies can be developed. The central hypothesis will be tested by pursuing three specific aims: 1) Elucidate the specificity, redundancy, and influence on toxin production of evolving sugar transport genes, 2) Determine the effect of evolving sugar transport genes on community invasion and disease, and 3) Investigate the role of sugars in niche establishment and asymptomatic carriage. Under the first aim, clean deletions of sugar transporters previously shown to be under positive selection in epidemic C. difficile will be generated and their effect on growth and toxin production assessed. The second aim will determine the role of sugar transport in invasion using a novel in vitro bioreactor assay and disease by utilizing a mouse model of CDI. Finally, aim three will assess the role of sugar availability in asymptomatic C. difficile colonization by using toxin negative C. difficile strains and a novel 13 strain mouse microbiota colonization model. The research proposed in this application is innovative, because it focuses on the metabolic adaptation of C. difficile to carbohydrates and their role in asymptomatic carriage as well as disease. This focus has the potential to lead to novel prophylactic strategies that can be used against C. difficile before the emergence of the disease. The proposed research is significant as it will provide a solid scientific justification for the continued examination of metabolism as a virulence mechanism in C. difficile and provide a framework for the future study of novel prophylactic, intervention, and treatment options.