Clostridium difficile, a major nosocomial pathogen is the principal causative agent of antibiotic associated diarrhea and pseudomembranous colitis. The toxigenic C. difficile strains that cause disease secrete virulence factors, toxin A and toxin B, which are responsible for colonic injury and inflammation. C. difficile toxins have no export signature and are secreted by an unusual mechanism that involves TcdE, a holin-like protein. Like other channel forming proteins, TcdE exists as the oligomer in C. difficile membrane. The preliminary study found tcdE mRNA to contain multiple start-codons that translate into three different isoforms. It was also noted that tcdE over-expression in bacteria causes membrane damage. Based on these observations, it was hypothesized that TcdE content in C. difficile is highly controlled through various regulatory mechanisms.
Aim 1 of this application will determine how transcription of a tcdE gene is regulated and will also study the regulatory mechanisms involved in the translation control of tcdE mRNA into different TcdE isoforms.
Aim 2 will determine the importance of TcdE in C. diffcile pathogenesis by employing the well standardized C. difficile hamster infection model. Since TcdE has a prominent role in toxin secretion, this study can help us to understand the toxin secretion mechanism and its significance in C. difficile pathogenesis.
Severity and the incidence of Clostridium difficile-associated disease are on the rise, making C. difficile infections as one of the major public health concern in the United States. The research proposed here has relevance to public health, because it focuses on understanding the mechanisms involved in the production of TcdE, a protein needed for toxins secretion in C. difficile.
