ReviewExtrachromosomal and integrated genetic elements in Clostridium difficile

- Clostridium difficile causes gastrointestinal disease in antibiotic-treated patients.
- Clostridium difficile contains many extrachromosomal and integrated genetic elements.
- Recent genomic work has given new insights into the variability and distribution of Clostridium difficile elements.
- Thirty years of research and the function of mobile genetic elements in Clostridium difficile phenotypes is discussed.
- We review Clostridium difficile antibiotic resistance determinants associated with mobile genetic elements.

Clostridium difficile is a major nosocomial pathogen, causing gastrointestinal disease in patients undergoing antibiotic therapy. This bacterium contains many extrachromosomal and integrated genetic elements, with recent genomic work giving new insights into their variability and distribution. This review summarises research conducted in this area over the last 30 years and includes a discussion on the functional contributions of these elements to host cell phenotypes, as well as encompassing recent genome sequencing studies that have contributed to our understanding of their evolution and dissemination. Importantly, we also include a review of antibiotic resistance determinants associated with mobile genetic elements since antibiotic use and the spread of antibiotic resistance are currently of significant global clinical importance.