Development of Clostridium difficile R20291ΔPaLoc model strains and in vitro methodologies reveals CdtR is required for the production of CDT to cytotoxic levels

- Model strains to study the C. difficile binary toxin, CDT, were generated by deleting the PaLoc in R20291.
- The gene encoding CdtR was deleted and re-integrated on the chromosome in the model strains.
- In vitro Cytotoxicity assays were established to assess CDT-mediated virulence.
- CdtR was required for the production of CDT to cytotoxic levels towards Vero cells.

Assessing the regulation of Clostridium difficile transferase (CDT), is complicated by the presence of a Pathogenicity locus (PaLoc) which encodes Toxins A and B. Here we developed R20291ΔPaLoc model strains and cell-based assays to quantify CDT-mediated virulence. Their application demonstrated that the transcriptional regulator, CdtR, was required for CDT-mediated cytotoxicity.