Our work and that of Cartman and coworkers [38] seem at odds with the previous reports that clearly demonstrate that TcdC can act as a repressor for toxin gene expression [12, 30] . However, we cannot exclude the possibility that TcdC exerts a more profound effect under specific conditions, or in other strains of C. difficile than 630Derm and R20291. It should be clear though that in vivo relevance of TcdC for toxin regulation in these two strains is limited.