Clostridium difficile strain 630DErm is a derivative of the clinical isolate 630 [34, 35] , a PCR ribotype 012 strain. PCR ribotypes 012 strains constitute 4% of the clinically isolated toxinogenic isolates in Europe [7] . Clostridium difficile 630 (PCR ribotype 012)-derived strains are commonly used to investigate virulence of mutants [26, 36, 37] .