C. difficile is a Gram positive, anaerobic bacterium that is the causative agent of C. difficile infection (CDI) (for recent reviews see [24, 25] ). Though many people are asymptomatically colonized by C. difficile, the bacterium can cause serious health problems, such as pseudomembranous colitis and toxic megacolon, under the influence of risk factors such as age and antibiotic use. As a result, CDI was long regarded a nosocomial infection. Recently, however, an increase in the cases of community acquired CDI can be observed [26] . Outbreaks of CDI have been linked to so called hypervirulent strains, such as PCR ribotypes 027 (BI/ NAP1) and 078 [27, 28] . Its main virulence factors are the major clostridial toxins A and B [29, 30] . In addition, certain strains of C. difficile, including ribotypes 027 and 078, additionally encode a binary toxin [31, 32] . C. difficile is transmitted via the fecal-oral route. It is believed that spores are crucial to successfully infect new hosts, as they are able to withstand the harsh environment of the stomach, and survive antibiotic treatments that alter the endogenous flora, after which C. difficile can overgrow [24, 25] .