The greater efficacy obtained by other authors may be explained not only by the method used or by their not having used micro-organisms recently isolated from patients, but also by the use of more concentrated peroxide (one example: 30%; our study: 5%).5 and 7 We have not studied other micro-organisms such as Clostridium difficile, because vegetative forms are highly susceptible and their sporulation needs several days on the carrier, producing different kill rates compared with other inoculated micro-organisms (left to dry for 60 min). Moreover, the susceptibility of C. difficile in dirty conditions was similar to, or less than, other included bacteria such as S. aureus or acinetobacter, according to Fu et al.