Antimicrobial efficacy of 405nm light against Clostridium difficile: evidence of enhanced sporicidal activity when combined with disinfectants

Clostridium difficile can cause major contamination problems due to its ability to form highly infectious and resilient spores which can survive in the environment for prolonged periods. Recent work has demonstrated the use of antimicrobial 405nm light for environmental decontamination within hospitals, however further information relating to efficacy against spores is required.
The aim of this investigation was to establish the efficacy of 405nm light for inactivation of C. difficile vegetative cells and spores, and to establish whether spore susceptibility can be enhanced by the combined use of 405nm light with low concentration chlorinated and non-chlorinated disinfectants.
C. difficile vegetative cells and spore suspensions were exposed to increasing doses of 405nm light (70-225mW/cm2) to establish sensitivity. Exposures were repeated with spores suspended in a range of routine hospital disinfectants at varying concentrations.
A 99.9% reduction in vegetative cell population was demonstrated with a dose of 252J/cm2, however spores demonstrated higher resilience, with a 10-fold increase in dose required. Enhanced sporicidal activity was achieved when spores were exposed in the presence of low concentration disinfectant
s, with 50% increase in susceptibility when exposed in the presence of 0.1% sodium hypochlorite.
C. difficile vegetative cells and spores can be successfully inactivated using 405nm light, and the sporicidal efficacy can be significantly enhanc
ed when exposed in the presence of low concentrations of disinfectants. Further research may lead to potential use of 405nm light decontamination in combination with hospital disinfectants to enhance C. difficile cleaning and
infection control procedures.