Syngergistic efficacy of 405 nm light and hospital disinfectants for the enhanced decontamination of C. difficile on clinically relevant surfaces

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The ability of Clostridium difficile to form highly infectious and resilient spores which can survive in the environment for prolonged periods causes major contamination problems.
Antimicrobial 405 nm light is capable of inactivating a wide range of organisms, including endospore-forming bacteria, and is being developed for environmental decontamination within hospitals, however further information relating to its efficacy against spores is required. This study aims to establish the efficacy of 405 nm light for inactivation of C. difficile vegetative cells and spores, and to establish whether spore susceptibility can be enhanced by the combined use of 405 nm light with low concentration chlorinated and non-chlorinated disinfectants, in both liquid suspension and on surfaces.
C. difficile vegetative cells and spore suspensions were exposed to increasing doses of 405 nm light (using irradiances of 70-225 mW/cm2) to establish sensitivity. Exposures were repeated with spores suspended in a range of routine hospital disinfectants at varying concentrations. Controls were exposed to 405 nm light in the absence of disinfectants, and disinfectants in the absence of 405 nm light, to establish the sporicidal activity of each agent alone, and to demonstrate the synergistic effect when combined. These experiments were repeated with spores seeded onto a range of relevant inert surfaces.
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 to 405 nm light in the presence of low concentration disinfectants, with a 50% increase in susceptibility when exposed in the presence of 0.1% sodium hypochlorite. Synergy was also noted with the other disinfectants used.
In conclusion, C. difficile vegetative cells and spores can be successfully inactivated using 405nm light, and the sporicidal efficacy can be significantly enhanced when exposed in the presence of low concentrations of disinfectants. Further research may lead to potential use of 405nm light decontamination in combination with selected hospital disinfectants to enhance C. difficile cleaning and infection control procedures.
Original languageEnglish
Number of pages1
Publication statusPublished - 21 May 2015
Event5th International Clostridium difficile symposium - Lake Bled, Slovenia
Duration: 19 May 201521 Jan 2016


Conference5th International Clostridium difficile symposium
CityLake Bled


  • Clostridium difficile
  • spores
  • decontamination
  • 405nm light
  • disinfectants

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