Synergistic efficacy of 405 nm light and chlorinated disinfectants for the enhanced decontamination of Clostridium difficile spores

Abstract

The ability of Clostridium difficile to form highly resilient spores which can survive in the environment for prolonged periods causes major contamination problems. Antimicrobial 405nm light is being developed for environmental decontamination within hospitals, however further information relating to its sporicidal efficacy is required. This study aims 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 disinfectants. Vegetative cells and spore suspensions were exposed to increasing doses of 405nm light (at 70-225 mW/cm 2 ) to establish sensitivity. A 99.9% reduction in vegetative cell population was demonstrated with a dose of 252 J/cm 2 , however spores demonstrated higher resilience, with a 10-fold increase in required dose. Exposures were repeated with spores suspended in the hospital disinfectants sodium hypochlorite, Actichlor and Tristel at non-lethal concentrations (0.1%, 0.001% and 0.0001%, respectively). Enhanced sporicidal activity was achieved when spores were exposed to 405nm light in the presence of the disinfectants, with a 99.9% reduction achieved following exposure to 33% less light dose than required when exposed to 405nm light alone. In conclusion, C. difficile vegetative cells and spores can be successfully inactivated using 405nm light, the sporicidal efficacy can be significantly enhanced when exposed in the presence of low concentration chlorinated disinfectants. Further research may lead to the potential use of 405nm light decontamination in combination with selected hospital disinfectants to enhance C. difficile cleaning and infection control procedures.

Characterizing the Antimicrobial Properties of 405 nm Light and the Corning® Light‐Diffusing Fiber Delivery System

“…Yet, this appeared to be an organism-specific phenomenon, as another Gram-negative pathogen, P. aeruginosa, displayed the greatest susceptibility as measured by reduction in cell viability of the bacterial species tested. Similarly, S. aureus exhibited appreciable 405 nm decolonization properties suggesting that the technology may be applicable to decolonizing hospital associated surfaces and warrant future studies aimed at comprehensively understanding the spectrum of susceptible species, dosing powers, and the recently recognized synergistic potential of 405 nm light in combination with chemical disinfectants [39]. We also measured the LDF system's performance toward planktonic bacteria.…”

Antimicrobial blue light inactivation of pathogenic microbes: State of the art

“…Moorhead et al established the efficacy of the combination therapy of aBL with low concentration chlorinated disinfectants for enhanced inactivation of C. difficile spores (Moorhead et al, 2016a). C. difficile spores suspended in the hospital disinfectants sodium hypochlorite, Actichlor or Tristel at non-lethal concentrations were exposed to aBL at 405 nm.…”

Review of the Comparative Susceptibility of Microbial Species to Photoinactivation Using 380–480 nm Violet‐Blue Light

“…For example, Haughton et al (2012) inactivated Campylobacter jejuni using 395 nm light, while Bumah et al (14,15) demonstrated the antimicrobial efficacy of 470 nm light against Salmonella enterica and S. aureus. Additionally, a small number of bacterial endospores, fungi and yeasts have been inactivated using violet-blue light (16)(17)(18)(19)(20)(21)(22)(23). To date, little is known about viral susceptibility; however, there is now published evidence demonstrating 405 nm light inactivation of a viral surrogate, bacteriophage ɸC31, and a mammalian virus, feline calicivirus, without the requirement of additional photosensitizers (24,25).…”