Development of a high-level light-activated disinfectant for hard surfaces and medical devices

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Bacterial spores are an important consideration in healthcare decontamination, with cross-contamination highlighted as a major route of transmission due to their persistent nature. Their containment is extremely difficult due to the toxicity and cost of first-line sporicides. Susceptibility of Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa and Escherichia coli to phenothiazinium photosensitisers and cationic surfactants under white- or red-light irradiation was assessed by determination of MICs, MBCs and time-kill assays. B. subtilis spore eradication was assessed via time-kill assays, with and without nutrient and non-nutrient germinant supplementation of photosensitiser, surfactant and photosensitiser-surfactant solutions in the presence and absence of light. Under red light irradiation, >5-log cfu/mL reduction of vegetative bacteria was achieved within 10 minutes with Toluidine Blue O (TBO) and methylene blue (MB). Cationic surfactant addition did not significantly enhance spore eradication by photosensitisers (p>0.05). However, addition of a nutrient germinant mixture to TBO achieved 6-log reductions after 20 minutes irradiation, while providing 1-2 log improvements in spore eradication for MB and Pyronin Y. Light-activated photosensitiser solutions in the presence of surfactants and germination-promoting agents provide a highly effective method to eradicate dormant and vegetative bacteria. These solutions could provide a useful alternative to traditional chemical agents used for high-level decontamination and infection control within healthcare. 
Original languageEnglish
Article number106360
JournalInternational journal of antimicrobial agents
Early online date13 May 2021
Publication statusEarly online date - 13 May 2021


  • Bacillus
  • Bacterial spores
  • Cationic surfactants
  • Germinants
  • Photodynamic therapy
  • Photosensitisers


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