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Development of a high-level light-activated disinfectant for hard surfaces and medical devices
Matthew P Wylie1, Rebecca A Craig1, Sean P Gorman1
1School of Pharmacy, Queen's University Belfast, Belfast, UK.
Background:
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.
Methods:
Susceptibility of Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa and Escherichia coli to phenothiazinium photosensitizers and cationic surfactants under white- or red-light irradiation was assessed by determination of minimum inhibitory concentrations, minimum bactericidal concentrations and time-kill assays. B. subtilis spore eradication was assessed via time-kill assays, with and without nutrient and non-nutrient germinant supplementation of photosensitizer, surfactant and photosensitizer-surfactant solutions in the presence and absence of light.
Results:
Under red-light irradiation, >5-log10 colony-forming units/mL reduction of vegetative bacteria was achieved within 10 min with toluidine blue O (TBO) and methylene blue (MB). Cationic surfactant addition did not significantly enhance spore eradication by photosensitizers (P>0.05). However, addition of a nutrient germinant mixture to TBO achieved a 6-log10 reduction after 20 min of irradiation, while providing 1-2 log10 improvement in spore eradication for MB and pyronin Y.
Conclusions:
Light-activated photosensitizer 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 health care.
Insights
Phenothiazinium photosensitizers with germination agents effectively eradicate dormant and vegetative bacteria. This light-activated approach offers a promising alternative for healthcare decontamination and infection control.
Area of Science:
- Microbiology
- Photochemistry
- Infection Control
Background:
- Bacterial spores pose a significant challenge in healthcare settings due to persistent contamination and transmission risks.
- Current sporicides are often toxic and costly, limiting their widespread use for effective decontamination.
Purpose of the Study:
- To evaluate the efficacy of phenothiazinium photosensitizers and cationic surfactants against vegetative bacteria and bacterial spores.
- To assess the impact of light irradiation and germinant supplementation on the antimicrobial activity of these agents.
Main Methods:
- Minimum inhibitory concentrations, minimum bactericidal concentrations, and time-kill assays were performed on Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, and Escherichia coli.
- Bacterial spore eradication was specifically assessed using time-kill assays with and without nutrient germinants and light exposure.
Main Results:
- Red-light irradiation with toluidine blue O (TBO) and methylene blue (MB) achieved >5-log10 reduction of vegetative bacteria within 10 minutes.
- Cationic surfactants did not significantly enhance photosensitizer-mediated spore eradication.
- TBO with nutrient germinants achieved a 6-log10 spore reduction in 20 minutes, with MB and pyronin Y showing 1-2 log10 improvement.
Conclusions:
- Light-activated photosensitizer solutions, enhanced by surfactants and germination agents, effectively eradicate both dormant bacterial spores and vegetative bacteria.
- This method presents a viable alternative to conventional chemical agents for high-level decontamination in healthcare environments.
- The findings support the development of novel photodynamic strategies for infection control and prevention of cross-contamination.
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