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Photoinactivation by UVA radiation and visible light of Candida auris compared to other fungi
Anna-Maria Gierke1, Martin Hessling2
1Institute of Medical Engineering and Mechatronics, Ulm University of Applied Sciences, Albert-Einstein-Allee 55, 89081, Ulm, Germany. anna-maria.gierke@thu.de.
Abstract:
In addition to the rising number of patients affected by viruses and bacteria, the number of fungal infections has also been rising over the years. Due to the increase in resistance to various antimycotics, investigations into further disinfection options are important. In this study, two yeasts (Candida auris and Saccharomyces cerevisiae) and a mold (Cladosporium cladosporioides) were irradiated at 365, 400, and 450 nm individually. The resulting log 1 reduction doses were determined and compared with other studies. Furthermore, fluorescence measurements of C. auris were performed to detect possible involved photosensitizers. A roughly exponential photoinactivation was observed for all three fungi and all irradiation wavelengths with higher D90 doses for longer wavelengths. The determined log 1 reduction doses of C. auris and S. cerevisiae converged with increasing wavelength. However, S. cerevisiae was more photosensitive than C. auris for all irradiation wavelengths and is therefore not a suitable C. auris surrogate for photoinactivation experiments. For the mold C. cladosporioides, much higher D90 doses were determined than for both yeasts. Concerning potential photosensitizers, flavins and various porphyrins were detected by fluorescence measurements. By excitation at 365 nm, another, so far unreported fluorophore and potential photosensitizer was also observed. Based on its fluorescence spectrum, we assume it to be thiamine.Graphic abstract.
Insights
Rising fungal infections necessitate new disinfection methods. This study shows light inactivation of fungi varies by species and wavelength, with flavins, porphyrins, and potentially thiamine acting as photosensitizers.
Area of Science:
- Microbiology
- Photobiology
- Antimicrobial Research
Background:
- Increasing prevalence of fungal infections.
- Growing resistance to conventional antimycotic treatments.
- Need for alternative disinfection strategies.
Purpose of the Study:
- Investigate photoinactivation of pathogenic fungi using specific light wavelengths.
- Determine the efficacy of light disinfection against Candida auris, Saccharomyces cerevisiae, and Cladosporium cladosporioides.
- Identify potential photosensitizers involved in fungal photoinactivation.
Main Methods:
- Irradiation of fungal species (Candida auris, Saccharomyces cerevisiae, Cladosporium cladosporioides) at 365, 400, and 450 nm.
- Determination of log10 reduction doses (D90) for each fungus and wavelength.
- Fluorescence spectroscopy of Candida auris to detect photosensitizing compounds.
Main Results:
- Photoinactivation observed for all fungi and wavelengths, with higher doses required for longer wavelengths.
- Saccharomyces cerevisiae showed higher photosensitivity than Candida auris, indicating it's not a suitable surrogate.
- Cladosporium cladosporioides required significantly higher D90 doses compared to both yeasts.
- Fluorescence measurements detected flavins, porphyrins, and a potential thiamine-based photosensitizer.
Conclusions:
- Light irradiation is a viable disinfection method for fungi, with efficacy dependent on wavelength and fungal species.
- Candida auris and Saccharomyces cerevisiae exhibit differential photosensitivity, impacting experimental design.
- Identification of potential photosensitizers like thiamine opens avenues for enhancing light-based antifungal strategies.
