Yeasticidal efficacy of far-UV-C radiation with 233 nm peak wavelength for inactivating Candida spp. with focus on the clinically relevant species C. auris for potential application on the skin.

Background: Candida spp. are significant pathogens for hospital-acquired infections. Infections with Candida auris especially have gained increased attention due to their transmissibility and resistance properties, making new decolonization tools necessary. Far-ultraviolet-C (UV-C) radiation might be a new tool to inactivate Candida spp. independent of their resistance profile. The use of light-emitting diodes (LEDs) allows a flexible application of the radiation enabling, for example, the treatment of areas that are not accessible by the use of common antiseptics such as the throat or the middle ear.

Aim: To evaluate the inactivation efficacy of 233 nm radiation against Candida spp. using a quantitative carrier test for proof of principle based on EN 14562, EN17272, and ASTM E2197.

Methods: A blood agar spot test and a carrier test were used to quantify the efficacy of Candida spp. inactivation by skin-tolerable doses of UV-C radiation (10-60 mJ/cm) with a peak wavelength of 233 nm. C. albicans, C. parapsilosis, C. glabrata, C. tropicalis and C. auris were used for the tests. C. parapsilosis was furthermore incubated with l-DOPA for melanin externalization.

Findings: A dose of 60 mJ/cm was able to inactivate >3 log of all Candida spp.; in some experiments, a 4 log reduction was achieved. C. parapsilosis with melanin and C. auris DSM 105987 were the least susceptible strains.

Conclusion: Far-UV-C radiation might be an additional measure for the treatment of candida infections due to its yeasticidal effects combined with its skin tolerability.