Ultraviolet C light with wavelength of 222 nm inactivates a wide spectrum of microbial pathogens

Background: Ultraviolet C (UVC) light has been used to inactivate several pathogens. Unlike conventional 254-nm UVC, 222-nm UVC is harmless to mammalian cells. Aim: To investigate the disinfection efficacy of 222-nm UVC against human pathogens which are commonly found in the environment and healthcare facilities. Methodology: Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Salmonella enterica subsp. serovar Typhimurium, Campylobacter jejuni, Bacillus cereus (vegetative cells and endospores), Clostridium sporogenes (vegetative cells and endospores), Clostoridioides difficile (endospores), Candida albicans (yeast), Aspergillus niger (hyphae and spores), Trichophyton rubrum (hyphae and spores), feline calicivirus and influenza A virus were irradiated with 222-nm UVC at various doses. The remaining live bacterial and fungal cells, and viral infectivity were evaluated. The germicidal effect of 222-nm UVC was compared with that of 254-nm UVC. Results: UVC with a wavelength of 222 nm had a potent germicidal effect on vegetative bacterial cells, yeast and viruses, and was as efficient as 245-nm UVC. In addition, 222-nm UVC had a more potent germicidal effect on bacterial endospores compared with 254-nm UVC. The fungicidal effect of 222-nm UVC against fungal spores and hyphae was weaker than that of 254-nm UVC. Conclusions: UVC with a wavelength of 222 nm was able to inactivate a wide spectrum of microbial pathogens. In comparison with 254-nm UVC, the germicidal effect of 222-nm UVC for fungal hyphae and spores was low, but 222-nm UVC had a strong germicidal effect on bacterial endospores.(C) 2020 The Authors. Published by Elsevier Ltd on behalf of The Healthcare Infection Society. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).