222-nm UVC inactivates a wide spectrum of microbial pathogens.

Background: UVC has been used to inactivate several pathogens. Unlike the 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 the viral infectivity were evaluated. The efficiency of 222-nm UVC germicidal effect was compared to that of the conventional 254-nm UVC.

Results: The 222-nm UVC showed potent germicidal effect to vegetative bacterial cells, yeast and viruses as efficient as the 245-nm UVC. The 222-nm UVC exhibited more potent germicidal effect to bacterial endospores, compared with the 254-nm UVC. The fungicidal effect of 222-nm UVC against the fungal spores and hyphae was weaker than that of 254-nm UVC.

Conclusions: The 222-nm UVC is able to inactivate a wide spectrum of microbial pathogens. In comparison with the conventional 254-nm UVC, the germicidal effect of 222-nm UVC to the fungal hyphae and spores is low, but the 222-nm UVC exhibits strong germicidal effect to the bacterial endospores.