Investigation of 222-nm ultraviolet C irradiation bactericidal effect on the surgical field in a rabbit model.

Ultraviolet C (UV-C) not only has a bactericidal effect, but is also cytotoxic; however, UV-C at a wavelength of 222 nm with a high absorption coefficient for proteins is considered safe. We have previously reported the safety of 222-nm UV-C irradiation in humans and rabbits. This study evaluated the bactericidal effect of 222-nm UV-C irradiation on exposed surgical fields. Sixteen-week-old female rabbits were used, and the exposed area on their backs was sprayed with a bacterial solution from swabs collected from their soles. Three groups were formed based on UV-C irradiation: 500 mJ/cm² of 222-nm UV-C, 200 mJ/cm² of 254-nm UV-C, which is commonly used in germicidal lamps, and non-UV-C irradiation. The bacterial colonies were counted after irradiation. Both UV-C groups showed a significant reduction in bacterial colonies compared to the nonirradiated group, with no significant difference between the two UV-C groups. Microbiota analysis identified species that could cause surgical site infections. The results of the study suggest that 500 mJ/cm² of 222-nm UV-C irradiation effectively reduces bacterial load, with a bactericidal effect comparable to 254-nm UV-C; hence, 222-nm UV-C irradiation is a promising and safe tool for minimizing the risk of surgical site infections.