Disinfection and healing effects of 222-nm UVC light on methicillin-resistant Staphylococcus aureus infection in mouse wounds

Abstract

UVC radiation is known to be highly germicidal. However, exposure to 254-nm-UVC light causes DNA lesions such as cyclobutane pyrimidine dimers (CPD) in human cells, and can induce skin cancer after long-term repeated exposures. It has been reported that short wavelength UVC is absorbed by proteins in the membrane and cytosol, and fails to reach the nucleus of human cells. Hence, irradiation with 222-nm UVC might be an optimum combination of effective disinfection and biological safety to human cells. In this study, the biological effectiveness of 222-nm UVC was investigated using a mouse model of a skin wound infected with methicillin-resistant Staphylococcus aureus (MRSA). Irradiation with 222-nm UVC significantly reduced bacterial numbers on the skin surface compared with non-irradiated skin. Bacterial counts in wounds evaluated on days 3, 5, 8 and 12 after irradiation demonstrated that the bactericidal effect of 222-nm UVC was equal to or more effective than 254-nm UVC. Histological analysis revealed that migration of keratinocytes which is essential for the wound healing process was impaired in wounds irradiated with 254-nm UVC, but was unaffected in 222-nm UVC irradiated wounds. No CPD-expressing cells were detected in either epidermis or dermis of wounds irradiated with 222-nm UVC, whereas CPD-expressing cells were found in both epidermis and dermis irradiation with 254-nm UVC. These results suggest that 222-nm UVC light may be a safe and effective way to reduce the rate of surgical site and other wound infections.

Far-UVC light efficiently and safely inactivates airborne human coronaviruses

“…The severity of the 2020 COVID-19 pandemic warrants the rapid development and deployment of effective countermeasures to reduce person-to-person transmission. We have developed a promising approach using single-wavelength far-UVC light at 222 nm generated by filtered excimer lamps, which inactivate viruses and bacteria, without inducing biological damage in exposed human cells and tissue [11][12][13][14][15][16]. The approach is based on the biophysically-based principle that far-UVC light, because of its very limited penetration in biological materials, can traverse and kill viruses and bacteria which are typically micrometer dimensions or smaller, but it cannot penetrate even the outer dead-cell layers of human skin, nor the outer tear layer on the surface of the human eye 12 .…”

“…Thus far-UVC light has about the same highly effective germicidal properties of UV light, but without the associated human health risks [12][13][14][15] . Several groups have thus proposed that far-UVC light (207 or 222 nm), which can be generated using inexpensive excimer lamps, is a potential safe and efficient anti-microbial technology [12][13][14][15][16][17][18] which can be deployed in occupied public locations.…”

Evaluation of the sterilization effect of a new mercury-free UVC light source

“…C. albicans (ATCC10231), S. aureus (ATCC25923), P. aeruginosa (ATCC9027), and E. coli (ATCC25922) obtained from American Type Culture Collection, were cultured at 37°C in tryptic soy broth (pH 7.2, BD Diagnosis Systems, Sparks, MD) [13][14][15] . All the bacteria and yeast kept on a rotary shaker at 220 rpm were cultivated for 8 h. The concentration of cells was 10 9 CFU/ml as assessed by 600 nm absorption.…”

Can light‐based approaches overcome antimicrobial resistance?

“…(c) S. aureus CFU extracted from a mouse wound either immediately or 24 hr after treatment with 750 mJ/cm 2 of either 222 nm or 254 nm UVC. (d) Percentage (%) of CPD‐positive cells quantified by counting 10 random high‐power (×400) fields of tissue sections removed 1 hr postexposure to 150 mJ/cm 2 of either 222 nm or 254 nm UVCFrom Narita et al () no permission necessary…”