Single-Wavelength UV Light Reduces Surgical Site Infections

A new study suggests that ultraviolet (UV) light in the far-UVC 207 nm wavelength kills bacteria without apparent harm to human skin tissue.

Researchers at Columbia University Medical Center (CUMC; New York, NY, USA) conducted a study in hairless mice to test the hypothesis that 207 nm UVC light is not cytotoxic to exposed mammalian skin. The mice were exposed to a fluence of 157 mJ/cm2 of UVC, delivered by a krypton-bromine (Kr-Br) excimer lamp that produces high-intensity light at 207 nm. Similar mice were exposed to a conventional 254-nm UV germicidal lamp. Study controls involved mice unexposed to UVC light.

The researchers characterized eight relevant cellular and molecular damage endpoints, including epidermal hyperplasia, pre-mutagenic DNA lesions, skin inflammation, and normal cell proliferation and differentiation. The results showed that while conventional 254 nm germicidal UV exposure produced significant effects for all the studied skin damage endpoints, the same fluence delivered by 207 nm UVC light produced results that were not statistically distinguishable from zero exposure controls. The study was published on June 8, 2016, in PLOS One.

“The mechanistic background is that far UVC light in the wavelength range of around 200 to 220 nm is strongly absorbed by essentially all proteins, and so its ability to penetrate biological material is very limited,” concluded lead author Manuela Buonanno, PhD, of the CUMC Center for Radiological Research (CRR). “The very short half value distance of 207 nm UV light in biological material means that, while it can penetrate bacteria and viruses that are typically smaller than 1 μm in size, it cannot penetrate the human stratum corneum, nor the ocular cornea, nor the cytoplasm of individual human cells.”

“We’ve known for a long time that UV light has the potential to reduce surgical site infections, because UV can efficiently kill all bacteria, including drug-resistant bacteria and even so-called superbugs,” added senior author Professor David Brenner, PhD, director of the CRR. “Unfortunately, it’s not possible to use conventional germicidal UV light when people are around, because it’s a health hazard to patients and medical personnel. With this new research, we have demonstrated that far-UVC kills bacteria, but without risk of skin damage.”

SSIs is most frequent healthcare-associated infection (HAI) after asymptomatic bacteriuria, representing a high burden on patients and hospitals in terms of morbidity, mortality, prolonged length of hospital stay, and additional costs. Each year, approximately 500,000 surgical patients develop SSIs.

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