Antimicrobial efficacy and inactivation kinetics of a novel LED-based UV-irradiation technology

Ultraviolet (UV)-light-emitting diodes (UV-LEDs) are energy efficient and of special interest for the inactivation of micro-organisms. In the context of the coronavirus disease 2019 pandemic, novel UV technologies can offer a powerful alternative for effective infection prevention and control.

This study assessed the antimicrobial efficacy of UV-C LEDs on Escherichia coli, Pseudomonas fluorescens and Listeria innocua, as well as severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), human immunodeficiency virus-1 (HIV-1) and murine norovirus (MNV), dried on inanimate surfaces, based on European Standard EN 17272.

This study found 90% inactivation rates for the tested bacteria at mean UV-C doses, averaged over all three investigated UV-C wavelengths, of 1.7 mJ/cm² for E. coli, 1.9 mJ/cm² for P. fluorescens and 1.5 mJ/cm² for L. innocua. For the tested viruses, UV doses <15 mJ/cm² resulted in 90% inactivation at wavelengths of 255 and 265 nm. Exposure of viruses to longer UV wavelengths, such as 275 and 285 nm, required much higher doses (up to 120 mJ/cm²) for inactivation. Regarding inactivation, non-enveloped MNV required much higher UV doses for all tested wavelengths compared with SARS-CoV-2 or HIV-1.

Overall, the results support the use of LEDs emitting at shorter wavelengths of the UV-C spectrum to inactivate bacteria as well as enveloped and non-enveloped viruses by exposure to the appropriate UV dose. However, low availability and excessive production costs of shortwave UV-C LEDs restricts implementation at present, and supports the use of longwave UV-C LEDs in combination with higher irradiation doses.