A Pilot Study to Investigate the Antimicrobial Activity of Pulsed UVA and UVC

Abstract

UV irradiation has shown potential in reducing bacterial and viral loadings. This is a pilot study aimed at investigating the antimicrobial effect of a novel pulsed UVA and UVC technology on bacteria and human coronavirus 229E. The selection of these microorganisms is based on their relevance and significance in real-world scenarios. This study consists of independent experiments for the assessment of antibacterial and antiviral activities by using a lawn plate approach, measuring levels of adenine triphosphate (ATP) in three bacterial strains, Escherichia coli, Staphylococcus epidermidis and Bacillus subtilis, and performing Median Tissue Culture Infectious Dose (TCID50) of HCoV-229E on MRC-5 human lung fibroblast cell line. The results demonstrated the ability of UVA and UVC irradiation to reduce levels of adenine triphosphate (ATP) over a 12 h exposure period in all three bacterial strains, comparative to dark and artificial/natural light conditions using non-pulsing experiments. In addition to this, there was a reduction in colonies exposed to UVA and UVC pulsing experiments for E. coli K12 and S. epidermis compared to bacteria stored in artificial/natural and dark conditions. Furthermore, using dose-dependent modelling, it was demonstrated that the cross-contamination risk was reduced by 50% using E. coli as a typical model. Regarding the antiviral assay, the results showed that TCID50 of HCoV-229E was reduced after the first cycle of UV engagement. No cytopathic effect (CPE) was detected after three cycles using Protocol 1. The findings showed that UVA and UVC were effective under the conditions outlined in this paper for a reduction in the number of bacteria with additional applications to viruses.