Efficiency of Controlled UVC Dose Emission by Mercury Lamps and LED Array Against Clinically Relevant Pathogenic Bacteria

AIM: Ultraviolet C radiation (UVC; λ = 100-280 nm) is a well-established physical agent for microbial inactivation, widely applied in surface and environmental disinfection. Considering the increasing demand for efficient, safe, and automated disinfection systems, this study compares the performance of two low-pressure mercury lamps with different wattages and a novel UVC-LED array in terms of UVC irradiance, DNA damage induction, and microbiological inactivation. METHODS: DNA photodamage was assessed in vitro via cyclobutane pyrimidine dimer (CPD) detection, and bacteriological inactivation was evaluated with four relevant pathogenic bacteria (Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae carbapenemase (KPC), and Pseudomonas aeruginosa) exposed to increasing UVC doses (0-50 J/m²). RESULTS: All UVC sources induced a dose-dependent increase of DNA lesions and microbial inactivation, with 50 J/m² achieving an average inactivation rate of 99.98%. Although higher-power mercury lamps delivered higher dose rates (J/m²/s), the UVC-LED device showed comparable germicidal efficacy, with advantages in energy efficiency, operational lifespan and environmental safety. CONCLUSIONS: The results presented in this work indicate the feasibility of complementing the use of mercury-based lamps with UVC-LEDs due to its great potential application for point-of-use disinfection approaches. Furthermore, the obtained results also highlight the importance of controlled digital dosimetry to improve the UVC-based technologies application for disinfection of bacteria of hospital concern.