UV-C light-based surface disinfection: Analysis of its virucidal efficacy using a bacteriophage model

ABSTRACT

Introduction Reprocessing of medical devices becomes increasingly complex, due to higher hygiene requirements. Former studies revealed satisfactory bactericidal properties of UV-C light disinfection in otorhinolaryngological endoscopes. Especially in the context of the current COVID-19 pandemic, virucidal properties are of high importance. In this study the virucidal efficacy of UV-C light disinfection was analyzed using a bacteriophage model. Materials and methods MS-2 bacteriophages were used as surrogate for stable viruses with high tenacity. The bacteriophage samples were irradiated for up to three cycles of 25 seconds by UV-C light (D25, UV-Smart Technologies B.V.). A dilution series of the irradiated test samples was mixed with 1x108 CFU of Escherichia coli. After incubation plaque formation of Escherichia coli were counted and hence the phage concentration was determined. Results The initial contamination of the test samples was 1.8x1012 plaque forming units (pfu). After 25 seconds of UV-C light irradiation, a non-significant Log reduction of 2.2 was found (p = 0,82). After 50 and 75 seconds of UV-exposure a significant Log reduction of 3.4 e.g. 5.1 (p = 0.05 e.g. p = 0.004) was found. The control sample showed a titer of 1.2 x 1010 pfu. Conclusion The tested UV system seems to provide a significant virucidal effect after a short time of exposure. In combination with the results of the bacteriological testing it appears suitable for clinical use as a substitute for current disinfection methods.