Photoinactivation of <i>Staphylococcus carnosus</i> on Surfaces by Irradiation with Blue and Violet Light

Abstract

To control the spread of bacteria and viruses on surfaces in medical environments and everyday life, suitable disinfection methods are required. Visible radiation in the violet or blue spectral range is known to exhibit an antimicrobial impact on microorganisms. However, so far most published studies were performed on liquids. In contrast, the sensitivity of microorganisms to visible radiation on surfaces was only investigated in a few studies. In order to transfer possible conclusions from irradiation in media to irradiation on surfaces and to apply visible light as a possible valid alternative for common disinfection methods, the log reduction doses for surfaces and liquids were compared in this study. The non-pathogenic Staphylococcus carnosus was selected as a surrogate for the ESKAPE pathogen Staphylococcus aureus, as the experiments were performed in an S1 laboratory. The irradiations were performed with wavelengths of 403 nm (violet) and 453 nm (blue). The observed log reduction doses in liquids (literature with the same strain and setup) and on surfaces (this investigation) were 101.8 J/cm2 and 14.0 J/cm2 at 403 nm and 374.3 J/cm2 and 112.8 J/cm2 at 453 nm, respectively. The results suggest that the photosensitivity of S. carnosus on surfaces is much higher than in that liquid with a ratio of 7.3 (violet) to 3.3 (blue). On the one hand, this demonstrates that irradiation on surfaces is more efficient than that in liquids, especially in the violet spectral range. On the other hand, depending on the strength of the irradiation source, disinfection with visible irradiation is a useful alternative to conventional disinfection methods.

Keywords

• visible irradiation
• blue light
• violet light
• surface
• bacteria
• <i>Staphylococcus carnosus</i>