Photoinactivation of Staphylococcus carnosus on surfaces by irradiation with blue and violet light

To control the growth bacteria and viruses in medical environments and everyday life on surfaces, suitable disinfection methods are required. The visible radiation in the violet or blue spectral range is known to have a disinfecting effect on microorganisms; however, so far most published studies were performed in liquids. In contrast, the sensitivity of microorganisms to visible radiation on surfaces were only investigated in a few studies.
In order to transfer possible conclusions from irradiation in media to irradiation on surfaces and to apply irradiation in the visible spectral range as a possible valid alternative for common disinfection methods, the log reduction for surfaces and liquids were compared in this study. The non-pathogenic Staphylococcus carnosus was selected as surrogate for the ESKAPE pathogen Staphylococcus aureus, as the experiments were performed in a S1 laboratory. The irradiations were performed with wavelengths of 403 nm (violet) and 453 nm (blue).
The observed log reduction doses in liquids and surfaces were 96.2 J/cm² and 15.8 J/cm² at 403 nm and 175.4 J/cm² and 112.4 J/cm² at 453 nm, respectively. The results suggest that the photosensitivity of S. carnosus on surfaces is much higher than in liquid with a ratio of 6.1 (violet) and 1.6 (blue).
On the one hand, this demonstrates that irradiation on surfaces is more efficient than 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.