Efficacy of violet–blue light to inactive microbial growth

The increase in health care-associated infections and antibiotic resistance has led to a growing interest in the search for innovative technologies to solve these problems. In recent years, the interest of the scientific community has focused on violet–blue light at 405 nm (VBL405). This study aimed to assess the VBL405 efficiency in reducing microbial growth on surfaces and air. This descriptive study run between July and October 2020. Petri dishes were contaminated with P. aeruginosa, E. coli, S. aureus, S. typhimurium, K. pneumoniae and were placed at 2 and 3 m from a LED light source having a wavelength peak at 405 nm and an irradiance respectively of 967 and 497 μW/cm2. Simultaneously, the air in the room was sampled for 5 days with two air samplers (SAS) before and after the exposition to the VBL405 source. The highest microbial reduction was reached 2 m directly under the light source: S. typhimurium (2.93 log10), K. pneumoniae (2.30 log10), S. aureus (3.98 log10), E. coli (3.83 log10), P. aeruginosa (3.86 log10). At a distance of 3 m from the light source, the greatest reduction was observed for S. aureus (3.49 log10), and P. aeruginosa (3.80 log10). An average percent microbial reduction of about 70% was found in the sampled air after 12 h of exposure to VBL405. VBL405 has proven to contrast microbial growth on the plates. Implementing this technology in the environment to provide continuous disinfection and to control microbial presence, even in the presence of people, may be an innovative solution.