Efficacy of antimicrobial 405 nm blue-light for inactivation of airborne bacteria

Airborne transmission of infectious organisms is a considerable concern within the healthcare environment. A number of novel methods for ‘whole room’ decontamination, including antimicrobial 405 nm blue light, are being developed. To date, research has focused on its effects against surface-deposited contamination; however it is important to also establish its efficacy against airborne bacteria. This study demonstrates evidence of the dose-response kinetics of airborne bacterial contamination when exposed to 405 nm light.Bacterial aerosols of Staphylococcus epidermidis, generated using a 6-Jet Collison nebuliser, were introduced into an aerosol chamber designed to maintain prolonged airborne suspension and circulation. Aerosolized bacteria were exposed to increasing doses of 405 nm light, and air samples were extracted from the chamber using a BioSampler liquid impinger, with viability analysed using pour-plate culture. Initial results have demonstrated successful aerosol inactivation, with a 98.4% reduction achieved with 1-hour exposure to low irradiance (11.9 mWcm-2) 405 nm light (P=<0.001). Natural decay of the suspended aerosol was observed, however this was significantly less than achieved with light treatment (P=0.004). Overall, results have provided early evidence of the susceptibility of bacterial aerosols to 405 nm light. Although less germicidally efficient than UV-light, 405 nm light treatment offers benefits in terms of increased safety for human exposure, and eradication of microbes regardless of antibiotic resistance. Such benefits provide advantages for a number of applications including ‘whole room’ environmental decontamination, in which reducing levels of airborne bacteria should reduce the number of infections arising from airborne contamination.