Investigating the susceptibility of laboratory-generated bacterial aerosols to antimicrobial 405 nm light

Airborne transmission of infectious organisms is a major concern within the healthcare environment. A number of methods for 'whole room' decontamination, such as antimicrobial 405nm light, are being developed, and it is important that efficacy against airborne, as well as surface-deposited contamination is established. This study demonstrates evidence of the dose-response kinetics of airborne bacterial contamination when exposed to 405nm light. Aerosols of Staphylococcus epidermids, 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 405nm 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 (1.8 log₁₀ reduction) achieved with 1-hour exposure to low irradiance 405nm 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). Inactivation using ultraviolet (UV) light was also investigated in order to quantify the comparative efficacy of these antimicrobial light regions.Overall, results have provided early evidence of the susceptibility of bacterial aerosols to antimicrobial 405 nm light. Although less germicidally efficient than UV-light, the benefits of 405 nm light in terms of increased safety for human exposure, provide advantages for a number of applications, including continuous 'whole room' environmental decontamination, where reducing levels of airborne bacteria should contribute to reducing infections arising from airborne contamination.