Feasibility of using real-time optical methods for detecting the presence of viable bacteria aerosols at low concentrations in clean room environments

An experimental investigation was carried out to determine the agreement between two methods of viable bacteria aerosol detection. Various amounts of Bacillus globigii (BG) spores were aerosolized in 1-s bursts into a HEPA-filtered air stream and sampled simultaneously with a fluorescence aerosol particle sensor (FLAPS) and a slit to agar biological air sampler. The slit sampler incorporated 150-mm malt extract culture plates, which were incubated at 37°C for at least 12 h before culturable BG particles were counted in terms of colony-forming units (CFU). A relationship between CFU and optically detected viable bacteria particles was determined as culturable particle concentrations decreased. Through further analytical procedures, the FLAPS showed a limit of detection (LOD) of 4.2 bacterial particle/2.5 l of sampled air or 1.7 × 10³ m^-3. This real-time bacteria aerosol monitor could be used to detect burst contamination events during a surgical procedure. The technology may be used for developing a dose- response relationship between bacterial particle exposure and infection, a tool potentially helpful in determining patient risk.