Modern bioaerosol sampling and analysis techniques that enable rapid detection of low bioagent concentrations in various environments are needed to help us understand the causal relationship between adverse health effects and bioaerosol exposures and also to enable the timely biohazard detection in case of intentional release.We have developed a novel bioaerosol sampler, an electrostatic precipitator with superhydrophobic surface (EPSS), where a combination of electrostatic collection mechanism with superhydrophobic collection surface allows for efficient particle collection, removal, and concentration in water droplets as small as 5 µL. The sampler's performance at different sampling flow rates and sampling times was tested with two common bacteria: Pseudomonas fluorescens and Bacillus subtilis. The collection efficiency was determined using the traditional method of microscopic counting as well as the whole-cell quantitative real-time polymerase chain reaction assay (QPCR). The tests indicated that the new sampler achieves collection efficiency as high as 72%. A combination of the satisfactory collection efficiency and the small collecting water droplet volumes allowed achieving sample concentration rates that exceed 1 × 10 6 . In addition, the collection efficiency for both bacteria obtained by the two different methods was not statistically different, indicating the sampler's compatibility with the PCR-based sample analysis techniques. In addition, the whole-cell QPCR does not require DNA extraction prior to the PCR reaction which offers faster sample processing.Very high concentration rates achieved with the new sampler as well as its compatibility with the QPCR methodology point toward its suitability for detecting low concentrations of airborne bacterial agents in various environments.

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This research investigated whether electrostatic fields can be used to inactivate surface-borne and airborne microorganisms. Vegetative cells of Pseudomonas fluorescens and Bacillus subtilis var. niger were deposited on filters and subjected to electrostatic fields of different strengths and polarities for controlled time periods. In addition, P. fluorescens bacteria, which represent sensitive species, were aerosolized and exposed to electrostatic fields of up to +/- 10 kV/cm. The results have shown that more than 90% of the P. fluorescens cells deposited on the surface of nonconductive filters are inactivated when fields of 15 kV/cm are applied for 30 min or longer. Similar effects were observed when P. fluorescens were exposed to fields of 5 and 10 kV/cm for 2 h. In contrast, the culturability of B. subtilisvar. niger cells exposed under the same conditions did not substantially decrease. Exposure of airborne P. fluorescens to +/- 10 kV/cm for 30 s also did not result in a significant reduction of culturability. This research has shown that specific combinations of electrostatic field strength and exposure time can be used to effectively inactivate certain bacterial cells deposited on nonconductive surfaces. For the investigated conditions, the treatment was not effective for bacteria in the airborne state.

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The laboratory testing of the RCS High Flow bioaerosol sampler showed that the sampler collects 1 microm particles and larger with an efficiency of 50% and higher; the efficiency reaches approximately 100% for particles of 2.5 microm and larger. When considering this result, most of the airborne fungal spores would be collected with an efficiency between 50 and 100%. The field testing, however, indicated that the RCS High Flow sampler recovered from 41 to 71% of microorganisms collected relative to the reference sampler, Biosampler, and this ratio dropped to below 5% during outdoor testing. Thus, while the RCS High Flow sampler offers certain advantages over other samplers for viable bioaerosols--it is lightweight, battery operated, and collects viable microorganisms at a high flow rate directly on agar media, the results obtained may have to be adjusted to avoid potential underestimation of microorganism concentration in the air, especially if sampling is performed outdoors.