10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Improvement of Cell Extraction from Filters after Bioaerosol Sampling
INKEN SCHULZE-HESSING, Dierk Pöther, Udo Jäckel, Federal Institute for Occupational Safety and Health
Abstract Number: 355 Working Group: Bioaerosols
Abstract The impact of bioaerosols on ecosystem dynamics and human health is becoming increasingly evident. Therefore, the microorganism concentration and the community structures of bioaerosols in the environment as well as on work places were intensively studied using different sampling methods. However, studies determining the efficiencies of bioaerosol sampling methods are rare. Thus, the aim of this study was to investigate recovery efficiencies of microorganisms from different filter types commonly used in bioaerosol sampling.
Five different microorganisms were applied on polycarbonate (P) filters as well as on glass (G) and quartz (Q) fiber filters. Following application the bioaerosol sampling was simulated and cells were extracted from filters with a paddle blender. The recovery efficiency was determined a) via total cell counting with the fluorescent DNA stain 4',6-diamidino-2-phenylindole and b) fluorometric quantitation of extracted DNA. Scanning electron microscopy (SEM) was performed to investigate detachment of bacteria from the filter surface.
Significant species-specific differences in recovery efficiencies were revealed. DNA quantitation showed that recovery efficiencies ranged from < 1% to 45%. For Pseudomonas nitroreducens applied onto P-filters it was shown that the low recovery rates were mainly the result of insufficient extraction from the filter and attachment of cells to the extraction bags in the paddle blender. SEM pictures revealed bacteria penetrating deeply into the G/Q-fiber filters. However, incubation of exposed G-fiber filters with Proteinase K directly before DNA extraction increased the recovery rates of P. nitroreducens cells significantly from < 1% to 69%. Moreover, the incubation with Proteinase K allows the extraction of all tested cells from G-fiber filters without significant species-specific differences in recovery efficiencies.
In conclusion, our study shows the necessity to investigate bioaerosol sampling characteristics to achieve a reliable assessment of bioaerosol exposure. The application of sampling methods with unknown sampling efficiencies may lead to problems in community analyses by concealing the real composition. We were able to show an improved method for cell extraction from filters allowing increased and species-independent recovery.