Development of an improved sampling method for concentrating viruses from bioaerosols

![CDATA[Introduction: Bioaerosols are a potential source of food contamination with microorganisms, including viruses. Among the most effective platforms to capture viruses from bioaerosols is the SKC Biosampler, an all-glass impinger employing a high-volume sonic flow pump to trap aerosolized particles in liquid matrices approximately 20 ml in volume. However, this relatively large sample volume limits the sensitivity of molecular detection methods in which only small sample volumes are typically analyzed. Purpose: Here, the performance of a novel modification to SKC Biosamplers compatible with molecular detection strategies was tested. IRA-900 anion exchange resin was added to the SKC BioSampler liquid matrix to adsorb and concentrate negatively charged MS2 and ɸ6 bacteriophages (also surrogates of human enteric viruses and influenza virus, respectively). Methods: MS2 and ɸ6 (10-3 to 106 PFU/ml inocula) in PBS were aerosolized to particle concentrations of 5 mg/m3 in a HEPA-filtered bioaerosolization chamber. For each experiment (performed in triplicate), two SKC BioSamplers containing 20 ml of PBS with and without 0.5 g of IRA-900 were co-located in the chamber and each attached to a pump calibrated to sample 500 liters of air in 40 min. RNA was isolated from the PBS and IRA-900 for real time reverse transcriptase PCR (RT-PCR) analyses. Results: The addition of IRA-900 to SKC BioSamplers markedly improved RT-PCR detection sensitivity for MS2 by an average of 8.15× (P < 0.05), and allowed for reliable detection of 1 log fewer MS2 (102 PFU/ml MS2 inoculum) compared to direct testing of unmodified SKC BioSamplers. For ɸ6, the improvement in detection sensitivity was not as pronounced as with MS2 (average of 2.08 × improvement) and allowed for 103 PFU/ml of the ɸ6 nebulized inoculum to be detected. Significance: The addition of IRA-900 to SKC BioSamplers improved the sensitivity of RT-PCR detection with the tested aerosolized bacteriophages.]]