Evaluation of Filters for the Sampling and Quantification of RNA Phage Aerosols

This study exploits the virulent bacteriophages phi 6 (dsRNA) and MS2 (ssRNA) as surrogates for airborne RNA viruses. Two different filter types, polytetrafluoroethylene (PTFE) and polycarbonate (PC), were tested for their efficiency in collecting aerosolized RNA phages. Two commercial kits were tested for total RNA isolation. Also, heat shock treatments were performed in three different media to obtain the most favorable conditions for reverse transcription assays of dsRNA. Our findings suggest that PC filters are more suitable to recover infectious airborne RNA viruses as determined by plaque assays. Both types of filters were equally efficient in recovering RNA from aerosolized phage phi 6 as established by qRT-PCR. Viral samples should be treated with QIAamp Viral RNA Mini Kit and a 5 min heat shock treatment at 110 degrees C in TE buffer before RT-PCR to maximize detection of phage phi 6. Overall, the infectivity of the recovered phages was severely affected by the aerosolization/air sampling process and the presence of RNA viruses in air samples should be determined by qRT-PCR.