Dry Swab Method of sample collection for SARS-CoV2 testing can be used for culturing virus

Ram, Sushma; Enayathullah, M. Ghalib; Parekh, Yash; Tallapaka, Karthik Bharadwaj; Mishra, Rakesh K; Bokara, Kiran Kumar

Back ground Earlier studies suggested the use of dry swab method for SARS-CoV-2 detection as it does not need VTM and subsequent RNA extraction step making the process cheaper, safer and faster. In this study we explore whether the virus in the dry swab is viable and can be cultured and propagated. Method Swabs were spiked with SARS-CoV-2 and stored in three different conditions: a) as dry swab (SD, eluted in 1 mL DMEM), b) in 1 mL of Viral Transport Medium (SVTM), and c) in 1 mL of Tris-EDTA buffer (STE). The sample groups were stored either at room temperature (RT, 25°C±1°C) or at 4°C for 1, 4, 8, 12, 24, 48 and 72 hours before being used as viral inoculums for the propagation studies in Vero cells. Results The RT-qPCR data suggests that SD incubated both at RT and 4°C harbors viral particles that are viable and culturable at par with SVTM and STE. Conclusion The dry swab method, in addition to its advantages in detection of the virus, also renders viable viral particles that can be cultured and propagated.