Detection of severe acute respiratory syndrome coronavirus 2 in bioaerosols using digital droplet polymerase chain reaction and loop-mediated isothermal amplification.

Abstract

In the present study, we simulated human passive breathing, sampled severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) bioaerosols, and compared the detection ability of quantitative polymerase chain reaction (qPCR), digital droplet polymerase chain reaction (ddPCR), and loop-mediated isothermal amplification (LAMP). The specificity of the primer set for the LAMP-based detection of SARS-CoV-2 was evaluated, and its sensitivity using the detection threshold in the amplification curve plots was determined. Next, we used an aerosol collection environment and collected solutions containing predetermined concentrations of plasmid containing SARS-CoV-2 N gene, which were dispersed into the environment, using a cyclone sampler. Finally, we compared the ability of qPCR, ddPCR, and LAMP in detecting SARS-CoV-2 in aerosols and stock solutions. After sampling, qPCR, LAMP and ddPCR can amplify the micro viral samples exponentially. By comparing the three assays, it was judged from the results that qPCR had a slightly higher detection limit, detecting 10² copies per μL, and therefore could not be used as a test for trace samples. qPCR, LAMP, and ddPCR were able to detect aerosol samples of 10¹ copies per μL. LAMP was able to qualitatively detect the samples, and ddPCR was able to quantitatively detect samples of this order of magnitude. There were 23.2 that could be used as a quantitative assay. This method can be used in public places or hospitals with limited air circulation to detect aerosol-borne viruses in trace quantities and to provide a rapid early warning.