Published time: 09 June 2020
Authors: Chung-Guei Huang, Kuo-Ming Lee, Mei-Jen Hsiao, Shu-Li Yang, Peng-Nien Huang, Yu-Nong Gong, Tzu-Hsuan Hsieh, Po-Wei Huang, Ya-Jhu Lin, Yi-Chun Liu, Kuo-Chien Tsao, Shin-Ru Shih
Keywords: genome, SARS-CoV-2, virus isoloation, infectivity.
Real-time reverse transcription (RT)-PCR is currently the most sensitive method to detect severe acute respiratory syndrome coronavirus 2 virus (SARS-CoV-2) that causes coronavirus disease 2019 (COVID-19). However, the correlation between detectable viral RNA and culturable virus in clinical specimens remains unclear. Here, we performed virus culture for 60 specimens that were confirmed to be positive for SARS-CoV-2 RNA by real-time RT-PCR. The virus could be successfully isolated from 12 throat and nine nasopharyngeal swabs, and two from sputum specimens. The lowest copy number required for virus isolation was determined to be 5.4, 6.0, and 5.7 log10 genome copies/mL sample for detecting the nsp12, E, and N gene, respectively. We further examined the correlation of genome copy number and virus isolation in different regions of the viral genome, demonstrating that culturable specimens are characterized by high copy numbers with a linear correlation observed between copy numbers of amplicons targeting structural and non-structural regions. Overall, these results indicate that in addition to the copy number, the integrity of the viral genome should be considered when evaluating the infectivity of clinical SARS-CoV-2 specimens.
Culture-based virus isolation to evaluate potential infectivity of clinical specimens tested for COVID-19