CSIR-Centre for Cellular and Molecular Biology (CSIR-CCMB), Hyderabad, India.
J Biosci. 2021;46(4). doi: 10.1007/s12038-021-00216-9.
The rapid spread and evolution of various strains of SARS-CoV-2, the virus responsible for COVID-19, continues to challenge the disease controlling measures globally. Alarming concern is, the number of second wave infections surpassed the first wave and the onset of severe symptoms manifesting rapidly. In this scenario, testing of maximum population in less time and minimum cost with existing diagnostic amenities is the only possible way to control the spread of the virus. The previously described RNA extraction-free methods using dry swab have been shown to be advantageous in these critical times by different studies. In this work, we show the temporal stability and performance of the dry swab viral detection method at two different temperatures. Contrived dry swabs holding serially diluted SARS-CoV-2 strains A2a and A3i at 25°C (room temperature; RT) and 4°C were subjected to direct RT-PCR and compared with standard VTM-RNA based method. The results clearly indicate that dry swab method of RNA detection is as efficient as VTM-RNA-based method in both strains, when checked for up to 72 h. The lesser C values of dry swab samples in comparison to that of the VTM-RNA samples suggest better sensitivity of the method within 48 h of time. The results collectively suggest that dry swab samples are stable at RT for 24 h and the detection of SARS-CoV-2 RNA by RT-PCR do not show variance from VTM-RNA. This extraction free, direct RT-PCR method holds phenomenal standing in the present life-threatening circumstances due to SARS-CoV-2.
SARS-CoV-2 病毒（引发 COVID-19 疫情的病毒）的各种毒株迅速传播和演变，继续对全球疾病控制措施构成挑战。令人担忧的是，第二波感染人数超过了第一波，且严重症状迅速出现。在这种情况下，利用现有的诊断手段，以最快的速度、最低的成本对最大人群进行检测，是控制病毒传播的唯一途径。之前的研究表明，使用干拭子的无 RNA 提取方法在这些关键时刻具有优势。在这项工作中，我们展示了在两种不同温度下干拭子病毒检测方法的时间稳定性和性能。在 25°C（室温；RT）和 4°C 下，将含有连续稀释 SARS-CoV-2 株 A2a 和 A3i 的干拭子进行直接 RT-PCR，并与基于标准 VTM-RNA 的方法进行比较。结果清楚地表明，在检查长达 72 小时时，干拭子 RNA 检测方法与基于 VTM-RNA 的方法一样有效，两种菌株都是如此。与 VTM-RNA 样本相比，干拭子样本的 C 值较小，表明该方法在 48 小时内的灵敏度更高。结果表明，在 RT 下，干拭子样本在 24 小时内稳定，RT-PCR 检测 SARS-CoV-2 RNA 与 VTM-RNA 没有差异。由于 SARS-CoV-2 的存在，这种无需提取、直接 RT-PCR 的方法在当前危及生命的情况下具有重要意义。
