Department of Physiology, Wayne State, Detroit, MI 48201, USA.
LimnoTech, 501 Avis Dr., Ann Arbor, MI 48108, USA.
Sci Total Environ. 2023 Sep 1;889:164180. doi: 10.1016/j.scitotenv.2023.164180. Epub 2023 May 16.
Early detection of the COVID-19 virus, SARS-CoV-2, is key to mitigating the spread of new outbreaks. Data from individual testing is increasingly difficult to obtain as people conduct non-reported home tests, defer tests due to logistics or attitudes, or ignore testing altogether. Wastewater based epidemiology is an alternative method for surveilling a community while maintaining individual anonymity; however, a problem is that SARS-CoV-2 markers in wastewater vary throughout the day. Collecting grab samples at a single time may miss marker presence, while autosampling throughout a day is technically challenging and expensive. This study investigates a passive sampling method that would be expected to accumulate greater amounts of viral material from sewers over a period of time. Tampons were tested as passive swab sampling devices from which viral markers could be eluted with a Tween-20 surfactant wash. Six sewersheds in Detroit were sampled 16-22 times by paired swab (4 h immersion before retrieval) and grab methods over a five-month period and enumerated for N1 and N2 SARS-CoV-2 markers using ddPCR. Swabs detected SARS-CoV-2 markers significantly more frequently (P < 0.001) than grab samples, averaging two to three-fold more copies of SARS-CoV-2 markers than their paired grab samples (p < 0.0001) in the assayed volume (10 mL) of wastewater or swab eluate. No significant difference was observed in the recovery of a spiked-in control (Phi6), indicating that the improved sensitivity is not due to improvements in nucleic acid recovery or reduction of PCR inhibition. The outcomes of swab-based sampling varied significantly between sites, with swab samples providing the greatest improvements in counts for smaller sewersheds that otherwise tend to have greater variation in grab sample counts. Swab-sampling with tampons provides significant advantages in detection of SARS-CoV-2 wastewater markers and are expected to provide earlier detection of new outbreaks than grab samples, with consequent public health benefits.
早期发现 COVID-19 病毒，即 SARS-CoV-2，是减轻新疫情传播的关键。随着人们进行未经报告的家庭检测、由于后勤或态度而推迟检测，或完全忽略检测，个人检测的数据越来越难以获得。基于废水的流行病学是一种监测社区的替代方法，同时保持个人匿名；然而，一个问题是，废水中的 SARS-CoV-2 标志物在一天中会发生变化。在单一时间采集随机样本可能会错过标志物的存在，而一整天的自动采样在技术上具有挑战性且昂贵。本研究调查了一种被动采样方法，预计该方法会在一段时间内从污水中积累更多的病毒物质。使用含有吐温-20 表面活性剂的洗涤液从棉塞中洗脱，测试了棉塞作为被动拭子采样装置。在五个月的时间里，对底特律的六个污水流域进行了 16-22 次配对拭子（取回前浸泡 4 小时）和随机样本采集，并使用 ddPCR 对 N1 和 N2 SARS-CoV-2 标志物进行计数。拭子比随机样本更频繁地检测到 SARS-CoV-2 标志物（P<0.001），在检测体积（10mL）中，拭子样本的 SARS-CoV-2 标志物拷贝数比配对的随机样本平均高出两到三倍（p<0.0001）。在拭子洗脱液中未观察到掺入的对照（Phi6）的回收率有显著差异，这表明灵敏度的提高不是由于核酸回收的改善或 PCR 抑制的减少。拭子采样的结果在各个地点之间存在显著差异，对于较小的污水流域，拭子样本在计数方面提供了最大的改善，而这些污水流域的随机样本计数通常变化更大。使用棉塞进行拭子采样在检测 SARS-CoV-2 废水标志物方面具有显著优势，预计比随机样本更早地发现新的疫情爆发，从而带来相应的公共卫生益处。
