Abstract
Upper respiratory samples used to test for SARS-CoV-2 virus may be infectious and present a hazard during transport and testing. A buffer with the ability to inactivate SARS-CoV-2 at the time of sample collection could simplify and expand testing for COVID-19 to non-conventional settings. We evaluated a guanidium thiocyanate-based buffer, eNAT™ (Copan) as a possible transport and inactivation medium for downstream Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) testing to detect SARS-CoV-2. Inactivation of SARS-CoV-2 USA-WA1/2020 in eNAT and in diluted saliva was studied at different incubation times. The stability of viral RNA in eNAT was also evaluated for up to 7 days at room temperature (28°C), refrigerated conditions (4°C) and at 35°C. SARS-COV-2 virus spiked directly in eNAT could be inactivated at >5.6 log10 PFU/ml within a minute of incubation. When saliva was diluted 1:1 in eNAT, no cytopathic effect (CPE) on VeroE6 cells was observed, although SARS-CoV-2 RNA could be detected even after 30 min incubation and after two cell culture passages. A 1:2 (saliva:eNAT) dilution abrogated both CPE and detectable viral RNA after as little as 5 min incubation in eNAT. SARS-CoV-2 RNA from virus spiked at 5X the limit of detection remained positive up to 7 days of incubation in all tested conditions. eNAT and similar guanidinium thiocyanate-based media may be of value for transport, stabilization, and processing of clinical samples for RT-PCR based SARS-CoV-2 detection.
Highlights
The novel coronavirus SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2), the causative agent of Coronavirus induced disease 2019 (COVID19), emerged in Wuhan, China at the end of 2019 and has since infected almost one hundred fifty million people worldwide, causing a global pandemic [1,2,3]
SARS-COV-2 virus spiked directly in eNAT could be inactivated at >5.6 log10 PFU/ml within a minute of incubation
Conclusion eNAT and similar guanidinium thiocyanate-based media may be of value for transport, stabilization, and processing of clinical samples for Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) based SARS-CoV-2 detection
Summary
The novel coronavirus SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2), the causative agent of Coronavirus induced disease 2019 (COVID19), emerged in Wuhan, China at the end of 2019 and has since infected almost one hundred fifty million people worldwide, causing a global pandemic [1,2,3]. Clinical samples obtained for SARS-CoV-2 testing can present a biohazard during transport or processing in a testing laboratory [4]. The CDC recommends that tests for SARS-CoV-2 should be performed inside a biosafety cabinet in a BSL-2 laboratory setting (https://www.cdc.gov/coronavirus/2019-ncov/ lab/lab-biosafety-guidelines.html) to ensure worker safety. These strict testing requirements limit the locations where SARS-CoV-2 assays can be safely performed. A transport buffer that inactivates SARS-CoV-2 while remaining suitable for RT-PCR detection assays would mitigate these safety threats and simplify widespread COVID-19 testing. A buffer with the ability to inactivate SARS-CoV-2 at the time of sample collection could simplify and expand testing for COVID-19 to non-conventional settings
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