A novel RdRp-based colorimetric RT-LAMP assay for rapid and sensitive detection of SARS-CoV-2 in clinical and sewage samples from Pakistan

Virus Res. 2021 Sep:302:198484. doi: 10.1016/j.virusres.2021.198484. Epub 2021 Jun 17.

Abstract

Novel corona virus SARS-CoV-2, causing coronavirus disease 2019 (COVID-19), has become a global health challenge particularly for developing countries like Pakistan where overcrowded cities, inadequate sanitation, little health awareness and poor socioeconomic conditions exist. The SARS-CoV-2 has been known to spread primarily through direct contact and respiratory droplets. However, detection of SARS-CoV-2 in stool and sewage have raised the possibility of fecal-oral mode of transmission. Currently, quantitative reverse-transcriptase PCR (qRT-PCR) is the only method being used for SARS-CoV-2 detection, which requires expensive instrumentation, dedicated laboratory setup, highly skilled staff, and several hours to report results. Considering the high transmissibility and rapid spread, a robust, sensitive, specific and cheaper assay for rapid SARS-CoV-2 detection is highly needed. Herein, we report a novel colorimetric RT-LAMP assay for naked-eye detection of SARS-COV-2 in clinical as well as sewage samples. Our SARS-CoV-2 RdRp-based LAMP assay could successfully detect the virus RNA in 26/28 (93%) of RT-PCR positive COVID-19 clinical samples with 100% specificity (n = 7) within 20 min. We also tested the effect of various additives on the performance of LAMP assay and found that addition of 1 mg/ml bovine serum albumin (BSA) could increase the sensitivity of assay up to 101 copies of target sequence. Moreover, we also successfully applied this assay to detect SARS-CoV-2 in sewage waters collected from those areas of Lahore, a city of Punjab province of Pakistan, declared as virus hotspots by local government. Our optimized LAMP assay could provide a sensitive first tier strategy for SARS-CoV-2 screening and can potentially help diagnostic laboratories in better handling of high sample turnout during pandemic situation. By providing rapid naked-eye SARS-CoV-2 detection in sewage samples, this assay may support pandemic readiness and emergency response to any possible virus outbreaks in future.

Keywords: COVID-19; LAMP; RdRp; SARS-CoV-2; sewage water.

MeSH terms

  • COVID-19 / diagnosis*
  • COVID-19 / virology
  • COVID-19 Testing
  • Colorimetry
  • Feces / virology
  • Humans
  • Mass Screening
  • Molecular Diagnostic Techniques / methods*
  • Nucleic Acid Amplification Techniques / methods*
  • Pakistan / epidemiology
  • Pandemics*
  • RNA, Viral / genetics
  • RNA-Dependent RNA Polymerase / metabolism
  • SARS-CoV-2 / genetics
  • SARS-CoV-2 / isolation & purification*
  • Sensitivity and Specificity
  • Sewage / virology*

Substances

  • RNA, Viral
  • Sewage
  • RNA-Dependent RNA Polymerase

Supplementary concepts

  • LAMP assay