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Forensic evaluation of two nucleic acid extraction systems and validation of a RT-qPCR protocol for identification of SARS-CoV-2 in post-mortem nasopharyngeal swabs

ABSTRACT: The COVID-19 outbreak has represented a challenge for the international scientific community and particularly for forensic sciences. The lack of Coronavirus post-mortem testing led the National Institute of Toxicology and Forensic Sciences (INTCF) from Spain to verify the performance and utility of a quantitative reverse transcription PCR (RT-qPCR) clinical diagnosis protocol for SARS-CoV-2 detection (TaqPath™ COVID-19 CE-IVD RT-PCR Kit), to shed light on the cause of death (COD) in potentially COVID-19 cases in judicial autopsies. Two different RNA extraction methods were also tested (EZ1® DSP Virus Kit on the EZ1® Advanced XL robot versus MagMAX™ Viral/Pathogen Nucleic Acid Isolation Kit) regarding extraction efficiency, precision and contamination. RT-qPCR was evaluated for precision, specificity, limit of detection and concordance. Both the automated and the manual RNA extraction procedures showed good efficiency, but the automated virus extraction by bio-robot produced more reproducible results than the manual extraction. The SARS-CoV-2 RT-qPCR assay showed high sensitivity with a detection limit up to 10 copies/reaction and high specificity, as no cross-reactivity was detected between any of the 12 different RNA viruses tested, including three types of coronaviruses (SARS-CoV, NL63 and 229E). Reproducibility and repeatability of the studied method as well as concordance with other SARS-CoV-2 molecular detection protocols were also demonstrated.

SUBMITTER: Barrio P

PROVIDER: S-EPMC8016541 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Introduction The porcine reproductive and respiratory syndrome virus (PRRSV) continues to challenge swine production in the US and most parts of the world. Effective PRRSV surveillance in swine herds can be challenging, especially because the virus can persist and sustain a very low prevalence. Although weaning-age pigs are a strategic subpopulation in the surveillance of PRRSV in breeding herds, very few sample types have been validated and characterized for surveillance of this subpopulation. The objectives of this study, therefore, were to compare PRRSV RNA detection rates in serum, oral swabs (OS), nasal swabs (NS), ear-vein blood swabs (ES), and family oral fluids (FOF) obtained from weaning-age pigs and to assess the effect of litter-level pooling on the reverse transcription-quantitative polymerase chain reaction (RT-qPCR) detection of PRRSV RNA. Methods Three eligible PRRSV-positive herds in the Midwestern USA were selected for this study. 666 pigs across 55 litters were sampled for serum, NS, ES, OS, and FOF. RT-qPCR tests were done on these samples individually and on the litter-level pools of the swabs. Litter-level pools of each swab sample type were made by combining equal volumes of each swab taken from the pigs within a litter. Results Ninety-six piglets distributed across 22 litters were positive by PRRSV RT-qPCR on serum, 80 piglets distributed across 15 litters were positive on ES, 80 piglets distributed across 17 litters were positive on OS, and 72 piglets distributed across 14 litters were positive on NS. Cohen's kappa analyses showed near-perfect agreement between all paired ES, OS, NS, and serum comparisons (). The serum RT-qPCR cycle threshold values (Ct) strongly predicted PRRSV detection in swab samples. There was a ≥ 95% probability of PRRSV detection in ES-, OS-, and NS pools when the proportion of positive swab samples was ≥ 23%, ≥ 27%, and ≥ 26%, respectively. Discussion ES, NS, and OS can be used as surveillance samples for detecting PRRSV RNA by RT-qPCR in weaning-age pigs. The minimum number of piglets to be sampled by serum, ES, OS, and NS to be 95% confident of detecting ≥ 1 infected piglet when PRRSV prevalence is ≥ 10% is 30, 36, 36, and 40, respectively.

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Forensic evaluation of two nucleic acid extraction systems and validation of a RT-qPCR protocol for identification of SARS-CoV-2 in post-mortem nasopharyngeal swabs

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