新型冠状病毒核酸检测混采阳性样本的溯源检测和分析

Retroactive detection and analysis of mixed positive samples in nucleic acid testing for SARS-CoV-2

目的对某新型冠状病毒(以下简称新冠病毒)核酸检测阳性的混采鼻咽拭子样本进行溯源检测和分析,为新型冠状病毒感染(以下简称新冠感染)疫情大规模核酸筛查混采阳性样本的溯源提供参考。方法用实时荧光RTPCR方法对某一批次混采A+B组2合1鼻咽拭子新冠病毒核酸阳性样本及同批次复核C、D单管鼻咽拭子新冠病毒核酸阳性样本进行复测,并对混采A+B组阳性样本进行污染鉴定、突变株检测和全基因组测序实验。将测序结果与同批次检出的C、D单管阳性样本序列进行比对分析。结果A+B组混采及单管C、D单管样本复测均阳性;A+B混采样本排除DNA污染;A+B混采样本及C、D单管阳性样本中新冠病毒均为德尔塔变异株类似株(B.1.617.2突变株),全基因组序列一致性为100%,这三件阳性样本的病毒来源一致。结论新冠感染疫情大规模人群核酸筛查出现混采阳性而复核单管阴性时,需利用多种实验方法对混采阳性和其他相关样本检测,结合流调资料进行溯源分析,降低感染病例漏检率。

Objective To test and analyze retroactively a certain batch of mixed positive nasopharyngeal samples in nucleic acid testing for SARS-CoV-2 so as to provide reference for the source of the mixed positive samples in large-scale nucleic acid screening of COVID-19 epidemic situation.Methods The positive samples for two-in-one nasopharynx swabs of group A+B in a certain batch and single-tube nasopharynx swabs of C and D in the same batch were retested by real-time fluorescent RTPCR.Contamination identification、mutant detection and whole genome sequencing were performed analysis on the positive samples of group A+B.The sequencing result were compared with the sequences of C and D single-tube positive samples from the same batch.Results The sample of A+B mixed mining and single tube C and D were all positive.A+B mixed sample was excluded from DNA contamination;A+B mixed samples and C and D single-tube positive samples were identified as Delta variant strains(SARS-CoV-21.617.2 mutant).The genome sequence consistency was 100%and the three positive samples of the virus come from the same source.Conclusions When nucleic acid screening of large-scale population of COVID-19 epidemic situation appears mixed positive but single negative,the mixed positive and other related samples should be detected by various experimental method.The source analysis should be carried out combining with the data of epidemiological investigation data,reducing the rate of missed detection of infection cases.