北京市某中学结核病聚集性疫情的实验室鉴定结果分析

Laboratory identification of tuberculosis outbreak in a middle school in Beijing

目的 采用实验室检测技术,分析2018年10月至2019年1月在北京市某中学结核病聚集性疫情中分离获得的菌株,为疫情的溯源和学校结核病防控提供一定的科学依据。方法 依据首发患者线索,对其及203名密切接触者实施实验室检测,包括结核抗体检测、γ-干扰素检测、痰涂片和痰培养,以及阳性菌株菌种鉴定、分子分型和成簇性分析等实验室研究工作。结果 以结核分枝杆菌实验室培养阳性为金标准,确定包括首发患者在内的共6例结核病确诊病例。在培养阳性组中,免疫学检查显示结核抗体阳性率为50.0%,γ-干扰素阳性率为66.7%。6株阳性菌株提取DNA后,采用多位点PCR菌种鉴定均为结核分枝杆菌,同时经12位点可变数目串联重复序列分析(MLVA)及间隔区寡核苷酸分型检测分析,结果显示5株为北京基因型,1株无结果。MLVA结果为4株12位点拷贝数完全一致,1株仅在Qub11a位点上相差1.6个拷贝,另外1株在ETR-A位点和MIRU27位点各相差1个拷贝数,其余位点拷贝数均相同。结论 本次实验室鉴定出的6株阳性菌株,均为结核分枝杆菌,其中5株为北京基因型。4株样品菌株间存在较大同源性,存在近期传播可能,但需进一步的测序分析。

Objective To analyze the characteristics of the Mycobacterium tuberculosis isolates from a tuberculosis(TB)outbreak in a middle school in Beijing, from October 2018 to January 2019 with Laboratory detection techniques and provide evidence for the tracing, prevention and control of the TB epidemic. Methods A laboratory test was conducted for the index case and 203 close contacts, including M. tuberculosis antibody detection, γ-interferon detection, sputum smear and culture, as well as the identification, molecular typing and cluster analysis of positive strains. Results According to the gold standard for culture positive in laboratory, a total of 6 TB cases, including the index cases, were identified. In the culture-positive group,the immunological examination showed that the positive rate of M. tuberculosis antibody was 50%, and the positive rate ofγ-interferon was 66.7%. After DNA extraction of the 6 positive strains, all the strains were identified as M. tuberculosis by multi-loci PCR. At the same time, and the 6 strains were detected by 12 loci variable number tandem repeat sequence analysis(MLVA) and the spacer(Spoligotyping) oligonucleotide method. The results showed that 5 strains belonged to Beijing genotype, and 1 strain had no result. It was found that 4 strains had same VNTR pattern of 12 loci, and one strain had 1.6 variant in Qub11 a locus, another strain showed a difference of one copy number at ETR-A and MIRU27, but the copy numbers at other sites were same. Conclusion The 6 positive isolates identified in this laboratory were all M. tuberculosis, and 5 strains belonged to Beijing genotype. MLVA typing analysis indicated that 4 strains shared high homology, suggesting the possibility of recent transmission and the necessity of further sequencing analysis.