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BackgroundThe analysis of transmission of tuberculosis (TB) is challenging in areas with a large migrant population. Standard genotyping may fail to differentiate transmission within the host country from new importations, which is key from an epidemiological perspective.AimTo propose a new strategy to simplify and optimise cross-border surveillance of tuberculosis and to distinguish between recent transmission in the host country and new importationsMethodsWe selected 10 clusters, defined by 24-locus mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR), from a population in Spain rich in migrants from eastern Europe, north Africa and west Africa and reanalysed 66 isolates by whole-genome sequencing (WGS). A multiplex-allele-specific PCR was designed to target strain-specific marker single nucleotide polymorphisms (SNPs), identified from WGS data, to optimise the surveillance of the most complex cluster.ResultsIn five of 10 clusters not all isolates showed the short genetic distances expected for recent transmission and revealed a higher number of SNPs, thus suggesting independent importations of prevalent strains in the country of origin. In the most complex cluster, rich in Moroccan cases, a multiplex allele-specific oligonucleotide-PCR (ASO-PCR) targeting the marker SNPs for the transmission subcluster enabled us to prospectively identify new secondary cases. The ASO-PCR-based strategy was transferred and applied in Morocco, demonstrating that the strain was prevalent in the country.ConclusionWe provide a new model for optimising the analysis of cross-border surveillance of TB transmission in the scenario of global migration.

背景

在移民人口众多的地区，分析结核病（TB）的传播具有挑战性。标准基因分型可能无法区分宿主国内的传播与新的输入，从流行病学角度来看，这是关键。

目的

提出一种新策略，以简化和优化跨境结核病监测，并区分宿主国内的近期传播和新的输入。

方法

我们从一个移民来自东欧、北非和西非的西班牙人群中选择了 10 个由 24 个基因座分枝杆菌间隔重复单元-可变数串联重复（MIRU-VNTR）定义的簇，并通过全基因组测序（WGS）重新分析了 66 个分离株。设计了一种多重等位基因特异性 PCR，以靶向从 WGS 数据中识别出的菌株特异性标记单核苷酸多态性（SNP），以优化最复杂簇的监测。

结果

在 10 个簇中的 5 个中，并非所有分离株都表现出最近传播预期的短遗传距离，并且显示出更多的 SNP，因此表明在原籍国独立输入了流行菌株。在摩洛哥病例丰富的最复杂簇中，一种针对传播亚簇标记 SNP 的多重等位基因特异性寡核苷酸-PCR（ASO-PCR）使我们能够前瞻性地识别新的继发性病例。基于 ASO-PCR 的策略在摩洛哥得到了转移和应用，证明该菌株在该国流行。