Mycobacterium bovis causes tuberculosis (TB) in cattle, which in turn can transmit the pathogen to humans. Tuberculosis in dairy cattle is of particular concern where the consumption of raw milk and dairy products is customary. Baja California (BCA), Mexico, presents high prevalence of TB in both cattle and humans, making it important to investigate the molecular epidemiology of the disease in the region. A long-term study was undertaken to fully characterize the diversity of M. bovis genotypes circulating dairy cattle, cheese, and humans in BCA by whole-genome sequencing (WGS). Tissue and cheese samples were collected in BCA over a two-year period and sent to the laboratory for mycobacterial culture, histology, direct PCR, and WGS. A total of 445 and 314 tissue and cheese samples, respectively, were collected. For tissue, isolation was positive for 86.8%, direct PCR detection was 90%, and histology confirmed 85.9% as mycobacteriosis-compatible. For cheese, the isolation rate was 2.5% and PCR detected 5.7%. Overall, there was agreement between diagnostic tests. Subsequently, a total of 345 whole-genome sequences were obtained; and phylogenetic analysis placed these isolates in 10 major clades. Single nucleotide polymorphism (SNP) analysis revealed putative transmission clusters where the pairwise SNP distance between isolates from different dairies was ≤ 3 SNP. Also, human and/or cheese isolates were within 8.45 (range 0-17) and 5.8 SNPs (range 0-15), respectively, from cattle isolates. Finally, a comparison between the genotypes obtained in this study and those reported previously showed that full characterization of the genetic diversity of M. bovis in the region was achieved. In conclusion, WGS provided evidence of ongoing local transmission of M. bovis among the dairies in this high-TB burden region of BCA, as well as close relationships between isolates from humans, cheese, and these cattle. This confirms the need for a coordinated One Health approach in addressing the elimination of TB in animals and humans.

中文翻译：

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通过 WGS 在墨西哥下加利福尼亚州的牛、奶酪和人类中追踪牛分枝杆菌感染

牛分枝杆菌会导致牛患结核病 (TB)，而后者又可以将病原体传播给人类。在习惯食用生奶和乳制品的情况下，奶牛的结核病尤其令人担忧。墨西哥下加利福尼亚州 (BCA) 的牛和人类结核病患病率很高，因此调查该地区疾病的分子流行病学非常重要。进行了一项长期研究，以通过全基因组测序 (WGS) 全面表征 BCA 中循环奶牛、奶酪和人类的牛分枝杆菌基因型的多样性。组织和奶酪样本在 BCA 中收集了两年时间，然后送到实验室进行分枝杆菌培养、组织学、直接 PCR 和 WGS。总共分别收集了 445 和 314 个组织和奶酪样品。对于纸巾，分离阳性率为 86.8%，直接 PCR 检测为 90%，组织学证实 85.9% 为分枝杆菌兼容。对于奶酪，分离率为 2.5%，PCR 检测率为 5.7%。总体而言，诊断测试之间存在一致性。随后，总共获得了345条全基因组序列；系统发育分析将这些分离株置于 10 个主要进化枝中。单核苷酸多态性 (SNP) 分析揭示了假定的传播簇，其中来自不同乳制品的分离株之间的成对 SNP 距离≤ 3 SNP。此外，与牛分离物的人和/或奶酪分离物分别在 8.45（范围 0-17）和 5.8 个 SNP（范围 0-15）内。最后，本研究中获得的基因型与先前报道的基因型之间的比较表明，对 M. 该地区的 bovis 已实现。总之，WGS 提供了证据表明牛分枝杆菌在这个 BCA 结核病高负担区域的奶牛场中持续本地传播，以及从人类、奶酪和这些牛身上分离出来的菌株之间存在密切关系。这证实了在消除动物和人类结核病方面需要采取协调一致的 One Health 方法。