University Paris-Est, French Agency for Food, Environmental and Occupational Health and Safety (Anses), Laboratory for Animal Health, Maisons-Alfort, France.
Laboratoire Départemental d'Analyse et de Recherche de Dordogne, Coulounieix Chamiers, France.
PLoS One. 2018 Nov 26;13(11):e0207614. doi: 10.1371/journal.pone.0207614. eCollection 2018.
Surveillance of bovine tuberculosis (bTB) is partly based on the sanitary inspection of carcasses at the abattoir to detect bTB-like lesions which, in compliance with EU recommendations, are analysed by bacteriology and histopathology to disclose Mycobacterium bovis (or M. caprae) infection. Moreover, since 2012, a PCR method with similar sensitivity and specificity values of histopathology and bacteriology respectively is additionally employed in France, partially compensating for the weaknesses of classical diagnostic methods. We analysed a collection of bTB-like lesions from cattle presenting positive histological results albeit with negative PCR results. We present here the results of these samples, recovered from 292 animals culled between 2013 and 2016, analysed with a second line molecular diagnosis approach that consists in a combination of PCRs targeting the M. tuberculosis-M. avium complexes as well as the Mycobacterium genus and sequencing of hsp65 gene. These molecular analyses disclosed to identify the presence of non-tuberculous bacteria which could be responsible for most of these non-specific TB lesions: non tuberculous mycobacteria (24%) or Actinomycetales (56%) such as Rhodococcus equi (53%); 24% of the samples were negative. M. bovis -or any other MTBC members- was neither detected by molecular methods nor isolated in any of them at the end of the 3 months of culture. In conclusion, these results highlight the lack of specificity of histopathology and the usefulness of a first line PCR with a second line molecular diagnostic test to circumvent it. This diagnostic strategy makes it possible to reduce the number of suspect bTB cases raised at the abattoir or shortening their lock-up periods. By simplifying diagnostic schemes, the use of this tool could improve bTB surveillance and make eradication programs more efficient in the future.
牛结核病（bTB）的监测部分基于屠宰场对胴体的卫生检查，以检测类似 bTB 的病变。根据欧盟的建议，这些病变通过细菌学和组织病理学分析来揭示牛分枝杆菌（或 M. caprae）感染。此外，自 2012 年以来，法国还采用了一种与细菌学和组织病理学具有相似灵敏度和特异性值的 PCR 方法，部分弥补了经典诊断方法的弱点。我们分析了一组来自牛的类似 bTB 的病变，这些病变的组织学结果呈阳性，但 PCR 结果为阴性。我们在这里介绍了这些样本的结果，这些样本来自 2013 年至 2016 年间扑杀的 292 头动物，通过二线分子诊断方法进行了分析，该方法包括针对结核分枝杆菌-鸟分枝杆菌复合体以及分枝杆菌属的 PCR 组合和 hsp65 基因测序。这些分子分析显示，这些非特异性 TB 病变中的大多数是由非结核分枝杆菌（24%）或放线菌（56%）引起的，例如马红球菌（53%）；24%的样本为阴性。在培养的 3 个月结束时，无论是通过分子方法还是分离都没有检测到牛分枝杆菌或任何其他 MTBC 成员。总之，这些结果强调了组织病理学的非特异性以及使用一线 PCR 和二线分子诊断测试来规避它的必要性。这种诊断策略可以减少屠宰场提出的疑似 bTB 病例的数量或缩短其锁定期。通过简化诊断方案，该工具的使用可以提高 bTB 监测的效率，并使未来的根除计划更加有效。
