Cuella-Martin Isabel, Semuto Ngabonziza Jean Claude, Torrea Gabriela, Meehan Conor Joseph, Mulders Wim, Ushizimpumu Bertin, De Weerdt Louise, Keysers Jelle, De Rijk Willem Bram, Decroo Tom, De Jong Bouke C, Rigouts Leen
Department of Biomedical Sciences, Mycobacteriology Unit, Institute of Tropical Medicine, Antwerp, Belgium.
Department of Biomedical Sciences, Mycobacteriology Unit, Institute of Tropical Medicine, Antwerp, Belgium; Research Innovation and Data Science Division, Rwanda Biomedical Centre; Department of Clinical Biology, University of Rwanda, Kigali, Rwanda.
Int J Mycobacteriol. 2023 Jul-Sep;12(3):274-281. doi: 10.4103/ijmy.ijmy_103_23.
The World Health Organization-endorsed phenotypic and genotypic drug-susceptibility testing (gDST/pDST) assays for the detection of rifampicin-resistant (RR) tuberculosis (TB), may miss some clinically relevant rpoB mutants, including borderline mutations and mutations outside the gDST-targeted hotspot region. Sequencing of the full rpoB gene is considered the reference standard for rifampicin DST but is rarely available in RR-TB endemic settings and when done indirectly on cultured isolates may not represent the full spectrum of mutations. Hence, in most such settings, the diversity and trends of rpoB mutations remain largely unknown.
This retrospective study included rpoB sequence data from a longitudinal collection of RR-TB isolates in Rwanda across 30 years (1991-2021).
Of 540 successfully sequenced isolates initially reported as RR-TB, 419 (77.6%) had a confirmed RR conferring mutation. The Ser450 Leu mutation was predominant throughout the study period. The Val170Phe mutation, not covered by rapid gDST assays, was observed in only four patients, three of whom were diagnosed by pDST. Along with the transition from pDST to rapid gDST, borderline RR-associated mutations, particularly Asp435Tyr, were detected more frequently. Borderline mutants were not associated with HIV status but presented lower odds of having rpoA-C compensatory mutations than other resistance-conferring mutations.
Our analysis showed changes in the diversity of RR-TB conferring mutations throughout the study period that coincided with the switch of diagnostic tools to rapid gDST. The study highlights the importance of rapid molecular diagnostics reducing phenotypic bias in the detection of borderline rpoB mutations while vigilance for non-rifampicin resistance determinant region mutations is justified in any setting.
世界卫生组织认可的用于检测利福平耐药（RR）结核病（TB）的表型和基因型药敏试验（gDST/pDST）检测方法，可能会遗漏一些临床相关的rpoB突变，包括临界突变和gDST靶向热点区域以外的突变。rpoB全基因测序被认为是利福平药敏试验的参考标准，但在RR-TB流行地区很少可用，并且当间接对培养的分离株进行测序时，可能无法代表突变的全貌。因此，在大多数此类环境中，rpoB突变的多样性和趋势在很大程度上仍然未知。
这项回顾性研究纳入了卢旺达30年（1991 - 2021年）间RR-TB分离株纵向收集的rpoB序列数据。
在最初报告为RR-TB的540株成功测序的分离株中，419株（77.6%）有确诊的RR赋予突变。Ser450 Leu突变在整个研究期间占主导地位。快速gDST检测未涵盖的Val170Phe突变仅在4例患者中观察到，其中3例通过pDST诊断。随着从pDST向快速gDST的转变，临界RR相关突变，特别是Asp435Tyr，被更频繁地检测到。临界突变与HIV状态无关，但与其他耐药赋予突变相比，具有rpoA-C补偿性突变的几率更低。
我们的分析表明，在整个研究期间，RR-TB赋予突变的多样性发生了变化，这与诊断工具向快速gDST的转变相吻合。该研究强调了快速分子诊断在减少临界rpoB突变检测中的表型偏差方面的重要性，同时在任何环境中对非利福平耐药决定区突变保持警惕都是合理的。
