Department of Microbiology, National Institute of Tuberculosis and Respiratory Diseases, Mehrauli, New Delhi 110030.
Center for Bio-design and Diagnostics, Translational Health Science and Technology Institute, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Express way, PO box # 04, Faridabad 121001; Department of Bioscience and Biotechnology, Banasthali Vidyapith, P.O. Banasthali Vidyapith, Rajasthan 304022; Department of Experimental Medicine and Biotechnology, Postgraduate Institute of Medical Education and Research, Sector-12, Chandigarh 160012.
Diagn Microbiol Infect Dis. 2020 Apr;96(4):114995. doi: 10.1016/j.diagmicrobio.2020.114995. Epub 2020 Jan 23.
In GenoType MTBDRplus assay [line probe assay (LPA)], when Mycobacterium tuberculosis (M. tuberculosis) sample DNA fails to hybridize to at least 1 rpoB wild-type probe and any mutation probe, it is inferred as rifampin (RIF)-resistant. In this study, we sought to identify such 'inferred' mutations in M. tuberculosis isolates (n = 203) by rpoB gene sequencing and determined their association with phenotypic resistance. D516Y, H526N, L511P mutations were associated with both phenotypically sensitive (59%, n = 38/64) and resistant (23.7%, n = 33/139) antimicrobial susceptibility testing (AST) results, whereas S531W mutation was associated with only RIF-resistant isolates (33%, n = 46/139). These results demonstrated that, at standard drug concentrations, some 'inferred' mutations may be missed by RIF-AST (phenotypically sensitive). The use of LPA permits identification of these RIF-resistant isolates, and incorporation of additional mutation probes (e.g., S531W) could further increase LPA specificity. Further studies are needed to establish the significance of the type of 'inferred' mutation with clinical/treatment outcomes.
在 GenoType MTBDRplus 检测[线探针检测（LPA）]中，如果分枝杆菌（结核分枝杆菌）样本 DNA 未能与至少 1 个 rpoB 野生型探针和任何突变探针杂交，则推断为利福平（RIF）耐药。在这项研究中，我们试图通过 rpoB 基因测序鉴定分枝杆菌分离株（n=203）中的这种“推断”突变，并确定它们与表型耐药性的关系。D516Y、H526N 和 L511P 突变与表型敏感（59%，n=38/64）和耐药（23.7%，n=33/139）抗菌药物敏感性试验（AST）结果均相关，而 S531W 突变仅与利福平耐药分离株（33%，n=33/139）相关。这些结果表明，在标准药物浓度下，一些“推断”突变可能会被 RIF-AST（表型敏感）漏检。LPA 的使用可以识别这些利福平耐药分离株，并且可以通过添加额外的突变探针（例如 S531W）来进一步提高 LPA 的特异性。需要进一步的研究来确定“推断”突变类型与临床/治疗结果的关系。
