Biological and Medical Informatics Research Center, San Diego State University, San Diego, California, USA.
Department of Medicine, University of California, San Diego, California, USA.
Sci Rep. 2017 Jun 19;7(1):3790. doi: 10.1038/s41598-017-03452-y.
Pyrazinamide (PZA) is an important first-line drug in all existing and new tuberculosis (TB) treatment regimens. PZA-resistance in M. tuberculosis is increasing, especially among M/XDR cases. Noted issues with PZA Drug Susceptibility Testing (DST) have driven the search for alternative tests. This study provides a comprehensive assessment of PZA molecular diagnostics in M/XDR TB cases. A set of 296, mostly XDR, clinical M. tuberculosis isolates from four countries were subjected to DST for eight drugs, confirmatory Wayne's assay, and whole-genome sequencing. Three genes implicated in PZA resistance, pncA, rpsA, and panD were investigated. Assuming all non-synonymous mutations cause resistance, we report 90% sensitivity and 65% specificity for a pncA-based molecular test. The addition of rpsA and panD potentially provides 2% increase in sensitivity. Molecular heterogeneity in pncA was associated with resistance and should be evaluated as a diagnostic tool. Mutations near the N-terminus and C-terminus of PZase were associated with East-Asian and Euro-American lineages, respectively. Finally, Euro-American isolates are most likely to have a wild-type PZase and escape molecular detection. Overall, the 8-10% resistance without markers may point to alternative mechanisms of resistance. Confirmatory mutagenesis may improve the disconcertingly low specificity but reduce sensitivity since not all mutations may cause resistance.
吡嗪酰胺（PZA）是所有现有和新的结核病（TB）治疗方案中的重要一线药物。结核分枝杆菌中的 PZA 耐药性正在增加，尤其是在 M/XDR 病例中。由于 PZA 药敏试验（DST）存在问题，人们一直在寻找替代试验。本研究对 M/XDR-TB 病例中的 PZA 分子诊断进行了全面评估。从四个国家收集了一组 296 株，主要是 XDR，临床分离的结核分枝杆菌，对 8 种药物进行了 DST、确认性韦恩测定和全基因组测序。研究了与 PZA 耐药性相关的三个基因，即 pncA、rpsA 和 panD。假设所有非同义突变都导致耐药性，我们报告了基于 pncA 的分子检测的 90%敏感性和 65%特异性。添加 rpsA 和 panD 可能会提高 2%的敏感性。pncA 中的分子异质性与耐药性相关，应作为诊断工具进行评估。靠近 PZase N 端和 C 端的突变与东亚和欧美谱系分别相关。最后，欧美分离株最有可能具有野生型 PZase 并逃避分子检测。总体而言，8-10%无标志物的耐药性可能表明存在其他耐药机制。确认性诱变可能会提高令人不安的低特异性，但会降低敏感性，因为并非所有突变都可能导致耐药性。
