探针熔解分析法检测结核分枝杆菌异烟肼耐药突变的应用和评价

目的 评价PMA技术检测MTB对INH耐药突变的价值,调查INH耐药突变发生特征.方法 MTB标准株H37Rv来自国家结核病参比实验室,1株INH敏感株和1株katG S315TACC突变株来自厦门市疾病预防控制中心,7株含有已知INH耐药突变的结核耐药株来自深圳慢性病防治中心、河南省疾病预防控制中心、中国人民解放军第309医院和厦门市疾病预防控制中心.707份MTB临床分离株来自厦门市疾病预防控制中心、厦门市第一医院和漳州市疾病预防控制中心,126份MTB涂阳痰标本来自厦门市同安区疾病预防控制中心.MTB标准株H37Rv、7株MTB INH耐药株和833份临床标本均采用厦门致善结核分枝杆菌异烟肼耐药突变检测试剂盒热裂解法提取基因组DNA,1株INH敏感株和1株katG S315T ACC突变株采用AxyPrepTM细菌基因组DNA提取试剂盒提取基因组DNA.熔解曲线分析所检标本与野生型对照在katG315位密码子、inhA启动子区(- 17～-8位点)、ahpC启动子区(-44～-30以及-15 ～3位点)及inhA94位密码子的熔解温度(Tm值)差异判断标本是否发生INH耐药突变.3×105拷贝/反应的野生株和katG S315T ACC突变株以10倍梯度稀释至300拷贝/反应,分析PMA技术的灵敏度.用PMA技术检测7株含有已知INH耐药突变的结核耐药株,评价特异性,并就其中5种耐药突变进行重复性检验.测序验证PMA技术对833份标本INH耐药性的临床检测效能.结果 PMA技术从核酸提取到结果判断可在3小时内完成,在标准96孔实时PCR仪器上可同时检测46份标本.对野生株和katG S315T ACC突变株的灵敏度均为300拷贝/反应,能够同时区分9种INH耐药相关点突变或缺失,5种耐药突变的Tm值标准偏差均在0.5℃之内.检出的162份突变标本与测序验证结果均一致.临床标本验证突变率为19.4％( 162/833),在所检出的14种INH耐药突变katGS315T( AGC →ACC)、inhA启动子区- 15C→T和katG S315N (AGC→AAC)这3种突变占INH耐药突变标本的83.3％(135/162).结论 PMA技术可快速、灵敏、特异检测结核INH耐药突变.

Application and evaluation of a probe melting analysis-based assay for detection of Isoniazid-resistant mutations in Mycobacterium tuberculosis

Objective To validate the performance of a PMA-based assay for detection of INH-resistant mutations in MTB and investigate the mutation characteristic of INH-resistance.Methods The MTB standard strain H37Rv was from National Tuberculosis Reference Laboratory,1 wild-type strain and 1 katG S315T ACC mutant strain were from Xiamen CDC,7 MTB INH-resistant strains with known INH resistance mutations were from Shenzhen Center for Chronic Disease Control,Henan CDC,No.309 Hospital of PIA and Xiamen CDC.707 MTB clinical isolates were from Xiamen CDC,Xiamen No.1 Hospital and Zhangzhou CDC,126 sputum samples were from Xiamen Tongan CDC.The genomic DNA of the MTB standard strain H37Rv,7 MTB INH-resistant strains and 833 clinical samples,were extracted with Xiamen Zeesan Mycobacterium tuberculosis Isoniazid-resistance Mutation Test Kit using the thermal lysis method.The genomic DNA of 1 wild-type strain and 1 katG S315T ACC mutant strain were extracted with AxyPrep Bacterial Genomic DNA Miniprep Kit.The mutations were discriminated by the △Tm between the samples and wild type control in katG315 codon,inhA promoter -17 to -8 region,ahpC promoter region -44 to -30 and - 15 to 3,and inhA94 codon.A 10-fold dilution series of MTB DNA from 3 × 105 to 300 copies/ reaction obtained from a wild-type strain and a katG S315T ACC mutant strain,respectively,were prepared to determine the analytical sensitivity.Seven MTB INH-resistant strains with 9 predetermined mutations were used for the analytical specificity assay,and 5 mutants of which were used for the repeatability assay.The clinical detection performance of PMA assay were confirmed by the sequencing method in 833 samples.Results Results could be obtained within 3 hours from DNA extraction to PMA assay,including 46 samples in a standard 96-well real-time PCR instrument simultaneously.The analytical sensitivities of PMA were 300 copies/reaction for both the wild-type strain and katG S315T ACC mutant strain.Nine INH-resistant point mutations could be discriminated and 5 of which had standard deviations of melting temperature less than 0.5 ℃.Fully concordant results of mutant locus between PMA assay and sequencing were obtained in all 162 mutant samples.INH-resistant mutations in the four loci were found in 19.4％ (162/833) samples by PMA assay in Xiamen and Zhangzhou.Among the 14 lNH-resistant mutant types detected,katG S315T ( AGC→ACC),inhA promoter - 15C→T and katG S315N (AGC→AAC) accounted for 83.3％ (135/162) of the overall mutations.