台灣分離之多重抗藥性結核桿菌rpoB基因分析

Analysis of rpoB Gene of Multidrug-resistant Tuberculosis Strains Isolated in Taiwan

多重抗藥性結核桿菌(Multidrug-resistant Tuberculosis ， MDR-TB) 對isoniazid(INH) 與rifampin(RMP)具有抗藥性。台灣2012年MDR-TB感染之個案有140人，佔已通報16,688個案人數的0.84%。isoniazid抗藥性之產生主要與katG和inhA基因的突變有關，而rifampin之抗藥性則是因為rpoB基因突變所導致。為了解MDR-TB的rpoB基因突變趨勢，針對本院所分離出來的MDR-TB菌株，利用DNA定序分析統計包含rpoB基因上codons 507~533熱點區(hot spot region)的上下游區域核酸 1366-1772片段，其突變的類型與比例，希望能找出感染MDR-TB的病人的臨床用藥的分子診斷輔助原則。從84位病人身上分離90株MDR-TB菌株，並分析rpoB基因突變，結果發現codon 531的突變佔62.2%，其次是codon 526佔12.2%，而codon 516佔11.1%，其他少量突變零星地散布在codons 490~584，則佔13.2%，以及少數序列缺失2.2%或無突變6.7%。分析MDR-TB codon 531突變後的二線抗藥性，可分成codon 531突變與無codon 531突變兩群，codon 531突變菌株的二線抗藥性比例比無codon 531突變的菌株抗藥性強約1~2倍，而且rifabutin抗性高達100%，而無codon 531突變的菌株對於rifabutin抗藥性也高達55.9%。以上的統計結果希望可以提供醫師對於治療MDR-TB病人時對於rifabutin用藥的參考。

Multidrug-resistant Tuberculosis (MDRTB) show resistance to isoniazid(INH) and rifampin (RMP). In Taiwan, a total of 140 patients were reported to be infected by MDRTB, which occupies 0.84% among the 16,688 infected cases in 2012.Generally the rifampin resistance is mainly due to rpoB mutations. To characterize the drug resistance pattern of ropB, in this study, we collected 90 isolates from 84 patients, and sequenced the nucleotide 1366-1772 including 81 nucleotides hot spot region codons 507~533. Results indicated codon 531 mutation occupies 62.2%,followed by codon 526 (12.2%),and 516(11.1%). Others contain scattered mutations among codons 490~584 (13.2%), deletion (2.2%) or no mutation (6.7%).Further studies indicated that codon 531 mutated strains showed increased second-line antibiotics resistance up to 1-2 fold, in contrast to those without mutations. Further, these strains are all rifabutin resistance (100%). By contrast, the codon 531 non-mutation strains showed 55.9% rifabutin resistance. Together, these data presented are helpful for clinical treatment of Mycobacterium tuberculosis infections.