结核分枝杆菌DNA促旋酶基因突变与耐氟喹诺酮类药物的相关性研究

目的 分析MDR TB结核分枝杆菌临床分离株的DNA促旋酶（gyr）基因突变特点,初步探究MDR-TB对氟喹诺酮类药物耐药与gyr基因突变的相关性.方法 采用最低抑菌浓度（MIC）法筛选MDR-TB,对17株临床MDRTB菌株应用DNA直接测序法检测gyr基因的突变情况,分析细菌基因突变与耐药产生的相关性.结果 Mtb 1株标准菌株（H37Rv）未见gyr A亚单位基因（gyrA）和gyr B亚单位基因（gyrB）基因突变,所有17株临床菌株gyrA均存在95位AGC→ACC.12株耐环丙沙星和左氧氟沙星菌株中,10株gyrA产生了错义突变,突变率为83.3％;突变位点位于89位、90位、91位和94位;1株发生了gyrB突变,突变位点位于500位.耐莫西沙星的9株耐药株中,8株gyrA发生突变,占88.9％.结论 gyrA基因突变是Mtb对氟喹诺酮类药物产生耐药的机制之一;gyrA的错义突变主要发生在第89位、90位、91位、94位密码子上.

Correlation between the mutations of gyrase gene and fluoroquinolone resistance in Mycobacterium tuberculosis

Objective To analyze the mutations of gyrase （gyr） gene in multidrug resistant （MDR） M.tuberculosis clinical isolates,and to investigate the correlation between the gyr mutations and fluoroquinolone （FQ） resistance.Methods Seventeen MDR M.tuberculosis isolates were analyzed the FQ resistance using minimum inhibitory concentration （MIC） method,and detected gyr mutations by DNA sequencing.Results No mutation was observed in gyrA and gyrB genes of M.tuberculosis H37Rv,while 17 clinical MDR isolates all carried the substitution AGC→ACC at codon 95.Among 12 FQ-resistant isolates,10 （83.3％） harbored missense mutation in gyrA gene,including codon 89,90,91 and 94.In addition,1 isolate had mutation at codon 500 of gyrB gene.Among 9 moxifloxacin-resistant isolates,8 （88.9％） showed the mutations in gyrA gene.Conclusion The mutation in gyrA is one of the most important mechanism for FQ resistance in M.tuberculosis.The most frequent mutations located at codon 89,90,91 and 94.