莫西沙星与左氧氟沙星对结核分枝杆菌的交叉耐药性研究

Study on the cross-resistance of moxifloxacin and levofloxacin in Mycobacterium tuberculosis

目的探讨莫西沙星(MXF)与左氧氟沙星(LVF)对结核分枝杆菌的交叉耐药性及耐药基因突变位点,为临床用药提供理论依据。方法选取结核分枝杆菌标准株H37Rv和73株左氧氟沙星耐药的耐多药结核分枝杆菌(MDR-TB)临床分离株以及5株对左氟沙星敏感的MDR-TB临床分离株,以试管二倍稀释法采用7H9培养基,测定以上菌株对MXF和LVF的MIC;通过直接测序法测定gyrA基因喹诺酮类药物耐药决定区(QRDR)320 bp的基因突变位点。结果MXF的MIC比LVF低4～8倍;H37Rv未发生gyrA基因突变;78株MDR-TB临床分离株均有Ser95Thr突变;73株LVF耐药的MDR-TB菌株中,35株(47.94%)对LVF低耐药(MIC为1～8μg/ml)的菌株和31株(42.46%)对LVF高耐药株中,除4株只有Ser95Thr突变外,其他菌株同时有Ala90Val、Asp94His、Asp94Asn、Asp94Gly、Asp94Ala、Asp94Tyr突变。结论莫西沙星较左氧氟沙星的抗结核活性强4～8倍,为不完全交叉耐药;gyrA基因90位和94位突变与MDR-TB菌株对LVF、MXF耐药有关,低耐药与高耐药的突变氨基酸种类有差别,有望将测序作为临床左氟沙星分子药敏试验方法。

Objective To investigating the cross resistance of moxifloxacin and levofloxacin in M. tuberculosis, gene mutations of quinolone-resistant isolates to provide a theoretical basis for clinical treatment. Methods M. tuberculosis strain HavRv and 78 multidrug-resistant M. tuberculosis clinical isolates （73 LVF-resistant and 5 LVF-sensitive） were studied. The MICs of these isolates to moxifloxacin and levofloxacin were determined by the tube doubling dilution method on 7H9 media. The quinolone resistance-determining region （QRDR） mutations of gyrA genes from M. tuberculosis isolates were detected with DNA sequencing. Results The MICs of MXF were lower 4 to 8 fold than that of LVF. The strain HaTRv wasn＇t found any gyrA gene mutation. 78 MDR-TB isolates have Ser95Thr gyrA mutations. Of 73 MDR-TB isolates with LVF resistance, 35（47.94%） were low-resistant to LVF （MICs 1 to 8μg/ml）, al （42.46%）were high-resistant to LVF. Four isolates have only gyrA Ser95Thr mutation, the other isolates had combinative gene mutations as follow： Ala90Val, Asp94His, Asp94Asn, Asp94Gly, Asp94Ala, and Asp94Tyr. Conclusions The MXF and LVF presented a incomplete cross-resistance. The mutation of gyrA gene correlates with the LVF and MXF resistances in M. tuberculosis.