肺炎链球菌临床分离株喹诺酮耐药决定区突变与左氧氟沙星敏感性下降相关性研究

Study on the correlation between the mutations in the quinolone-resistance- determining- region in streptococcus pneumoniae clinical isolates and the decline of thelevofloxacin's susceptivity

目的分析杭州市肺炎链球菌临床菌株parC/parE和gyrA/gyrB喹诺酮耐药决定区（QRDR）突变,及与喹诺酮类药物敏感性下降的相关性。方法采用琼脂稀释法检测37株临床菌株对8种抗生素的最小抑菌浓度（MIC）,PCR法扩增目的基因并测序。结果对左氧氟沙星、莫西沙星和万古霉素全部敏感,其余抗生素耐药率都〉60%,对左氧氟沙星MIC≤1 mg/L和MIC=2 mg/L分别有21株和16株。所有菌株gyrA/gyrB的均无突变,其中3株parC/parE也未见突变;34株临床菌株parE有突变,其中10株同时存在parC基因突变,parE基因分别有33株和8株发生I460V和D435N突变,parC基因有8株发生S79F突变。MIC=2 mg/L的菌株中parC/parE基因同时突变、S79F和/或D435N突变明显高于MIC≤1 mg/L菌株（χ2=4.2～6.2,P〈0.05）。结论本地区未发现左氧氟沙星耐药肺炎链球菌株,parC/parE同时突变、S79F和/或D435N突变使左氧氟沙星MIC提高。监测临床菌株parC/parE和gyrA/gyrB突变情况,防止药物诱导耐药株的产生。

Objective To analyze the correlation between the mutations in the quinolone - resistance - determining - region （QRDR） within genes ofparC/parE and gyrA/gyrB in streptococcus pneumoniae clinical isolates andthe decline of thelevofloxacin＇ s susceptivity in Hangzhou. Methods MICs of 8 antimierobials were determined by agar dilution method, PCR and DNA sequencing were conducted to analyze QRDR associated genes ofparC/parE and gyrA/gyrB in 37 isolates. Results All the isolates were susceptible to levofloxacin, moxifloxacin and vancomycin. The rest of antibiotic resistance rate were greater than 60% MIC ~〈 1 mg/L and MIC = 2 mg/L to levofloxacin were 21 and 16 isolates, respectively. All the isolates were no mutation of gyrA/gyrB genes, three of them were no mutation ofparC/parE genes. 34 isolates had mutations in pare gene, 10 of them had mutations in parC gene. 33 and 8 isolates had I460V and D435N mutations in parE gene, respectively. 8 isolates had S79F mutations in parC gene. Mutations in parC/parE genes at the same time,mutation of S79F and/or D435N in MIC =2 mg/L isolates were significantly higher than that MIC〈1 mg/L of isolates0（2 =4.2-6.2,P〈0.05）. Conclusion No isolate was found resistant to quinolones, The MIC of levofloxacin were improved wfien mutations in parC and parE, $79F and/or D435N occurred. Monitoring parC/parE said and gyrA/gyrB mutations of isolates situation in order to prevent the formation of resistant isolates led by the medicine.