摘要目的 调查我国肺炎链球菌对不同氟喹诺酮类抗生素(FQ)的耐药性,研究耐药突变位点与FQ耐药性的关系.方法 收集2010年6-12月我国9个城市12家教学医院临床分离的232株肺炎链球菌,用琼脂稀释法测定环丙沙星、左氧氟沙星和莫西沙星等16种抗菌药物的抗菌活性.选取左氧氟沙星MIC≥1 mg/L的菌株进行parC、parE和gyrA基因喹诺酮耐药决定区(QRDR)PCR扩增和序列分析.结果 环丙沙星、左氧氟沙星和莫西沙星的敏感度分别53.9％ (125/232)、98.7％ (229/232)和98.7％ (229/232).选取19株左氧氟沙星MIC≥2 mg/L的菌株并筛选出24株左氧氟沙星MIC值为1 mg/L的菌株,在选取的43株肺炎链球菌中,当parE靶点发生单一突变时,左氧氟沙星的MIC值为1～2 mg/L,环丙沙星的MIC值为2 mg/L,莫西沙星的MIC值为0.125～0.25 mg/L.当parE和parC靶点均有突变时,大部分菌株左氧氟沙星的MIC值为2 mg/L,环丙沙星的MIC值为4 mg/L,莫西沙星的MIC值为0.25 mg/L或0.50 mg/L.当parE和gyrA靶点同时突变时,左氧氟沙星的MIC值为16 mg/L,环丙沙星的MIC≥16 mg/L,莫西沙星的MIC值为4 mg/L.卡方检验结果发现,parE基因和parC基因双突变比parE基因单突变更能导致左氧氟沙星耐药性升高.结论 当parE/parC靶点产生突变时,左氧氟沙星和环丙沙星的MIC值已有升高,但莫西沙星MIC值还处于低水平;只有当parC/parE和gyrA双位点突变时,莫西沙星才达到耐药水平.

abstractsObjective To investigate the relationship between different fluoroquinolone (FQ) resistance of Streptococcus pneumoniae and the mutations of target genes.Methods A total of 232 Streptococcus pneumoniae isolates were collected from 12 teaching hospitals at 9 cities between June and December 2010.The antibacterial activities of 16 antimicrobial agents were determined by agar dilution method.The ciprofloxacin,levofloxacin and moxifloxacin MIC≥1 mg/L isolates were selected to detect the mutations in QRDR (parC,parE,and gyrA genes) through PCR combined sequencing.Results The susceptible rates of ciprofloxacin,levofloxacin and moxifloxacin were 53.9％ (125/232),98.7％ (229/232),98.7％ (229/232).Forty-three strains were randomly selected to be analyzed,including 19 levofloxacin MIC≥2 mg/L strains and 24 levofloxacin MIC =1 mg/L strains.The MIC of levofloxacin were 1-2 mg/L,ciprofloxacin were 2 mg/L and moxifloxacin were 0.125-0.250 mg/L when a single mutation in parE occurred.The MIC of levofloxacin were 2 rng/L,ciprofloxacin were 4 mg/L and moxifloxacin were 0.25 mg/L or 0.50 mg/L when mutations in both parE and parC occurred.The MIC of levofloxacin were 16 mg/ L,ciprofloxacin were ≥ 16 mg/L and moxifloxacin were 4 mg/L when mutations in both parE and gyrA occurred.Conclusion The single mutation in parE/parC is associated with low level levofloxacin and ciprofloxacin resistance,while double mutations in both parC/parE and gyrA are associated with moxifloxacin resistance.