慢性化脓性中耳炎中的肺炎克雷伯菌对氟喹诺酮类药物的耐药机制

目的 研究慢性化脓性中耳炎病例中分离肺炎克雷伯菌Ⅱ型拓扑异构酶基因突变与耐氟喹诺酮类药物的关系.方法 用二倍琼脂稀释法检测6种氟喹诺酮类药物对40株肺炎克雷伯菌临床分离株的最低抑菌浓度,PCR 扩增 gyrA、parC 基因的喹诺酮耐药决定区(QPDR),产物测序后分析.结果 有26株Ⅱ型拓扑异构酶基因发生突变,突变发...

Study of the mechanism of fluoroquinolone resistance in Klebsiella pneumoniae in chronic suppurative otitis media

Objective To study the correlation between gene mutation of type Ⅱ topoisomerase and fluoroquinolone resistance of Klebsiella pneumoniae isolated from chronic suppurative otitis media.Methods The MICs of 6 kinds of fluoroquinolones against Klebsiella pneumoniae isolated from 40 specimens of chronic suppurative otitis media were detected with the agar dilution method.The quinolone resistance determining regions of gyrA,parC genes were amplified by polymerase chain reaction（PCR） and sequenced.Results Gene mutation of type Ⅱtopoisomerases occurred in 26 isolates with gyrA（26 strains） and parC（13 strains）genes as major mutation sites.The mutations at position 83,87 in gyrA and 80 in parC leading to substitution of Serine by Tyrosine or Phenylalanine or Isoleucine were found frequently.Single mutation occurred in gyrA.The strains with both gyrA and parC mutations were four times more resistant than the strains which had only parC mutation.Conclusion The mutations of 83 and 87 condons of gyrA and the mutations of 80 and 84 condons of parC genes result in fluroquinolone resistance,and the mutations of 83 condon of gyrA gene are predominant.The low-level fluoroquinolone resistance strains are detected a single mutation in gyrA gene while high-level fluoroquinolone resistance are associated with simultaneous mutations in both GyrA and ParC.