【摘要】 目的了解3种氟喹诺酮类(FQS)体外诱导肺炎克雷伯菌(Klebsiella pneumoniae,Kpn)耐药性的差异,研究肺炎克雷伯菌DNA旋转酶A亚单位(GyrA)和拓扑异构酶ⅣC亚基(ParC)的变异与其耐喹诺酮类药物的关系。方法采用环丙沙星(CIP)、左氧氟沙星(LEX)和加替沙星(GAT)对从临床分离8株Kpn进行体外分步诱导,采用琼脂平板二倍稀释法测定CIP、LVF及GAT对Kpn诱导前、后的最低抑菌浓度(MIC),并对诱导成功的17株Kpn的GyrA的基因(gyrA)和ParC的基因(parC)进行PCR扩增,选取其中8株Kpn DNA测序并进行序列分析比较。结果8株耐FQS菌株都存在GyrA变异,同FQS耐药性相关的变异有Ser83(TCC)→Phe(TTC)、Ile(ATC)和Tyr(TAC),Asp87(GAC)→Ala(GCC)、Ala(GCC)和Glu(GAA),5株Kpn同时存在ParC的变异:丝氨酸Ser80(AGC)→Ile(ATC)。结论本研究体外实验证实了Kpn可在长期低剂量的接触抗菌药物后形成耐药菌株。在高度耐FQS的Kpn中同时存在GyrA和ParC变异。更多还原

【Abstract】 Objective To understand the difference of drug resistance in Klebsiella pneumoniae induced by fluoroquinolones in vitro.To study the relation between the alterations in the DNA gyrase subunit A(GyrA),topoisomerase Ⅳsubunit C(ParC) and fluoroquinolones resistance in Klebsiella pneumoniae.Method 8 strains of Klebsiella pneumoniae isolated from clinical were multiple-step induced resistant strains in vitro with Ciprofloxacin,Levofloxacin and Gatifloxacin.The agar dilution method was carried out to determine minimal inhibition concentration(MIC) of Klebsiella pneumoniae before and after inducement.The genes of GyrA(gyrA) and ParC(parC) in induced resistant 17 strains were amplified by polymerase chain reaction(PCR).Their PCR products were purified and directly sequenced.Their DNA sequences were compared.Result The alterations in GyrA existed generally in 8 strains of Klebsiella pneumoniae resistant to FQS.In this study,the alterations related to FQS resistance included Ser83(TCC) → Phe(TTC),Ile(ATC) and Tyr(TAC),Asp87(GAC) →Gly(GGC),Ala(GCC) and Glu(GAA).Alteration in ParC existed in 5 strains of Klebsiella pneumoniae resistant to FQS at the same time and the alteration related to FQS resistance was Ser80(AGC)→ Ile(ATC).Conclusion The results of in vitro experiments on Klebsiella pneumoniae strains for induced resistance to some antibacterial agents.It shows that acquired resistance could be occurred when exposuring them to low level of some antibacterial agents for long term.The mutation of gyrA and parC gene exist simultaneously in the strains of Klebsiella pneumoniae resistant to FQS.更多还原