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目的 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)的变异与其耐氟喹诺酮类 (FQNL)的关系。方法 采用琼脂平板双倍稀释法测定环丙沙星、左氧氟沙星、依诺沙星和诺氟沙星对临床分离的 31株肺炎克雷伯菌及其标准菌株ATCC 10 0 31的最低抑菌浓度 (MIC) ,并对此 32株菌GyrA的基因 (gyrA)和ParC的基因 (parC)进行PCR扩增和DNA序列的分析比较。结果 19株耐FQNL菌都存在GyrA变异 ,同FQNL耐药性相关的变异有Ser83(TCC)→Phe(TTC)、Ile(ATC)、Tyr(TAC)和Lys(TGC) ;Asp87(GAC)→Ala(GCC)。其中Ser83→Ile、Lys的变异是新发现。在 9株高度耐FQNL和 1株低度耐FQNL菌中同时存在ParC的变异 ,同FQNL耐药性相关的变异有丝氨酸Ser80 (AGC)→Ile(ATC)。ATCC 10 0 31的ParC同大肠埃希菌的ParC具有很好的同源性。结论 在耐FQNL肺炎克雷伯菌中普遍存在着GyrA的变异 ,其中以Ser83的变异多见。当细菌有GyrA的变异 ,同时合并有ParC的变异时 ,其耐药性往往会增强。
Objective To study the relationship between mutations of Klebsiella pneumoniae DNA gyrase A subunit (GyrA) and topoisomerase Ⅳ C subunit (ParC) and their resistance to fluoroquinolones (FQNL). Methods The antibacterial activity of ciprofloxacin, levofloxacin, enoxacin and norfloxacin against 31 Klebsiella pneumoniae isolates and their standard strains ATCC 1031 MIC). The gyrA gene and parC gene (parC) of 32 strains of bacteria were amplified by PCR and analyzed by DNA sequence. Results There were GyrA mutations in 19 strains of FQNL-resistant bacteria, and Ser83 (TCC) → Phe (TTC), Ile (ATC), Tyr (TAC) and Lys (TGC) Ala (GCC). The mutation of Ser83 → Ile and Lys is a new discovery. Variation of ParC was present in 9 highly resistant FQNL and 1 low resistant FQNL strains, with serine Ser80 (AGC) → Ile (ATC) related to FQNL resistance. ParC of ATCC1031 has good homology to ParC of Escherichia coli. Conclusion The mutation of GyrA is common in Klebsiella pneumoniae resistant to FQNL, of which Ser83 is more common. When bacteria have the mutation of GyrA, combined with the mutation of ParC, its resistance will often be enhanced.