【作者】 梁蓓蓓； 王睿； 柴栋；

【Author】 LIANG Bei-bei, Wang Rui, CHAI Dong. Department of Clinical Pharmacology, General Hospital of PLA, Beijing 100853, China

【机构】 解放军总医院临床药理药学研究室；

【摘要】 目的: 研究不同药物浓度、不同化学结构的氟喹诺酮类药物对突变选择窗(MSW)内筛选的大肠埃希菌耐药突变体的靶位耐药基因的影响。方法应用5种氟喹诺酮类药物在突变选择窗内(2MIC-MPC浓度的平板上)接种约1010菌量的 ATCC25922筛选第一步耐药突变体;采用琼脂平板二倍稀释法测定ATCC25922和耐药突变体的MIC;应用PCR以及DNA 测序方法确定ATCC25922和耐药突变体耐药决定簇QRDRs的gyrA、parC的突变位点和相应的氨基酸变化。结果 ATCC25922在MSW中共筛选53株第一步耐药突变体,所有的第一步突变体均为gyrA位点突变,无parC位点突变,其中有 79%(42株)为Ser-83→Leu位点突变,19％(10株)为Asp-87→Asn,20%(1株)为Gly81→Cys位点突变,83位和87 位为大肠埃希菌的常见突变位点。氟喹诺酮对Ser-83→Leu突变体的MIC较Gly81→Cys突变体的MIC高2～8倍,较 Asp-87→Asn突变体的MIC高1～2倍,Ser-83→Leu突变对细菌的敏感性影响最大,提示Ser-83→Leu是所有的突变位点中对耐药影响最重要的位点。结论氟喹诺酮对大肠埃希菌的主要靶位是GyrA,83位和87位突变为大肠埃希菌最常见突变位点。更多还原

【Abstract】 OBJECTIVE To investigate the effect of drug concentration、 drug structure of fluoroquinolones on the resistant gene of Escherichia coli mutants selected in the mutant selection window(MSW). METHODS The target genes, gyrA and parC of Escherichia coli mutants selected in the MSW were obtained by PCR method and sequenced by DMA sequencing. The agar dilution method was carried out to determine minimal inhibition concentration(MIC) of Escherichia coli mutants. RESULTS Among 53 mutants selected by five fluoroquinolones, 79% had a mutation from Ser to a Leu residue at position 83( a Ser-83-Leu mutation) detected in the quinolone resistant-determining region of the gyrA gene, 19% had a mutation from Asp to a Asn residue at position 87( a Asp-87Asn mutation), 2% was a mutation from Gly to a Cys residue at position 81( a Gly81-Cys mutation), and no parC mutation was detectable. MIC of mutation at position 83 was 2-8 fold larger than that of mutation at position 81 and 1-2 fold larger than that of mutation at position 87. Mutation at position 83 was the most important factor to influence the sensitivity of Escherichia coli. DNA gyrase is the primary target, mutation at position 83 and 87 was the most frequent and no-target mutation was also involved in the resistance. CONCLUSION DNA gyrase is the primary target of fluoroquinolone against E.coli, mutation at position 83 and 87 is the most frequent.更多还原