中文摘要：

【目的】探讨从养殖场动物、环境和饲养员分离的大肠杆菌的gyrA和paTC基因突变特征。【方法】用琼脂稀释法测定环丙沙星和恩诺沙星对菌株的最小抑菌浓度。PCR扩增gyTA和parC基因的喹诺酮耐药决定区，扩增的片段长度分别为525bp和487bp，PCR产物直接测序。【结果】在63株突变株中，在GyrA亚基发生的氨基酸替代有Ser83→Leu（62株）和Asp87→Asn（52株）、Asp87→Tyr（2株）、Asp87→HiS（2株）；ParC亚基的氨基酸替代有Ser80→Ile（47株）、Ser80→Arg（2株）和Glu84→Val（3株）、Glu84→Lys（4株）、Glu84→G1y（5株）、Glu84→Ala（1株）。环丙沙星对菌株的MIC小于0．125μg·ml^-1时，gyrA和ParC亚基均没有任何变异；环丙沙星的MIC为0．125～0．25μg·ml^-1时，GyrA亚基出现单一氨基酸替代；环丙沙星的MIC为0．5～32μg·ml^-1时，出现GyrA83位和87位双替代或者GyrA83和ParC80位双替代；环丙沙星的MIC为4～128μg·ml^-1，发生GyrA双替代和ParC单替代；环丙沙星的）dIC在16～128μg·ml^-1，发生GyrA双替代和ParC双替代。【结论】不同来源的耐氟喹诺酮类药物的大肠杆菌GyrA和ParC具有多种氨基酸替代类型，而且GyrA和ParC突变位点的数量与菌株对氟喹诺酮类耐药水平呈正相关。

英文摘要：

[ Objective ] To detect mutations ofgyrA and parC in 72 Escherichia coli strains isolated from human feces, animal feces and the environment. [Method] MICs of ciprofloxacin or enrofloxacin for 72 isolates were determined by an agar dilution test with standard strain ATCC25922 as the control. The mutations in the quinolone resistance-determining regions （QRDRs） of the gyrA andparC genes were analyzed by PCR and sequencing. [Result] Amino acid substitutions （number of strains） found in 63 mutants were Ser83→Leu （62） and Asp87vAsn （52） , Asp87→Tyr （2） , Asp87→His （2） in GyrA and Ser80→Ile （47） , Ser80→Arg （2） and Glu84→Val （3） , Glu84→Lys （4） , Glu84→Gly （5） , Glu84→Ala （ 1 ） in ParC. No amino acid changes in GyrA or ParC were detected when strains MIC of ciprofloxacin were under 0.125 μg·ml^-1. A single substitution in GyrA was found in the strains whose MIC ofciprofloxacin ranged from 0.125 to 0.251μg·ml^-1. Double substitutions in GyrA or one in GyrA with one in ParC were found in the strains with MICof ciprofloxacin ranging from 0.5 to 32 μg·ml^-1. A double changes in GyrA and a single change in ParC were found in strains with MIC ofciprofloxacin ranging from 4 to 128μg·ml^-1. Double changes in GyrA and double changes in ParC were found in strains with MIC of ciprofloxacin ranging from 16 to 128μg·ml^-1. [Conclusion] A variety of amino acid changes in GyrA and ParC were detected in the fluoroquinolone-resistant E. coli isolates from different origin. A correlation was found between the number of changes in the QRDR of GyrA and ParC and the resistance level to fluoroquinolone in E. coli strains.