【摘要】 建立人离体肠道模拟模型,研究微量环丙沙星对人源肠道大肠杆菌和粪肠球菌敏感性的影响,进而用聚合酶链反应法扩增耐药菌的gyrA基因的耐药决定区,并分析其耐药机制。结果显示,大肠杆菌连续培养后存活菌株对微量环丙沙星耐药,此耐药菌对其他抗菌药敏感;粪肠球菌经连续培养,对环丙沙星和其他抗菌药物仍敏感;耐药大肠杆菌的gyrA基因发生突变,248位碱基由C变为T,259位由G变为T,相应地,该基因编码的蛋白质在83位的丝氨酸和87位的天冬氨酸分别改变为亮氨酸和酪氨酸。研究表明,微量环丙沙星对人肠道菌群具有不同的选择作用,能诱导大肠杆菌产生耐药性。这为动物源食品中环丙沙星残留的安全性评价提供了试验依据。更多还原

【Abstract】 An in vitro gut simulation model has been developed to study the effects of low doses of ciprofloxacin on human Escherichia coli and Enterococcus faecalis.The ciprofloxacin-resistance-determining regions(QRDR) of gyrA in the ciprofloxacin-resistant bacteria were amplified by polymerase chain reaction in order to study the mechanism of antibiotic resistance.The result showed that Escherichia coli could produce antibiotic resistance to ciprofloxacin,but not to other antibiotics.Enterococcus faecalis did not produce antibiotic resistance to all antibiotics.Those ciprofloxacin-resistant Escherichia coli strains had double mutations of C-to-T transition at position 248(Ser 83 to Leu) and G-to-T transition at position 259(Asp 87 to Tyr).The study demonstrated that low concentration of ciprofloxacin had selective pressure on human intestinal flora and could induce Escherichia coli to produce antibiotic resistance.It supplies the data for safety assessment on ciprofloxacin residues in foods of animal origin.更多还原