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目的比较左氧氟沙星、莫西沙星和奈诺沙星对金黄色葡萄球菌的体外抗菌活性,初步探索金黄色葡萄球菌gyrA和parC基因突变对3种抗菌药物耐药性的影响及3种药物对金黄色葡萄球菌gyrA和parC基因的优先作用顺序。方法利用琼脂平板稀释法测定左氧氟沙星、莫西沙星和奈诺沙星分别对50株金黄色葡萄球菌的最低抑菌浓度(minimal inhibitory concentration,MIC);测定4株已知特定基因位点细菌(其中RN450为实验室菌株,已知基因序列,无任何位点突变)的MIC和防耐药突变浓度(mutant prevention concentration,MPC),在已知MIC和MPC基础上考察4株细菌的恢复生长细菌情况,对恢复生长细菌进行菌落计数并描记细菌恢复生长曲线。结果左氧氟沙星对50株金黄色葡萄球菌的MIC90(可抑制90%细菌生长的药物浓度)(16μg·m L~(-1))分别是莫西沙星(2μg·m L~(-1))和奈诺沙星(0.5μg·m L~(-1))的8倍和32倍。从细菌恢复曲线上来看,在相同药物浓度时,对于不同药物来说,奈诺沙星的恢复生长细菌比例最小,而左氧氟沙星的恢复生长细菌比例最大;对于不同位点突变的细菌来说,RN450的恢复生长比例最小,而RN450A3的恢复生长比例最大。结论 3种药物对金黄色葡萄球菌的体外抗菌活性强弱顺序为:奈诺沙星>莫西沙星>左氧氟沙星;相较于左氧氟沙星和莫西沙星,奈诺沙星可在较低浓度时抑制细菌生长,且对不同基因位点突变细菌均有强大抑制作用。左氧氟沙星可能优先作用于金黄色葡萄球菌的拓扑异构酶Ⅳ的parC基因,而莫西沙星和奈诺沙星则可能几乎同时作用于金黄色葡萄球菌DNA旋转酶的gyrA基因和拓扑异构酶Ⅳ的parC基因。
Objective To compare the in vitro antibacterial activity of levofloxacin, moxifloxacin and nelfoxacin against Staphylococcus aureus and explore the effects of gyrA and parC mutations of S. aureus on the resistance of three antimicrobial agents and the effect of three drugs against golden yellow Staphylococcus gyrA and parC genes are preferentially ordered. Methods Minimal inhibitory concentration (MIC) of levofloxacin, moxifloxacin and nanofloxacin against 50 Staphylococcus aureus were determined by agar plate dilution method. Four strains of bacteria with known specific gene loci RN450 was a laboratory strain with known gene sequence without any site mutation) and mutant prevention concentration (MPC). Based on the known MICs and MPCs, the bacterial growth recovery of the four strains was investigated , Count colonies of resumed germs and trace bacterial growth recovery curves. Results The MIC90 of levofloxacin against 50 strains of Staphylococcus aureus was 16 μg · mL -1 and 2 μg · m L -1 for moxifloxacin 8-fold and 32-fold higher than that of ninuofloxacin (0.5μg · m L -1). From the curve of bacterial recovery, in the same drug concentration, for different drugs, the proportion of the bacteria that restore the growth of ninuofloxacin is the smallest, and that of levofloxacin is the largest. For the bacteria with different sites mutation, RN450 Of the recovery growth of the smallest proportion, and RN450A3 the largest proportion of the restoration of growth. Conclusions The in vitro antibacterial activity of the three drugs against Staphylococcus aureus is in the following order: nefloxacin> moxifloxacin> levofloxacin. Compared with levofloxacin and moxifloxacin, nefloxacin can inhibit bacteria at lower concentration Growth, and mutation of different gene loci have a strong inhibitory effect on bacteria. Levofloxacin may preferentially act on the toC gene of topoisomerase IV of S. aureus while moxifloxacin and ninufloxacin may act almost simultaneously on the gyrA gene of Staphylococcus aureus DNA gyrase and the topoisomerase IV ParC gene.