Objective:To explore the effects of sub-inhibitory concentration of levofloxacin on ex-pression of virulence genes and virulence regulatory genes of MRSA strains,and to provide experimental basis and idea for reasonable guiding quilones usage in treatment of multi-drug resistant bacteria infec-tion.Methods:Five methicillin resistant resistant Staphylococcus aureus clinical isolates were used as subjects,which were cultured with 1.6μg/mL( MIC1/10) and 8μg/mL( MIC1/2) concentration of levoflox-acin for 6 hours. Then,scanning electron microscopy technique was used to observe the morphological changes of MRSA strains in different groups,and real-time flurorescent quantitative PCR technique was employed to detect the expression levels of virulence genes and virulence regulatory genes,including fi-bronectin A(fnbA),α-hemolysin(hla),leukocidin D(luk-D),E(luk-E),staphylococcal protein A (spa)and enterotoxinA.Results:At 6 hours of co-culture,Staphylococcus aureus showed tatterring and splitting at different degrees for 1.6μg/mL(MIC1/10)and 8μg/mL(MIC1/2)levofloxacin groups.Compa- ring with control group,the mRNA expression levels of spa,hla,luk-D and luk-E of MRSA strains in the above two experimental groups were significantly higher( P＜0.01) ,and the mRNA expression of spa and sea was not detected. Conclusion:Sub-inhibitory concentration of levofloxacin shows bactericidal activity at some degree,and can significantly suppress the expression of multiple virulence genes and virulence regulatory genes.%目的:探究亚抑菌浓度左氧氟沙星对甲氧西林耐药金黄色葡萄球菌临床株毒力基因表达的影响效应,为更合理使用喹诺酮类抗生素治疗多重耐药细菌感染提供新的实验依据和思路.方法:以5株甲氧西林耐药金黄色葡萄球菌临床分离株为研究对象,采用1.6μg/mL(MIC1/10)、8μg/mL(MIC1/2)亚抑菌浓度左氧氟沙星与其体外共培养6h,采用扫描电镜技术观察不同组金黄色葡萄球菌形态特征变化,采用荧光定量PCR方法检测各组MRSA株毒力基因(纤维黏连蛋白A、葡萄球菌蛋白A、α溶血素、杀白细胞毒素D和E) mRNA表达水平的变化.结果:体外共培养6 h时,1.6μg/mL(MIC1/10)、8μg/mL(MIC1/2)亚抑菌浓度左氧氟沙星MRSA组菌体均出现不同程度破碎和裂解,其毒力基因( spa、hla、luk-D和luk-E) mRNA表达水平均明显低于对照组( P＜0.01),fnbA和sea 2个毒力基因在培养6 h时未能检测到其表达.结论:亚抑菌浓度左氧氟沙星对MRSA临床株仍具有一定杀伤活性,且可显著抑制MRSA多种毒力基因的表达.
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