中文摘要：

探讨柴胡皂苷a对金黄色葡萄球菌的抑菌活性,确定亚抑菌浓度的柴胡皂苷a对金黄色葡萄球菌基因转录表达谱的影响。按NCCLS推荐的试管肉汤倍比稀释法测定柴胡皂苷a对32株临床分离的金黄色葡萄球菌和标准菌株ATCC25923的最小抑菌浓度（MICs）,绘制标准菌株ATCC25923的生长曲线,用定制的Affymetrix基因芯片检测1/2×MIC（4mg.L-1）柴胡皂苷a对标准菌株ATCC25923基因表达谱的影响。结果表明,柴胡皂苷a对33株金黄色葡萄球菌的MICs为1～32mg.L-1;基因表达谱分析有26个上调基因,68个下调基因,其中1个编码超氧负离子压力反应蛋白基因被大幅度地上调,13个毒力基因被诱导,并且都被抑制;这表明柴胡皂苷a对32株临床分离的金黄色葡萄球菌及标准菌株都有抑菌活性。基因芯片分析表明,柴胡皂苷a的抗菌作用能够同时影响金黄色葡萄球菌不同的途径基因。

英文摘要：

To investigate the inhibitory activity of saikosaponin-a against S.aureus and determine the global transcription pattern of S.aureus in response to subinhibitory concentrations of saikosaponin-a,the minimum inhibition concentrations （MICs） of saikosaponin-a against 32 clinical S.aureus isolates and the standard strain ATCC25923 were tested.Growth curve for S.aureus strain ATCC25923 was performed.Custom-made Affymetrix GeneChipsTM were used to determine the global transcriptional response of S.aureus ATCC25923 triggered by saikosaponin-a at concentration of 1/2×MIC（4 mg·L-1）.The rsults showed that MICs of saikosaponin-a against 33 S.aureus strains ranged from 1 to 32 mg·L-1.26 genes were identified to be upregulated and 68 genes were downregulated upon exposure to saikosaponin-a.Of these,1 gene coding involved in superoxide radicals general stress protein was differentially up-regulated by saikosaponin-a,13 virulence genes were induced and inhibited in response to saikosaponin-a.Saikosaponin-a showed antimicrobial activities against all tested strains of S.aureus.GeneChip analysis demonstrated that saikosaponin-a may affect different pathway genes S.aureus simultaneously.