中文摘要：

目的：探讨真菌密度感应分子 Farnesol 在表皮葡萄球菌和白假丝酵母菌混合生物膜形成中的作用。方法将表皮葡萄球菌标准株 ATCC35984及白假丝酵母菌标准株 ATCC10231混合培养建立体外生物膜模型,加入 Farnesol或不加入 Farnesol 分为 Farnesol 处理组和对照组,孵育2、4、6、8、12、24、48、72、96 h 时用结晶紫染色法半定量检测生物膜形成能力；二甲氧唑黄（XTT）比色法评价生物膜的体外生长动力学；扫描电子显微镜观察生物膜超微结构；荧光定量 PCR 分析各组生物膜形成相关基因的表达情况。结果结晶紫染色法生物膜半定量检测显示,12、24 h Farnesol处理组和对照组差异有统计学意义（P ＜0.05）。XTT 比色法生长动力学检测显示,Farnesol 处理组在4、48 h 与对照组比较,差异有统计学意义（P ＜0.05）。扫描电镜结果显示,对照组混合生物膜结构较 Farnesol 处理组致密复杂。荧光定量 PCR 结果显示,培养6h Farnesol 处理组表皮葡萄球菌生物膜形成相关基因 icaA、fbe、aap 基因及白假丝酵母菌生物膜形成相关基因 als3、hwp1、efg1基因的表达下调；培养24 h Farnesol 处理组表皮葡萄球菌生物膜形成相关基因 aap 基因及白假丝酵母菌生物膜形成相关基因 als3、hwp1、efg1基 因 的 表 达 下 调。结论在真菌密度感应分子Farnesol 的干预下,对照组形成的混合生物膜较 Farnesol 处理组结构更为致密及复杂,这种结构的改变可能与 Farne-sol 处理组白假丝酵母菌生物膜形成相关基因 als3、hwp1、efg1基因的表达下调相关性更密切。

英文摘要：

Objective To explore the function of Farnesol in the formation of Staphylococcus epidermidis- Candida albicans mixed species biofilms. Methods The strains of Staphylococcus epidermidis ATCC35984 and Candida albicans ATCC10231 were co-cultured to form mixed species of biofilms. Then they were divided into Farnesol group and control group based on treatment with Farnesol or not. Biofilm mass was semi-quantified by crystal violet semi-quantitative adherence assay at 2, 4, 6, 8, 12, 24, 48, 72 and 96 h of incubation. XTT assay was performed to determine the growth kinetics at the same time. Scanning electron microscopy was used to observe the ultrastructure of the biofilms. Real-time PCR was used to analyze the expressions of icaA, fbe, aap, hwpl, als3 and efgl genes. Results Crystal violet semi-quantitative adherence assay showed that at 12 and 24 h of incubation, Farnesol group had significantly decreased optical density compared to control group （P~O. 05）. XTT assay showed that at 4 and 48 h of incubation, biofilms growth kinetics differed significantly in Farnesol group and control group （P~0.05）. Scanning electron microscopy showed that the three-dimensional structure of mix-biofilm in control group was more complex. As real-time PCR showed, after 6-hour culture, the expressions of icaA, fbe, aap, hwpl, als3 and efgl genes in Farnesol group were down-regulated compared to those in control group and after 24-hour culture the expressions of aap, hwpl, als3 and efgl genes in Farnesol group were down-regulated compared to those in control group. Oonclusion With the intervention by fungal quorum sensing molecules Farnesol, the structure in control group became denser and more complex than that in Farnesol group. This change may have a closer correlation with the down-regulated expressions of als3, hwpl and efgl genes, which are related to the formation of Candida albicans biofilms.