Objective To determine the ability of biofilm formation of Staphylococcus ephtermidis isolates and analyze the correlation between the icaA gene and its expression and biofilm formation. Methods Collecting 205 Staphylococcus epidermidis isolates identified with normal laboratory tests (coagulase-negative, biochemical identification, polymyxin-resistant and novobiocin-sensitive ), the suspected isolates were con-formed with API-Staph. Biofilm production was assessed by incubating the strains on Congo Red Agar (CRA) plates and quantitative biofilm production determined by a 96-well tissue culture plate and biofilm morphous were detected by scanning electron microscope ( SEM ) ; Amplifying partial fragments of icaA genes with PCR; Analyzing the expression levels of icaA gene with RT-PCR through Bio-Rad system and Quantity One software. Results 24 isolates showed positive in CRA tests, 22 isolates were positive in semiquantita- tive adhesion assays and 28 isolates existed icaA gene among 205 isolates of Staphylococcus epidermidis. The icaA-positive strains demonstrated biofilm formation (microcolonies on silica films ) while icaA-negative strains only adhered as individual cells under scanning electron microscope. All 22 strains which showed positive in semiquantitative adhesion assays harbored the icaA gene. The expression levels of icaA gene with RT-PCR in 6 Staphylococcus epidermidis isolates showed a higher tendency in 4 strains which demonstrated positive in semiquantitative adhesion assays than 2 negative strains in semiquantitative adhesion assays. Conclusion The isolations of Staphylococcus epidermidis have the abilities of forming biofilm, and the icaA gene and its normal expression is the important molecular biology foundation of biofilm formation. Other fac-tors maybe involve in the expression of icaA gene in Staphylococcus epidermidis isolates.%目的 检测表皮葡萄球菌临床株生物被膜的形成能力,了解icaA基因及其表达与生物被膜形成的关系.方法 收集205株临床分离表皮葡萄球菌,刚果红平板试验检测其黏附性,半定量黏附试验检测其生物被膜的形成能力,扫描电镜观察生物被膜形态,PCR方法 扩增icaA基因片段,RT-PCR方法 分析icaA基因表达情况.结果 205株表皮葡萄球菌中刚果红平板试验阳性24株,半定量黏附试验阳性22株,28株枪测到icaA基因.半定量黏附试验阳性菌株的icaA基因表达水平呈现高于半定量黏附试验阴性菌株的趋势.结论 表皮葡萄球菌临床株具有一定的形成生物被膜的能力,icaA基因的存在及其正常表达是表皮葡萄球菌形成生物被膜的重要分子生物学基础,icaA基因表达尚有其他因索调控.
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