表皮葡萄球菌纤维蛋白原结合基因（fbe基因）的致病性

Study on the pathogenicity of the gene encoding a fibrinogen-binding protein （fbe gene） from Stuphylococcus epidermidis

目的研究表皮葡萄球菌（表葡菌）纤维蛋白原结合基因（fbe基因）的致病性。方法采用同源基因重组技术构建表葡菌fbe基因缺失突变菌株，得到除fbe基因以外遗传背景相同的fbe基因阳性菌株和阴性菌株。然后建立表葡菌致大鼠导管相关性感染模型，比较fbe基因阳性菌株HB与其fbe基因缺失突变菌株HB—ermB体内致病性的差异，同时采用ELISA测定并比较fbe基因阳性和fbe基因阴性两组表葡菌体外与纤维蛋白原的结合力。结果构建获得表葡菌HB的fbe基因缺失突变菌株HB-ermB，并建立大鼠导管相关性感染模型。fbe基因阳性菌株与纤维蛋白原的体外结合力显著高于fbe基因阴性菌株（P〈0．01）。fbe基因阳性表葡菌HB致大鼠导管相关性感染的发生率为100％（15／15），而fbe基因缺陷株HB-ermB仅导致20％（3／15）的大鼠发生感染，经Fisher精确检验法分析HB组感染率明显高于HB-ermB组，差异有统计学意义（P〈0．01）。HB组导管表面、血液及组织中检测到的细菌数明显高于HB-ermB组，差异有统计学意义（P〈0．01）。结论fbe基因缺陷株致病力较其亲本株明显降低，提示fbe基因为表葡菌的重要致病因子之一。

Objective To study the pathogenicity of fbe gene from Staphylococcus epidermi- dis. Methods Homologous recombination method was used to acquire Staphylococcus epidermidis HB-ermB, a Staphylococcus epidermidis is mutant with fbe deletion, which had the same gene back- ground as fbe-positive strain HB except fbe gene. A rat central venous catheter（CVC） infection mod el was established to compare the in vivo pathogenicity of Staphylococcus epidermidis HB with Staphylococcus epidermidis HB-ermB. Meanwhile, an ELISA method was used to compare the in vitro adhesion to fibrinogen（Fg） between fbe positive and fbe negative strains. Results The fbe deleted mutant. Staphylococcus epidermidis HB-ermB, was constructed. There was significant difference in adhesion to Fg between fbe-positive and fbe-negative strains in vitro （P 〈0. 01）. The infection rate of HB group （ 100 %） was significantly higher than that of HB-ermB group （20 %）. The colony forming units（CFU） recovered from catheters, blood and tissues of HB group were more than those of H B ermB group, and the differences were all significant （P 〈 0.01）. Conclusions Defect of fbe gene could reduce pathogenicity of Staphylococcus epidermidis, implying that fbe gene is an important factor for inducing Staphylococcus epidermidis infection.