表皮葡萄球菌生物被膜对红霉素渗透性的研究

The Erythromycin Penetration Through Staphylococcus epidermidis Biofilm

为探讨表皮葡萄球菌生物被膜对红霉素的渗透性,我们采用生物被膜抗生素渗透模型检测Staphylcoccus epidermidis1457、1457-msrA和临床分离株S68生物被膜不同时间点红霉素的渗透率,并用吖啶橙染色激光共聚焦显微镜观察生物被膜内细菌RNA/DNA的相对含量;扫描电子显微镜观察膜内细菌的密度。红霉素作用36h后,1457、1457-msrA、S68的渗透率分别为0.93,0.55和0.4;1457渗透地较快,8h后渗透率即达到0.58,而1457msrA和S68相对较为缓慢,24h后分别为0.499和0.31;吖啶橙染色可见红霉素作用下膜内菌RNA和DNA的相对比例减小,生长速率下降;扫描电子显微镜观察可见生物被膜红霉素作用后空气面的细菌数与琼脂面相比均较少,细胞碎片相对较多,而对照组(无抗生素作用)琼脂面和空气面的细菌密度和分布较均匀。可见红霉素可渗透入表葡菌生物被膜,但不能完全杀死膜内细菌;膜内细菌在生物被膜环境中生长速率下降,有助于降低细菌对红霉素的敏感性。

To explore the erythromycin penetration through Staphylococcus epiderrnidis biofilm. The penetration ratio of erythromycin through Staphylococcus epidermidis biofilm of 1457, 1457-msrA and S68 isolates were detected by biofilm penetration model at different time points. The RNA/DNA ratio and the cell density within the biofilms were observed by confocal laser microscope and transmission electromicroscope, respectively. The penetration ratios of erythromycin through the biofilms of 1457, 1457-msrA and S68 after 36 h were 0.93, 0.55 and 0.4, respectively. The erythromycin penetration ratio through 1457 biofilm （with 0.58 after 8 h） was faster than two others （with 0.499 and 0.31 after 24 h）. The slower growth rate of the cells in biofilm was shown, with reduction of RNA/DNA proportion observed by confocal laser microscope through acridine orange stain. Compared with the control group observed by transmission electrmicroscope, the cell density of biofilm air face was lower than that of agar face, with more cell debris. Erythromycin could penetrate into the Staphylococcus epidermidis biofilm, but couldn＇t kill the cells thoroughly. The lower growth rate of the cells within biofilm could help to decrease the erythromycin susceptibility.