Department of Urology, First Affiliated Hospital of People's Liberation Army General Hospital, Beijing, China.
Chin Med J (Engl). 2013 Jul;126(14):2647-51.
The catheter related infection caused by Staphylococcus epidermidis biofilm is increasing and difficult to treat by antimicrobial chemotherapy. The properties of biofilms that give rise to antibiotic resistance are only partially understood. This study aimed to elucidate the penetration of erythromycin through Staphylococcus epidermidis biofilm.
The penetration ratio of erythromycin through Staphylococcus epidermidis biofilms of 1457, 1457-msrA, and wild isolate S68 was detected by biofilm penetration model at different time points according to the standard regression curve. 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 cultivation for 36 hours were 0.93, 0.55 and 0.4, respectively. The erythromycin penetration ratio through 1457 biofilm (0.58 after 8 hours) was higher than that through the other two (0.499 and 0.31 after 24 hours). Lower 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 to the Staphylococcus epidermidis biofilm, but could not kill the cells thoroughly. The lower growth rate of the cells within biofilm could help decreasing the erythromycin susceptibility.
表皮葡萄球菌生物膜引起的导管相关感染正在增加，并且难以通过抗菌化疗治疗。生物膜导致抗生素耐药性的特性仅部分被理解。本研究旨在阐明红霉素穿透表皮葡萄球菌生物膜的能力。
根据标准回归曲线，通过生物膜渗透模型检测 1457、1457-msrA 和野生分离株 S68 的表皮葡萄球菌生物膜在不同时间点的红霉素穿透率。通过共聚焦激光显微镜和透射电镜观察生物膜内的 RNA/DNA 比值和细胞密度。
培养 36 小时后，红霉素通过 1457、1457-msrA 和 S68 生物膜的穿透率分别为 0.93、0.55 和 0.4。红霉素通过 1457 生物膜的穿透率（培养 8 小时后为 0.58）高于其他两种生物膜（培养 24 小时后为 0.499 和 0.31）。通过吖啶橙染色的共聚焦激光显微镜观察到生物膜内细胞生长速度较慢，RNA/DNA 比例降低。与透射电镜观察的对照组相比，生物膜气面的细胞密度低于琼脂面，细胞碎片较多。
红霉素可以穿透表皮葡萄球菌生物膜，但不能彻底杀死细胞。生物膜内细胞生长速度较慢有助于降低红霉素的敏感性。
