Mohamed W, Sommer U, Sethi S, Domann E, Thormann U, Schütz I, Lips K S, Chakraborty T, Schnettler R, Alt V
Laboratory of Experimental Trauma Surgery Giessen, Justus-Liebig-University Giessen, D-35394 Giessen,
Eur Cell Mater. 2014 Oct 23;28:258-68. doi: 10.22203/ecm.v028a18.
Staphylococcus aureus is the most clinically relevant pathogen regarding implant-associated bone infection and its capability to invade osteoblasts is well known. The aim of this study was to investigate firstly whether S. aureus is not only able to invade but also to proliferate within osteoblasts, secondly to delineate the mechanism of invasion and thirdly to clarify whether rifampicin or gentamicin can inhibit intracellular proliferation and survival of S. aureus. The SAOS-2 osteoblast-like cell line and human primary osteoblasts were infected with S. aureus EDCC5055 and S. aureus Rosenbach 1884. Both S. aureus strains were able to invade efficiently and to proliferate within human osteoblasts. Immunofluorescence microscopy showed intracellular invasion of S. aureus and transmission electron microscopy images could demonstrate bacterial division as a sign of intracellular proliferation as well as cytosolic bacterial persistence. Cytochalasin D, the major actin depolymerisation agent, was able to significantly reduce S. aureus invasion, suggesting that invasion was enabled by promoting actin rearrangement at the cell surface. 7.5 μg/mL of rifampicin was able to inhibit bacterial survival in SAOS-2 cells with almost complete elimination of bacteria after 4 h. Gentamicin could also kill intracellular S. aureus in a dose-dependent manner, an effect that was significantly lower than that observed using rifampicin. In conclusion, S. aureus is not only able to invade but also to proliferate in osteoblasts. Invasion seems to be associated with actin rearrangement at the cell surface. Rifampicin is effective in intracellular eradication of S. aureus whereas gentamicin only poorly eliminates intracellularly replicating bacteria.
金黄色葡萄球菌是与植入物相关骨感染最具临床相关性的病原体，其侵袭成骨细胞的能力是众所周知的。本研究的目的，一是调查金黄色葡萄球菌是否不仅能够侵袭成骨细胞，还能在其中增殖；二是描述其侵袭机制；三是阐明利福平或庆大霉素是否能抑制金黄色葡萄球菌在细胞内的增殖和存活。用金黄色葡萄球菌EDCC5055和金黄色葡萄球菌Rosenbach 1884感染SAOS-2成骨样细胞系和人原代成骨细胞。两种金黄色葡萄球菌菌株均能有效侵袭并在人成骨细胞内增殖。免疫荧光显微镜检查显示金黄色葡萄球菌的细胞内侵袭，透射电子显微镜图像可证明细菌分裂是细胞内增殖以及胞质细菌持续存在的标志。主要的肌动蛋白解聚剂细胞松弛素D能够显著减少金黄色葡萄球菌的侵袭，这表明侵袭是通过促进细胞表面的肌动蛋白重排实现的。7.5μg/mL的利福平能够抑制SAOS-2细胞中的细菌存活，4小时后细菌几乎完全被清除。庆大霉素也能以剂量依赖的方式杀死细胞内的金黄色葡萄球菌，但其效果明显低于使用利福平观察到的效果。总之，金黄色葡萄球菌不仅能够侵袭成骨细胞，还能在其中增殖。侵袭似乎与细胞表面的肌动蛋白重排有关。利福平在细胞内根除金黄色葡萄球菌方面有效，而庆大霉素在消除细胞内复制的细菌方面效果不佳。
