BACKGROUND The aim of the study was to establish an experimental chronic musculoskeletal infection model in vivo characterized by (a) a small bacterial inoculum, (b) no general or local signs of infection, (c) several parallels (implants) in each animal and finally (d) a model that is technically easy to perform. METHODS Bone xenografts with steel plates were implanted intramuscularly in rats. To the xenografts, different inocula of Staphylococcus aureus and two strains of Staphylococcus epidermidis were added. The animals were observed for different time periods before the removal of the xenografts. The xenografts and steel plates were subjected to quantitative bacterial culture after sonication. Additional steel plates were subjected to scanning electron microscopy (SEM) for visualization of biofilm formation. RESULTS Inoculation of bone grafts with S. aureus did produce a pyogenic infection in all animals. A chronic infection was established in rats where the bone grafts were inoculated with S. epidermidis. A bacterial inoculum of 100 colony-forming units (CFU) of S. epidermidis was adequate as a minimum infective dose. During a period of up until 42 days, the animals infected with S. epidermidis had no general or local signs of infection. According to the results of the quantitative bacterial culture of sonicate fluid and SEM, a biofilm was developed on all implants. CONCLUSION In the present in vivo model, a very small bacterial inoculum succeeded in establishing a chronic musculoskeletal implant infection where a biofilm was formed on the implants. The experimental model is easy to perform and allows several implants in each animal. The model could be useful for the study of biofilm formation in vivo on different implants and different surfaces.

中文翻译：

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建立用于慢性肌肉骨骼植入物感染的体内大鼠模型。

背景技术本研究的目的是建立一种体内实验性慢性肌肉骨骼感染模型，其特征为：（a）小细菌接种物；（b）没有一般或局部感染迹象；（c）每只动物中有几处相似之处（植入物）；最后（d）在技术上易于执行的模型。方法将大鼠钢板异种骨移植肌内。在异种移植物中，加入不同的金黄色葡萄球菌接种物和两种表皮葡萄球菌菌株。在去除异种移植物之前观察动物不同的时间段。超声处理后，异种移植物和钢板进行定量细菌培养。另外的钢板经受扫描电子显微镜（SEM）以观察生物膜形成。结果用金黄色葡萄球菌接种骨移植物确实在所有动物中产生化脓性感染。在大鼠中建立了慢性感染，在其中向表皮葡萄球菌接种了骨移植物。100个表皮葡萄球菌集落形成单位（CFU）的细菌接种物足以作为最小感染剂量。在长达42天的时间内，被表皮葡萄球菌感染的动物没有一般或局部感染迹象。根据超声液和SEM的定量细菌培养结果，在所有植入物上均形成了生物膜。结论在目前的体内模型中，很小的细菌接种物成功地建立了慢性肌肉骨骼植入物感染，在植入物上形成了生物膜。实验模型易于执行，并允许在每只动物中植入多个植入物。