Periprosthetic joint infection (PJI) occurring after artificial joint replacement is a major clinical issue requiring multiple surgeries and antibiotic interventions. Staphylococcus aureus is the bacterium most commonly responsible for PJI. Recent in vitro research has shown that staphylococcal strains rapidly form aggregates in the presence of synovial fluid (SF). We hypothesize that these aggregates provide early protection to bacteria entering the wound site, allowing them time to attach to the implant surface, leading to biofilm formation. Thus, understanding the attachment kinetics of these aggregates is critical in understanding their adhesion to various biomaterial surfaces. In this study, the number, size, and surface area coverage of aggregates as well as of single cells of S. aureus were quantified under various conditions on different orthopedic materials relevant to orthopedic surgery: stainless steel (316L), titanium (Ti), hydroxyapatite (HA), and polyethylene (PE). It was observed that, regardless of the material type, SF-induced aggregation resulted in reduced aggregate surface attachment and greater aggregate size than the single-cell populations under various shear stresses. Additionally, the surface area coverage of bacterial aggregates on PE was relatively high compared to that on other materials, which could potentially be due to the rougher surface of PE. Furthermore, increasing shear stress to 78 mPa decreased aggregate attachment to Ti and HA while increasing the aggregates’ average size. Therefore, this study demonstrates that SF induced inhibition of aggregate attachment to all materials, suggesting that biofilm formation is initiated by lodging of aggregates on the surface features of implants and host tissues.

中文翻译：

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在不同水平的剪应力作用下，金黄色葡萄球菌聚集在整形外科材料上。

人工关节置换后发生的假肢周围感染（PJI）是一个主要的临床问题，需要多次手术和抗生素干预。金黄色葡萄球菌是引起PJI的最常见细菌。最近的体外研究表明，葡萄球菌菌株在滑液（SF）存在下迅速形成聚集体。我们假设这些聚集体可为进入伤口部位的细菌提供早期保护，使它们有时间附着在植入物表面，从而导致生物膜形成。因此，了解这些聚集体的附着动力学对于了解它们对各种生物材料表面的粘附性至关重要。在这项研究中，聚集体以及单个细胞的数量，大小和表面积覆盖率金黄色葡萄球菌在与骨科手术相关的不同骨科材料上，在各种条件下进行定量：不锈钢（316L），钛（Ti），羟基磷灰石（HA）和聚乙烯（PE）。观察到，无论材料类型如何，在各种剪切应力下，SF诱导的聚集都导致聚集的表面附着减少，聚集尺寸大于单细胞群体。此外，与其他材料相比，PE上细菌聚集体的表面积覆盖率相对较高，这可能是由于PE的表面较粗糙。此外，将剪切应力增加至78 mPa会减少聚集体与Ti和HA的附着，同时增加聚集体的平均尺寸。因此，这项研究表明SF诱导了骨料对所有材料的附着抑制，