Institut für Medizinische Mikrobiologie, Virologie und Hygiene, Zentrum für Diagnostik, Universitätsklinikum Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany.
Infect Immun. 2011 Jun;79(6):2267-76. doi: 10.1128/IAI.01142-10. Epub 2011 Mar 14.
Assembly of adherent biofilms is the key mechanism involved in Staphylococcus epidermidis virulence during device-associated infections. Aside from polysaccharide intercellular adhesin (PIA), the accumulation-associated protein Aap and the extracellular matrix binding protein Embp act as intercellular adhesins, mediating S. epidermidis cell aggregation and biofilm accumulation. The aim of this study was to investigate structural features of PIA-, Aap-, and Embp-mediated S. epidermidis biofilms in more detail and to evaluate their specific contributions to biofilm-related S. epidermidis immune escape. PIA-, Embp-, and Aap-mediated biofilms exhibited substantial morphological differences. Basically, PIA synthesis induced formation of macroscopically visible, rough cell clusters, whereas Aap- and Embp-dependent biofilms preferentially displayed a smooth layer of aggregated bacteria. On the microscopic level, PIA was found to form a string-like organized extracellular matrix connecting the bacteria, while Embp produced small deposits of intercellular matrix and Aap was strictly localized to the bacterial surface. Despite marked differences, S. epidermidis strains using PIA, Aap, or Embp for biofilm formation were protected from uptake by J774A.1 macrophages, with similarly efficiencies. In addition, compared to biofilm-negative S. epidermidis strains, isogenic biofilm-forming S. epidermidis induced only a diminished inflammatory J774A.1 macrophage response, leading to significantly (88.2 to 88.7%) reduced NF-κB activation and 68.8 to 83% reduced interleukin-1β (IL-1β) production. Mechanical biofilm dispersal partially restored induction of NF-κB activation, although bacterial cell surfaces remained decorated with the respective intercellular adhesins. Our results demonstrate that distinct S. epidermidis biofilm morphotypes are similarly effective at protecting S. epidermidis from phagocytic uptake and at counteracting macrophage activation, providing novel insights into mechanisms that could contribute to the chronic and persistent course of biofilm-related S. epidermidis foreign material infections.
表皮葡萄球菌生物膜的形成是与器械相关感染有关的表皮葡萄球菌毒力的关键机制。除了多糖细胞间黏附素（PIA）外，积累相关蛋白 Aap 和细胞外基质结合蛋白 Embp 也作为细胞间黏附素，介导表皮葡萄球菌细胞聚集和生物膜积累。本研究旨在更详细地研究 PIA、Aap 和 Embp 介导的表皮葡萄球菌生物膜的结构特征，并评估它们对生物膜相关表皮葡萄球菌免疫逃避的特定贡献。PIA、Embp 和 Aap 介导的生物膜表现出显著的形态差异。基本上，PIA 的合成诱导了宏观可见的粗糙细胞簇的形成，而 Aap 和 Embp 依赖的生物膜则优先显示出聚集细菌的光滑层。在微观水平上，发现 PIA 形成了一种串状的细胞外基质，将细菌连接起来，而 Embp 产生了小的细胞间基质沉积物，Aap 则严格定位于细菌表面。尽管存在明显差异，但使用 PIA、Aap 或 Embp 形成生物膜的表皮葡萄球菌菌株都能免受 J774A.1 巨噬细胞的摄取，效率相似。此外，与生物膜阴性的表皮葡萄球菌菌株相比，同源生物膜形成的表皮葡萄球菌仅诱导 J774A.1 巨噬细胞的炎症反应减弱，导致 NF-κB 激活显著降低（88.2%至 88.7%），白细胞介素-1β（IL-1β）产生降低 68.8%至 83%。机械性生物膜分散部分恢复了 NF-κB 激活的诱导，尽管细菌细胞表面仍被相应的细胞间黏附素所装饰。我们的结果表明，不同的表皮葡萄球菌生物膜形态同样有效地保护表皮葡萄球菌免受吞噬作用，并抵抗巨噬细胞激活，为可能导致生物膜相关表皮葡萄球菌异物感染慢性和持续性的机制提供了新的见解。
