Introduction. Biofilm formation is a major virulence factor associated with Staphylococcus aureus infections. However, the influence of plasma proteins on biofilm formation of clinical isolates in vitro remains unclear. Hypotheses. We hypothesized that coating surfaces with plasma proteins might induce biofilm formation by S. aureus of different clonal lineages. Aim. To evaluate biofilm production by clinical S. aureus isolates of different clonal lineages isolated in Rio de Janeiro hospitals and investigated the presence of biofilm-associated genes. Methodology. This study assessed biofilm production of 60 S. aureus isolates in polystyrene microtitre plates with and without fibrinogen or fibronectin. The biochemical composition of the biofilm matrices was determined and the biofilm formation on fibrinogen-coated surfaces was also evaluated by confocal laser scanning microscopy. The presence of biofilm-related genes was detected by PCR, and the typing and functionality of agr operon was also evaluated. Results. Most of the isolates (45 %) were weak biofilm producers or non-producers. However, most of them presented a significant increase in biofilm production on plates covered with plasma proteins. There was no significant difference in biofilm formation between methicillin-resistant and -susceptible S. aureus isolates, or between different clonal lineages, except for ST30-IV (weak producers) and ST239-III (strong producers). The fnbB gene was associated with higher biofilm production. Conclusion. An increase in biofilm production in the presence of plasma proteins highlights the importance of investigating biofilm formation by S. aureus clinical isolates under different conditions since this virulence factor contributes to persistent infections and increased resistance to antimicrobials.

中文翻译：

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金黄色葡萄球菌临床分离物在被血浆蛋白覆盖的表面上形成的生物膜增加

介绍。生物膜形成是与金黄色葡萄球菌感染相关的主要毒力因子。然而，血浆蛋白对体外临床分离物生物膜形成的影响仍不清楚。假设。我们假设用血浆蛋白涂覆表面可能会诱导不同克隆谱系的金黄色葡萄球菌形成生物膜。瞄准。评估在里约热内卢医院分离的不同克隆谱系的临床金黄色葡萄球菌分离物的生物膜产生，并研究生物膜相关基因的存在。方法。本研究评估了 60金黄色葡萄球菌的生物膜产生 在含或不含纤维蛋白原或纤连蛋白的聚苯乙烯微量滴定板上分离。测定了生物膜基质的生化成分，并通过共聚焦激光扫描显微镜评估了纤维蛋白原涂层表面上的生物膜形成。通过 PCR 检测生物膜相关基因的存在，并评估agr 操纵子的分型和功能。结果。大多数分离株 (45%) 是弱生物膜生产者或非生产者。然而，它们中的大多数在覆盖有血浆蛋白的平板上表现出生物膜产生的显着增加。耐甲氧西林和易感的金黄色葡萄球菌在生物膜形成方面没有显着差异 除 ST30-IV（弱生产者）和 ST239-III（强生产者）外，分离株或不同克隆谱系之间存在差异。该fnbB基因具有较高的生物膜的生产相关。结论。在血浆蛋白存在的情况下生物膜产生的增加突出了研究金黄色葡萄球菌临床分离株在不同条件下生物膜形成的重要性，因为这种毒力因子有助于持续感染和增加对抗菌剂的耐药性。