Staphylococcus aureus (S. aureus) infections are notoriously complicated by the ability of the organism to grow in biofilms and are difficult to eradicate with antimicrobial therapy. The purpose of the current study was to clarify the influence of sub-inhibitory concentrations (sub-MICs) of daptomycin and tigecycline antibiotics on biofilm adhesion factors and exoproteins expressions by S. aureus clinical isolates. Six clinical isolates representing positive biofilm S. aureus clones (3 methicillin-sensitive S. aureus (MSSA) and 3 methicillin-resistant S. aureus (MRSA)) were grown with sub-MICs (0.5 MIC) of two antibiotics (daptomycin and tigecycline) for 12 h of incubation. RNA extracted from culture pellets was used via relative quantitative real-time-PCR (qRT-PCR) to determine expression of specific adhesion (fnbA, fnbB, clfA, clfB, fib, ebps, cna, eno) and biofilm (icaADBC) genes. To examine the effect of sub-MIC of these antibiotics on the expression of extracellular proteins, samples from the culture supernatants of six isolates were collected after 12 h of treatment with or without tigecycline in order to profile protein production via 2D gel sodium dodecyl sulfate-polyacrylamide gel electrophoresis (2D gel-SDS-PAGE). Sub-MIC treatment of all clinical MRSA and MSSA strains with daptomycin or tigecycline dramatically induced or suppressed fnbA, fnbB, clfA, clfB, fib, ebps, cna, eno, and icaADBC gene expression. Furthermore, sub-MIC use of tigecycline significantly reduced the total number of separated protein spots across all the isolates, as well as decreasing production of certain individual proteins. Collectively, this study showed very different responses in terms of both gene expression and protein secretion across the various isolates. In addition, our results suggest that sub-MIC usage of daptomycin and tigecycline could signal virulence induction by S. aureus via the regulation of biofilm adhesion factor genes and exoproteins. If translating findings to the clinical treatment of S. aureus, the therapeutic regimen should be adapted depending on antibiotic, the virulence factor and strain type.

中文翻译：

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达托霉素和替加环素亚抑制浓度在调节金黄色葡萄球菌毒力中的作用

众所周知，金黄色葡萄球菌（S. aureus）感染会因生物体在生物膜中生长的能力而变得复杂，并且很难用抗微生物疗法根除。本研究的目的是阐明达托霉素和替加环素抗生素的亚抑制浓度（sub-MICs）对金黄色葡萄球菌临床分离株生物膜粘附因子和外蛋白表达的影响。六个代表生物膜金黄色葡萄球菌阳性克隆的临床分离株（3个对甲氧西林敏感的金黄色葡萄球菌（MSSA）和3个对耐甲氧西林的金黄色葡萄球菌（MRSA））与两种抗生素（达托霉素和替加环素）的亚MIC（0.5 MIC）一起培养12小时。通过相对定量实时PCR（qRT-PCR）使用从培养沉淀中提取的RNA来确定特异性粘附（fnbA，fnbB，clfA，clfB，fib，ebps，cna，eno）和生物膜（icaADBC）的表达）基因。为了检查这些抗生素的亚MIC对细胞外蛋白表达的影响，在使用或未使用替加环素处理12小时后，从六个分离株的培养上清液中收集样品，以便通过2D凝胶十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（2D gel-SDS-PAGE）。用达托霉素或替加环素对所有临床MRSA和MSSA菌株进行亚MIC治疗可显着诱导或抑制fnbA，fnbB，clfA，clfB，fib，ebps，cna，eno和icaADBC基因表达。此外，亚MIC的替加环素的使用显着减少了所有分离物中分离出的蛋白质斑点的总数，并降低了某些单个蛋白质的产量。总体而言，这项研究表明在各种分离物中，在基因表达和蛋白质分泌方面都存在非常不同的反应。此外，我们的研究结果表明达托霉素和替加环素的亚MIC使用可能通过调节生物膜粘附因子基因和外蛋白来指示金黄色葡萄球菌的致病性。如果将发现转化为金黄色葡萄球菌的临床治疗，则应根据抗生素，毒力因子和菌株类型来调整治疗方案。