Regulation of biofilm formation in Staphylococcus aureus

葡萄球菌是植入性医疗器械相关感染的主要原因。生物膜的产生是这类感染发病机制的一个重要方面。多糖β-1，6-连接的N-乙酰葡糖胺（PNAG）对金黄色葡萄球菌和共凝集酶阴性葡萄球菌（ConNS）中的生物膜形成至关重要，并且由细胞间粘附（伊卡）基因座编码的蛋白质合成。 本研究的目的是描述伊卡位点在S.金黄色。而S. epidermidis组成性地形成生物膜，S.金黄色葡萄球菌在典型的体外条件下不产生PNAG，但需要刺激，如缺铁或>0.5%葡萄糖。临床分离的S.金黄色葡萄球菌MN 8发生自发突变，导致PNAG的组成性过量产生。在本研究的第一部分中，将来自PNAG组成型菌株（MN 8 m）的伊卡位点的DNA序列与来自PNAG诱导型菌株的ica位点的DNA序列进行比较。将通过北方分析和伊卡启动子结合蛋白的DNA亲和力来评估MN 8 m伊卡的能力。最后，将MN 8 m的毒力与PNAG诱导的S.金黄色葡萄球菌在肾脏感染的小鼠模型中。

The staphylococci are the leading cause of infections related to implantable medical devices. Biofilm production is an important aspect of the pathogenesis of such infections. The polysaccharide beta-1,6- linked N-acetylglucosamine (PNAG) is critical to biofilm elaboration in both Staphylococcus aureus and co-agulase-negative staphylococci (ConNS) and is synthesized from proteins encoded in the intercellular adhesion (ica) locus. The goal of this study is to characterize the mechanism through which the ica locus is regulated in S. aureus. Whereas S. epidermidis elaborates biofilm constitutively, S. aureus does not produce PNAG under typical in vitro conditions but requires a stimulus, such as iron deprivation or >0.5% glucose. A clinical isolate of S. aureus, MN8, underwent a spontaneous mutation resulting in constitutive over-production of PNAG. In the first part of this study, the DNA sequence of the ica locus from the PNAG-constitutive strain (MN8m) will be compared with that of PNAG-inducible strains of S. aureus and the ability of MN8m ica will e assessed by Northern analysis and via DNA affinity of ica promoter-binding proteins. Finally, virulence of MN8m will be compared with that of PNAG-inducible strains of S. aureus in the mouse model of renal infection.