Regulation of biofilm formation in Staphylococcus aureus

葡萄球菌是与植入式医疗设备相关的感染的主要原因。生物被膜的产生是这类感染发病机制的一个重要方面。β-1，6-连接N-乙酰氨基葡萄糖(PNAG)是金黄色葡萄球菌和共凝胶酶阴性葡萄球菌(Conns)生物膜形成的关键分子，由细胞间黏附(ICA)基因编码的蛋白质合成。本研究的目的是研究金黄色葡萄球菌ICA基因座的调控机制。尽管表皮葡萄球菌从组成上阐述了生物被膜，但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。金黄色葡萄球菌临床分离株MN8发生自发突变，导致PNAG结构性过量产生。在本研究的第一部分，将PNAG构成株(MN8m)的ICA基因座的DNA序列与PNAG诱导的金黄色葡萄球菌进行比较，并通过Northern分析和ICA启动子结合蛋白的DNA亲和力来评估MN8m ICA的能力。最后，在小鼠肾脏感染模型中，将MN8M的毒力与PNAG诱导的金黄色葡萄球菌的毒力进行比较。

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.