Polyamines in Staphylococcus aureus Physiology and Pathogenesis

描述（由申请方提供）：由革兰氏阳性菌金黄色葡萄球菌引起的疾病是美国每年发病率和死亡率的重要来源。特别是，最近出现的社区获得性耐甲氧西林S。金黄色葡萄球菌（CA-MRSA）是公共卫生官员非常关注的来源。被称为USA-300的CA-MRSA的独特克隆越来越被认为是最危险的新兴病原体之一，因为它具有超强毒力和在公众中传播的倾向。更好地理解CA-MRSA相对于传统S.因此，金黄色葡萄球菌分离株直接涉及全球公共卫生。 多胺包括腐胺、亚精胺和精胺，据报道由所有形式的生命合成。这些聚阳离子化合物对细胞生理学具有高度的多效作用，它们的合成在哺乳动物中是必不可少的。在活跃生长的组织中观察到多胺产生增加，包括炎症和愈合伤口的部位。多胺还调节细菌生理学的许多方面，并且通常促进细菌生长。然而，13个测序的S.金黄色葡萄球菌基因组编码区分S.金黄色葡萄球菌几乎所有其他生物体。更重要的是，外源精胺和亚精胺对S.金黄色葡萄球菌的浓度不影响其他生物体的生长。唯一值得注意的例外是USA-300，它不受精胺或亚精胺的抑制。USA-300拥有一个独特的遗传岛，称为ACME，在其他S。金黄色葡萄球菌谱系，包括其他CA-MRSA克隆。与WT USA-300固有的多胺抗性相反，？ACME突变体对外源精胺和亚精胺敏感。这个岛含有E的同源物。colispeG编码精胺/亚精胺乙酰转移酶（SSAT），我的实验室已经确定这是ACME相关的多胺抗性所必需和充分的。ACME在USA-300 S高毒力中的作用金黄色葡萄球菌已经建立;但ACME提供CA-MRSA的优势的机理理解还没有发展。我们建议，speG介导的多胺抗性可能提供了一个新的解释ACME赋予美国-300的优势。因此，这一建议将测试我们的中心假设：1）宿主多胺的生产是一种新的先天性免疫效应特异性的S。aureus; 2）S.金黄色葡萄球菌代表了一种高度重要的进化适应，提供了多胺抗性并促成了USA-300流行病的出现。 公共卫生相关性：多胺是由所有生物体产生的化合物。它们具有许多功能，并且在快速生长的细胞中大量产生。有趣的是，人类细菌病原体金黄色葡萄球菌似乎是唯一已知的不能合成多胺的生物体。几个完整的基因组序列可用于这种细菌，但没有一个包含典型的多胺生物合成途径。此外，人体中发现的多胺水平对S具有高度毒性。金黄色。唯一的例外是一个新出现的克隆S。金黄色葡萄球菌，称为USA-300，在没有明显危险因素的患者中引起高度侵袭性疾病。这种耐甲氧西林的S.金黄色葡萄球菌（MRSA）菌株已经成为美国和世界范围内与传染病相关的发病率和死亡率的主要原因。我们已经鉴定了USA-300中赋予对宿主多胺抗性的基因。它在USA- 300分离株中存在的遗传岛上编码，但在大多数其他S.金黄色。本提案的目标是： 1.明确表明S。金黄色葡萄球菌不产生多胺，使其与几乎所有其他形式的生命区别开来。 2.了解多胺如何对S.金黄色。 3.证明宿主多胺的产生限制了S.金葡菌病期间。 4.表明USA-300 MRSA的成功部分源于与该菌株相关的多胺抗性。 有了这些信息，我们就可以开始测试调节宿主多胺的产生是否可以预防由MRSA（一种危险且昂贵的人类病原体）引起的侵袭性疾病。

DESCRIPTION (provided by applicant): Disease caused by the gram-positive bacterium, Staphylococcus aureus, represents a significant source of morbidity and mortality annually in the US. Particularly, the recent emergence of community-acquired methicillin-resistant S. aureus (CA-MRSA) is a source of great concern for public health officials. A distinct clone of CA-MRSA known as USA-300 is increasingly appreciated as one of the most dangerous emerging pathogens due to its hypervirulence and its propensity to spread through the general public. A better understanding of the underlying advantages inherent to CA-MRSA over traditional S. aureus isolates therefore pertains directly to global public health. Polyamines including putrescine, spermidine and spermine are reportedly synthesized by all forms of life. These polycationic compounds exert highly pleitropic effects on cellular physiology and their synthesis is essential in mammals. Increased polyamine production is observed in actively growing tissue including sites of inflammation and healing wounds. Polyamines also modulate numerous aspects of bacterial physiology and generally promote bacterial growth. However, none of the 13 sequenced S. aureus genomes encode canonical polyamine biosynthetic pathways distinguishing S. aureus from nearly all other living organisms. More importantly, exogenous spermine and spermidine exert bactericidal effects on S. aureus at concentrations that do not affect the growth of other organisms. The only notable exception is USA-300, which is not inhibited by spermine or spermidine. USA-300 harbors a unique genetic island known as ACME that is not present in other S. aureus lineages, including other CA-MRSA clones. In contrast to the polyamine resistance inherent to WT USA-300, the ?ACME mutant is susceptible to exogenous spermine and spermidine. This island contains a homologue of E. coli speG encoding a spermine/spermidine acetyl transferase (SSAT), which my laboratory has established is necessary and sufficient for ACME-associated polyamine resistance. A role for ACME in the hypervirulence of USA-300 S. aureus has been established; yet a mechanistic understanding of the advantage afforded CA-MRSA by ACME has not been developed. We propose that speG-mediated polyamine resistance may provide a novel explanation for the advantage conferred to USA-300 by ACME. Thus, this proposal will test our Central Hypotheses: 1) Host polyamine production is a novel innate immune effector specific for S. aureus and 2) The acquisition of ACME by S. aureus represents a highly significant evolutionary adaptation providing polyamine resistance and contributing to the emergence of the USA-300 epidemic. PUBLIC HEALTH RELEVANCE: Polyamines are compounds made by all living organisms. They serve many functions and are highly produced in rapidly growing cells. Interestingly, the human bacterial pathogen Staphylococcus aureus appears to be the only known organism that is incapable of synthesizing polyamines. Several complete genomes sequences are available for this bacterium, yet none contain canonical polyamine biosynthetic pathways. Moreover, polyamines at levels found in the human body are highly toxic to S. aureus. The only exception is a newly emerging clone of S. aureus known as USA-300 that causes highly invasive disease in patients with no obvious risk factors. This methicillin-resistant S. aureus (MRSA) strain has become a leading cause of morbidity and mortality associated with infectious disease in the US and worldwide. We have identified the gene in USA-300 that confers resistance to host polyamines. It is encoded on a genetic island present in USA- 300 isolates, but absent from most other strains of S. aureus. The goal of this proposal is to: 1. Show definitively that S. aureus does not make polyamines distinguishing it from nearly all other forms of life. 2. Understand how polyamines exert toxicity towards S. aureus. 3. Demonstrate that host polyamine production limits the proliferation of S. aureus during disease. 4. Show that the success of USA-300 MRSA stems, in part, from the polyamine-resistance associated with this strain. With this information, we can begin to test whether modulating host polyamine production prevents invasive disease caused by MRSA, a dangerous and costly human pathogen.