Mechanisms of S. aureus transmission and persistence.

描述(申请人提供)：社区相关金黄色葡萄球菌(CA-SA)，例如美国流行的耐甲氧西林菌株USA300，在过去十年中导致皮肤和软组织感染的急剧增加。其中一些感染也是侵袭性的，通常发生在其他健康的人身上。CA-SA似乎具有增强的传播和入侵能力，尽管我们对它们如何在社区中传播和持续存在的了解有限。菌株很可能通过较小的基因修改来适应环境，并变得更适合生态环境。我们通过对从同一家庭纵向收集的密切相关的USA300菌株进行测序，获得了随着时间的推移离散遗传适应原理的证据。与此同时，原来的人畜共患病菌株ST398 MSSA似乎正在曼哈顿北部出现，没有任何动物接触。它现在是我们临床传染性MSSA分离株中最流行的菌株之一，具有在人与人之间传播的非凡能力，并在殖民环境家庭表面显示出更高的存活率。这项研究的总体目标是用流行病学和遗传学相结合的方法，以流行已久的USA300和进化中的人畜共患病菌株ST398为例，确定成功的金黄色葡萄球菌菌株适应其环境生态位时的传播和持续机制。具体地说，这项建议的目的是(1)确定USA300最近的基因变化对金黄色葡萄球菌适应性和环境适应的功能影响，(2)确定ST398在曼哈顿北部的宿主和传播方式，以及(3)确定猪株ST398是如何进化为人类病原体的。我们将首先研究USA300突变的体外适应性、存活率和细胞黏附特性，我们假设这些突变已经改变了这些菌株的适应性和存活率。然后，我们将把我们的研究扩展到新兴的ST398，以确定其在曼哈腾北部传播的基础。基于整群设计，我们将采访和培养ST398阳性患者、他们的接触者和接触者，以确定与ST398感染和传播相关的因素。关键的是，这些研究将为比较测序提供样本，并将允许比较人类定植菌株、传染性菌株以及持久性和非持久性菌株。将在USA300研究中实施的功能分析中研究等基因突变体的序列差异。我们预计，这项工作将有助于确定ST398病毒直接在人与人之间传播的遗传特征，并有助于增强适应性和生态适应能力。这项研究与我成为金黄色葡萄球菌发病机制领域的独立医生兼研究员的目标是直接一致的。 金黄色葡萄球菌等细菌可能会感染社区中其他健康的年轻人。我们对这些细菌是如何传播的以及它们为什么持续存在的了解有限。这项研究将有助于找出其中一些菌株是如何生存的，并使我们能够设计干预措施来限制它们的传播。

DESCRIPTION (provided by applicant): Community-associated Staphylococcus aureus (CA-SA), such as USA300, the epidemic methicillin-resistant strain in the US, have led to a dramatic increase of skin and soft tissues infections over the past decade. Some of these infections are also invasive and often occur in otherwise healthy individuals. CA-SA appear to posses an enhanced capacity for both transmission and invasion, though we have limited understanding of how they spread and persist in the community. It is likely that strains adapt with minor genetic modifications to their environment and become more ecologically "fit". We have obtained proof of principle of discrete genetic adaptations over time by sequencing closely related USA300 strains, longitudinally collected from the same households. Concurrently, it appears that the originally zoonotic strain ST398 MSSA is emerging in the Northern Manhattan, without any animal contact. It is now amongst the most prevalent strains of our clinical infectious MSSA isolates, has a remarkable ability to spread from person-to-person, and shows enhanced survival on colonized environmental household surfaces. The overall goal of this study is to define the mechanisms of transmission and persistence of successful S. aureus strains as they adapt to their environmental niches, taking the examples of the well- established epidemic USA300 and the evolving zoonotic strain ST398, by using a combined epidemiologic and genetic approach. Specifically, the aims of this proposal are to (1) define the functional impact on S. aureus fitness and environmental adaptation of recent genetic changes in USA300, (2) define the reservoirs and modes of transmission of ST398 in Northern Manhattan, and (3) determine how the pig strain ST398 has evolved as a human pathogen. We will first study in vitro fitness, survival and cell adhesion properties of mutations of the sequenced later USA300, that we hypothesized have altered the fitness and survival of these strains. We will then extend our studies to the emerging ST398 to define the basis of its transmission in Northern Manhatten. Based on a cluster-based design we will interview and culture ST398 positive subjects, their contacts and contacts of contacts to determine factors associated with acquisition and spread of ST398. Critically, these studies will provide samples for comparative sequencing and will allow for comparison of human colonizing strains, infectious strains, as well as persisting and non-persisting strains. Sequence differences will be studied on isogenic mutants in functional assays implemented in studies on USA300. We anticipate that this work will lead to the identification of genetic traits accounting for the direct person-to-person transmission of ST398 and that contribute to enhanced fitness and ecological adaptation. This research is in direct line with my goal of becoming an independent Physician-investigator in the field of S. aureus pathogenesis. Bacteria such as Staphylococcus aureus can cause infections in otherwise healthy young people in the community. We have limited understanding of how these bacteria spread and why they persist. This research will help to find out how some of these strains survive and enable us to design interventions to limit their spread.