Mechanisms of S. aureus transmission and persistence.

描述（由申请人提供）：社区相关性金黄色葡萄球菌（CA-SA），如USA300，是美国流行的耐甲氧西林菌株，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入性的，通常发生在健康的个体身上。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。菌株很可能通过轻微的基因修改来适应它们的环境，从而在生态上变得更加“适合”。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，我们已经获得了离散遗传适应原理的证据。同时，似乎最初的人畜共患病ST398 MSSA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分离株中最普遍的菌株之一，具有显著的人际传播能力，并且在定植的环境家庭表面上显示出更高的存活率。本研究的总体目标是通过使用流行病学和遗传学相结合的方法，以已确定的流行病USA300和正在进化的人畜共患菌株ST398为例，确定成功的金黄色葡萄球菌菌株在适应其环境利基时的传播和持久性机制。具体来说，本提案的目的是：(1)确定USA300最近的遗传变化对金黄色葡萄球菌适应性和环境适应性的功能影响，(2)确定ST398在曼哈顿北部的储存库和传播模式，以及(3)确定猪株ST398如何进化为人类病原体。我们将首先研究测序后的USA300突变的体外适应性、存活和细胞粘附特性，我们假设这些突变改变了这些菌株的适应性和存活。然后，我们将研究扩展到新兴的ST398，以确定其在曼哈顿北部传播的基础。基于集群设计，我们将采访和培养ST398阳性受试者，他们的联系人和联系人的联系人，以确定与ST398获取和传播相关的因素。至关重要的是，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，感染菌株以及持续和非持续菌株。序列差异将在USA300研究中实施的功能分析中研究等基因突变体。我们预计这项工作将导致确定ST398直接人际传播的遗传性状，并有助于增强适应性和生态适应性。这项研究直接符合我成为金黄色葡萄球菌发病机制领域独立医师调查员的目标。

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.