Mechanisms underlying the pathogenic potential of cardioinvasive L. monocytogenes

描述(由申请人提供)：侵袭性心脏感染是单核细胞增多性李斯特菌发病机制中一个公认但知之甚少的方面。对选定的单核细胞增多性李斯特菌分离株的初步检查表明，亚群的菌株表现出更强的侵袭和感染心脏组织的能力。据推测，这些心脏侵袭性菌株已经开发出新的机制和/或表达新的或改变的因子，使它们能够在心脏组织内复制。本项目的目标将是阐明心脏侵袭性单核细胞增多性李斯特菌分离株以心脏为目标进行细菌复制的机制(S)。该项目的目的是阐明单核细胞增多性李氏杆菌心脏感染的过程和病理，以及确定导致向心性增加的细菌因素。小鼠感染模型将被用来确定心脏侵袭性单核细胞增多性李斯特菌菌株的时间进程和组织分布。将使用含有Lux报告融合的单核细胞增多性李氏杆菌菌株的生物发光成像来监测小鼠体内的感染情况，随后将使用靶组织的组织学检查来进一步阐明发病机制和宿主炎症反应。对心脏侵袭性和非心脏侵袭性菌株的比较基因组分析将与遗传方法结合使用，以确定导致细菌入侵和在心肌细胞内复制的细菌因素。将在一种高心脏侵袭性菌株中使用转座子插入突变和细菌插入文库的生成，以使能够识别有助于在心肌细胞内入侵和复制的细菌因子。这些文库将被筛选出缺乏在心脏细胞系内入侵和复制能力的突变体。对这些突变体的遗传分析将被用来阐明导致心脏侵袭性菌株嗜心性的毒力机制。从这些研究中获得的信息可能最终能够在患者感染早期以及在食源性暴发中识别出嗜心性菌株，从而增加对高危个人成功诊断和治疗的可能性。 公共卫生相关性：心脏感染是单核细胞增多性李斯特氏菌致病机制中一个重要但特征不佳的方面。单核细胞增多性李斯特氏菌临床分离株的亚群表现出更强的定植受感染动物心脏的能力，我们的目标是阐明这种感染模式的机制。该项目的成果可能导致在感染或暴发过程早期快速识别此类菌株的方法，有可能导致更好的治疗方法和结果。

DESCRIPTION (provided by applicant): Invasive cardiac infections are a recognized yet poorly understood facet of Listeria monocytogenes pathogenesis. Preliminary examinations of selected L. monocytogenes isolates indicates that a sub-population of strains exhibit an enhanced ability to invade and infect cardiac tissue. It is hypothesized that these cardioinvasive strains have developed novel mechanisms and/or express novel or altered factors that enable them to replicate within cardiac tissue. The goal of this project will be to elucidate the mechanism(s) by which cardioinvasive isolates of L. monocytogenes target the heart for bacterial replication. The aims of this project are designed to elucidate the course and pathology of cardiac infection by L. monocytogenes as well as to identify bacterial factors responsible for increased cardio-tropism. Mouse models of infection will be used to define the time course and tissue distribution of cardioinvasive strains of L. monocytogenes. In vivo infections in mice will be monitored using bioluminescence imaging of L. monocytogenes strains containing lux reporter fusions, and subsequent histological examination of target tissues will be used to further elucidate pathogenesis and host inflammatory response. Comparative genomic analysis of cardioinvasive and noncardioinvasive strains will be used in combination with genetic approaches to identify bacterial factors that contribute to bacterial invasion and replication within cardiac cells. The use of transposon insertion mutagenesis in a highly cardioinvasive strain and the generation of bacterial insertion libraries will be done to enable the identification of bacterial factors that contribute to invasion and replication within cardiac cells. The libraries will be screened for mutants that lack the ability to invade and replicate within cardiac cell lines. Genetic analyses of these mutants will be used to elucidate virulence mechanisms responsible for the cardiotropism of cardioinvasive strains. The information gained from these studies may ultimately enable the identification of cardiotropic strains early in the patient infection as well as in food-borne outbreaks, so as to increase the likelihood of successful diagnosis and treatment of at-risk individuals. PUBLIC HEALTH RELEVANCE: Cardiac infections represent a significant but poorly characterized facet of Listeria monocytogenes pathogenesis. Sub-populations of clinical isolates of L. monocytogenes exhibit an enhanced ability to colonize the hearts of infected animals, and our goal is to elucidate the mechanisms responsible for this mode of infection. The outcomes of this project may lead to methods of rapidly identifying such strains early in the course of an infection or outbreak, potentially leading to better treatment methods and outcomes.