Hepatic survival and population dynamics of extraintestinal pathogenic Escherichia coli

摘要 肠外致病性大肠埃希氏菌(ExPEC)包括一大群引起 肠道以外的疾病，是人类临床菌血症最常见的原因之一。多数 进入循环系统的细菌被驻留在组织中的巨噬细胞捕获并杀死 肝脏。与相关的共生性和肠限制性致病菌相比，ExPEC分离株具有 在这些肝脏防御系统中存活更长时间的机制。为了发现这些机制背后的基因， 我们在从小鼠肝脏分离的ExPEC上进行了基因组规模的转座子插入测序筛选 在小鼠静脉注射ExPEC转座子插入文库后。这张屏幕揭开了一个核心 肝脏最佳ExPEC适合性所需的一组基因，其中约90%编码 手机信封。出乎意料的是，转座子插入突变体的种群水平分布分析 揭示了肝脏内细菌的一个随机子集克隆地扩展。总而言之，这些观察结果 这项提案将探讨的两个中心假设是：1)控制不同 细胞膜动态轴保护细菌免受肝巨噬细胞的攻击，以维持细菌的生存，以及 2)肝巨噬细胞与支持肝内存活的特定细菌基因之间的相互作用 清除过程中病原体在宿主体内的分布情况。拟议研究的结果，这些研究依赖于 以病原体和宿主为中心的方法，将提供ExPEC如何在 清除了肠外器官。归根结底，这些基本见解可能有助于 加速清除全身感染的治疗策略。

ABSTRACT Extraintestinal Pathogenic Escherichia coli (ExPEC) comprise a broad group of E. coli isolates that cause disease outside of the intestine and are among the most common causes of clinical bacteremia in humans. Most bacteria that gain access to the circulatory system are captured and killed by tissue-resident macrophages in the liver. In contrast to related commensal and intestine-restricted pathogenic E. coli, ExPEC isolates possess mechanisms to survive longer within these hepatic defenses. To uncover genes underlying such mechanisms, we performed a genome-scale transposon insertion sequencing screen on ExPEC isolated from murine livers following intravenous injection of mice with an ExPEC transposon insertion library. This screen uncovered a core set of genes required for optimal ExPEC fitness in the liver, ~90% of which encode components or regulators of the cell envelope. Unexpectedly, analysis of the population-level distribution of transposon-insertion mutants revealed that a random subset of the bacteria within the liver expands clonally. Together, these observations underlie the two central hypotheses that will be explored in this proposal: 1) ExPEC pathways that control distinct cell envelope homeostasis axes protect bacteria against liver macrophages to maintain bacterial survival, and 2) interactions between liver macrophages and specific bacterial genes that support intra-hepatic survival govern how the pathogen is distributed within the host during clearance. Findings from the proposed studies, which rely on both pathogen- and host-centric approaches, will provide knowledge of how ExPEC survive within and are cleared from extraintestinal organs. Ultimately, these fundamental insights may assist in the development of therapeutic strategies to accelerate clearance of systemic infections.