Hepatic survival and population dynamics of extraintestinal pathogenic Escherichia coli

摘要 肠外致病性大肠杆菌（ExPEC）包括一大类大肠杆菌。大肠杆菌分离株， 肠道外疾病，是人类临床菌血症的最常见原因之一。最 进入循环系统的细菌被组织中的巨噬细胞捕获并杀死， 肝脏与相关的大肠杆菌和大肠杆菌限制性致病性E.大肠杆菌，ExPEC分离株具有 在这些肝脏防御中存活更长时间的机制。为了揭示这些机制背后的基因， 我们对从小鼠肝脏中分离的ExPEC进行了基因组规模的转座子插入测序筛选 在用ExPEC转座子插入文库静脉内注射小鼠后，这个屏幕显示了一个核心 肝脏中最佳ExPEC适应性所需的一组基因，其中约90%编码以下组分或调节剂： 手机信封出乎意料的是，分析转座子插入突变体的群体水平分布 揭示了肝脏内细菌的随机子集以克隆方式扩张。总之，这些观察 这两个核心假设将在本提案中探讨：1）ExPEC途径，控制不同的 细胞被膜稳态轴保护细菌对抗肝巨噬细胞以维持细菌存活，并且 2)肝巨噬细胞和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。从拟议的研究中得出的结果， 以病原体和宿主为中心的方法，将提供关于ExPEC如何在体内生存和 从肠外器官中清除最终，这些基本的见解可能有助于发展 加速清除全身性感染的治疗策略。

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.