RmpA, a unique virulence regulator in emerging Klebsiella pneumoniae

描述（由申请人提供）：肠杆菌科包括一系列人类、动物和植物病原体。人类肠道和肠外感染是由密切相关的菌种埃希氏菌、志贺氏菌、沙门氏菌和克雷伯氏菌的特定菌株引起的。尽管研究相对较少，但肺炎克雷伯氏菌仍然是一种臭名昭著的医院病原体，导致抗生素耐药性的广泛传播。最近，K。肺炎克雷伯氏菌已被确定为一种新出现的社区获得性化脓性肝脏感染的原因，称为KLA（K. pneumoniae）。肺炎肝脓肿）。这种感染是由于表达Hmv（高粘膜粘度）表型的特异性克隆，这是由胶囊组成或合成的未知修饰引起的。荚膜是K. Hmv对KLA株的毒力有重要影响。Hmv表型依赖于辅助调节因子RmpA，这是一种独特的蛋白质，可能与全局RcsB反应调节因子形成异二聚体。表征的菌株在移动的遗传元件上含有多个rmpA等位基因。与NIAID的相关性以及该项目的长期目标是识别和理解K的遗传决定因素。pneumoniae的致病性和毒力。本研究的目的是对一株KLA强毒株进行遗传和生化分析。肺炎。研究旨在确定RmpA和相互作用调节因子在控制毒力因子（包括荚膜和Hmv表型）中的功能。研究将与KLA研究的领导者，国立台湾大学医学院的王进镇教授合作。具体目标将应用多种体内和体外方法来检验五种假设：（1a）重复的rmpA等位基因至少部分是冗余的;（1b）RmpA整合到RcsB调控网络中;（2）RmpA调节子包括直接参与荚膜合成和组装的毒力基因以外的毒力基因;（3a）RcsB-RmpA异二聚体控制荚膜生物合成操纵子表达;（3）RmpA调节子包括与RmpA调节子相关的毒力基因。和（3b）RmpA活性受磷酸化调节。拟议研究的影响是：（i）鉴定和分析一种以产生抗生素耐药性而臭名昭著的新兴病原体中的毒力因子;（ii）提高对独特Hmv表型及其由RmpA调节子控制的理解;以及（iii）修改有关全球RcsB调节网络与辅助调节剂相互作用的概念。 公共卫生相关性：肺炎克雷伯氏菌是一种臭名昭著的院内致病菌，最近已成为健康成人化脓性肝脓肿的病因。高粘囊是细胞表面的一层保护层，对这种病理学很重要。这项研究的公共卫生相关性是了解一种独特的调节剂，控制高粘胶囊的形成和组成。

DESCRIPTION (provided by applicant): The family Enterobacteriaceae includes an array of human, animal and plant pathogens. Human intestinal and extraintestinal infections are caused by specific strains of the closely-related species Escherichia, Shigella, Salmonella and Klebsiella. Although relatively little-studied, Klebsiella pneumoniae nevertheless is a notorious nosocomial pathogen responsible for widespread dissemination of antibiotic resistance. Recently, K. pneumoniae has been identified as the cause of an emerging community-acquired pyogenic liver infection termed KLA (K. pneumoniae liver abscess). This infection is due to specific clones expressing the Hmv (hypermucoviscosity) phenotype, which results from unknown modifications of capsule composition or synthesis. Capsule is an essential pathogenicity factor for K. pneumoniae infections, and Hmv is important for virulence of KLA strains. The Hmv phenotype depends on the auxiliary regulator RmpA, a unique protein that likely forms heterodimers with the global RcsB response regulator. Characterized strains contain multiple rmpA alleles on mobile genetic elements. The relevance to NIAID, and the long-term objectives for this project, are to identify and understand genetic determinants for K. pneumoniae pathogenicity and virulence. The goal of this proposal is to initiate genetic and biochemical analysis in a virulent KLA strain of K. pneumoniae. Studies are designed to identify the functions of RmpA and interacting regulators in the control of virulence factors including capsule and the Hmv phenotype. Research will be in collaboration with a leader in the study of KLA, Prof. Jin-Town Wang at the National Taiwan University College of Medicine. Specific aims will apply a variety of in vivo and in vitro approaches to test five hypotheses: (1a) Duplicate rmpA alleles are at least partially redundant; (1b) RmpA is integrated into the RcsB regulatory network; (2) The RmpA regulon includes virulence genes beyond those involved directly in capsule synthesis and assembly; (3a) RcsB-RmpA heterodimers control capsule biosynthetic operon expression; and (3b) RmpA activity is modulated by phosphorylation. Impacts of the proposed research are: (i) identification and analysis of virulence factors in an emerging pathogen notorious for developing antibiotic resistance; (ii) improved understanding of the unique Hmv phenotype and its control by the RmpA regulon; and (iii) modified concepts regarding global RcsB regulatory network interactions with auxiliary regulators. PUBLIC HEALTH RELEVANCE: Klebsiella pneumoniae, a notorious nosocomial pathogen, has emerged recently as the cause of pyogenic liver abscess in otherwise healthy adults. Hypermucoviscous capsule, a protective layer surrounding the cell surface, is important for this pathology. The public health relevance of this research is to understand a unique regulator that controls hypermucoviscous capsule formation and composition.