Ecological population structure and emergence of virulent Vibrio parahaemolyticus

副溶血弧菌的生态种群结构和强毒力的出现

• 批准号: 7573549
• 负责人: Vaughn Cooper
• 金额: $ 7万
• 依托单位: UNIVERSITY OF NEW HAMPSHIRE
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-05-22 至 2011-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7573549
• 关键词: Acute; Address; Area; Bacteria; Biological Assay; Biology; Carbon; Chlorophyll; Chromosome Mapping; Chromosomes; Climate; Communicable Diseases; Communities; Country; Data; Detection; Disease; Disease Outbreaks; Ecology; Elements; Environment; Environmental Risk Factor; Epidemic; Evolution; Food Supply; Frequencies; Gastroenteritis; Gene Transfer; Genes; Genetic; Genetic Recombination; Genetic Structures; Genetic Variation; Genotype; Health; Hospitalization; Human; Incidence; Individual; Infection; Inflammatory; Investigation; Investments; Knowledge; Lead; Learning; Left; Light; Link; Location; Minority; Modeling; Molecular; Molecular Genetics; Monitor; New Hampshire; Nitrogen; Organism; Oxygen; Oysters; Pan Genus; Pathogenicity; Phenotype; Phosphorus; Population; Population Dynamics; Population Genetics; Prevalence; Protocols documentation; Publishing; Recording of previous events; Relative (related person); Research; Research Personnel; Risk; Scheme; Seasons; Shellfish; Site; Solid; Source; Structure; Study models; Temperature; Testing; Time; Vibrio; Vibrio parahaemolyticus; Virulence; Virulent; Water; Wound Infection; base; climate change; coastal water; cytotoxic; cytotoxicity; environmental change; experience; foodborne illness; insight; land use; pandemic disease; pathogen; predictive modeling; prevent; programs; public health relevance; stem; trait; warm temperature

DESCRIPTION (provided by applicant): Numerous infectious diseases are caused by minority strains within otherwise nonpathogenic species, but the ecological and population genetic mechanisms that drive their emergence remains unclear. Understanding these dynamics is especially important in light of the increasing frequency of many epidemics tied to changes in climate and land use. For example, illness caused by contaminated shellfish is relatively infrequent in most of the U.S. but incidence is on the rise and beginning to parallel that of warmer countries. The abundance of the major causative bacterium Vibrio parahaemolyticus (Vp) is positively correlated with warmer waters with moderate salinity. Yet these ecological variables do not sufficiently predict Vp epidemics in part because the relative abundance of potentially pathogenic Vp is far less predictable. This project seeks to identify and quantify the ecological factors that influence the relative prevalence of virulent Vp in oysters. Our model study area, the Great Bay estuary of New Hampshire, is ideal because of the wide range of environmental conditions that occur over relatively small spatial scales, and because its warmer waters promote species typically associated with warmer climates. Vp are known to reside in this estuary along with other pathogenic Vibrios and there have been several acute Vp infections from the estuary suggesting that minority pathogenic strains are resident in the community. Our focal question is: how do environmental factors drive the population dynamics of Vp? We hypothesize that Vp strains that vary in virulence traits are associated with certain environmental variables, such that fluctuations in climate will specifically influence the relative abundance of virulent Vp. We base this hypothesis on our preliminary data that shows a significant correlation between the prevalence of highly cytotoxic strains and increased temperature. Using multi-locus sequence typing analysis (MLST), we will examine the population structure and extent of recombination between estuary isolates. Our preliminary genetic typing thus far suggests that there is significant genetic exchange within the community that has three distinct Vp populations. The proposed study is unique from those published, specifically by 1) the inclusion of the diverse natural population (not only a subset with specific virulence markers), 2) a genetic typing scheme that includes known and putative virulence genes and allows the detection of virulence gene transfer within the population, and 3) it includes a characterization of functional virulence that will be overlaid upon the molecular typing scheme. We have two specific aims that address the following questions: Do environmental factors influence the virulence potential of natural Vp populations in oysters? What is the genetic structure of northern Vp populations and how are pathogenic elements linked to this structure? PUBLIC HEALTH RELEVANCE: Recent major outbreaks of Vibrio parahaemolyticus in cooler northern climes have been linked not to the pandemic clone, but to distinct resident bacteria of unique genetic composition, perhaps foreshadowing the increasing risk to human health due to global climate change. A major obstacle to assessing risk of infection and developing preventative protocols is a lack of understanding of what factors contribute to the emergence of virulent biovars within natural V. parahaemolyticus populations. The combined molecular typing and virulence assessment in the context of estuarine ecology will provide invaluable insight necessary to generate predictive models for this emerging pathogen.

描述（由申请人提供）：许多传染病是由非致病性物种中的少数菌株引起的，但驱动其出现的生态和群体遗传机制仍不清楚。鉴于许多与气候和土地利用变化有关的流行病的发生频率不断增加，了解这些动态尤为重要。例如，在美国大部分地区，受污染的贝类引起的疾病相对较少，但发病率正在上升，并开始与温暖国家的发病率持平。主要致病菌副溶血弧菌 (Vp) 的丰度与中等盐度的温暖水域呈正相关。然而，这些生态变量并不能充分预测 Vp 流行病，部分原因是潜在致病性 Vp 的相对丰度难以预测。该项目旨在确定和量化影响牡蛎中有毒 Vp 相对流行率的生态因素。我们的模型研究区域——新罕布什尔州大湾河口——是理想的选择，因为在相对较小的空间尺度上存在着广泛的环境条件，而且其温暖的水域促进了通常与温暖气候相关的物种的生长。已知 Vp 与其他致病性弧菌一起居住在该河口，并且该河口发生了数起急性 Vp 感染，表明少数致病菌株居住在该群落中。我们的焦点问题是：环境因素如何驱动Vp的种群动态？我们假设毒力特征不同的 Vp 菌株与某些环境变量相关，因此气候波动将特别影响毒力 Vp 的相对丰度。我们的这一假设基于我们的初步数据，该数据显示高细胞毒性菌株的流行与温度升高之间存在显着相关性。使用多位点序列分型分析（MLST），我们将检查河口分离株之间的种群结构和重组程度。到目前为止，我们的初步基因分型表明，具有三个不同 Vp 群体的群落内存在显着的基因交换。拟议的研究与已发表的研究相比是独一无二的，特别是 1) 包含了多样化的自然群体（不仅仅是具有特定毒力标记的子集），2) 包括已知和假定的毒力基因并允许检测毒力的基因分型方案群体内的基因转移，3) 它包括功能毒力的特征，该特征将覆盖在分子分型方案上。我们有两个具体目标来解决以下问题：环境因素是否影响牡蛎中天然 Vp 种群的毒力潜力？ 北方 Vp 群体的遗传结构是什么？致病因素如何与该结构相关？ 公共卫生相关性：最近在较凉爽的北方地区发生的副溶血性弧菌的重大爆发与大流行克隆无关，而是与具有独特遗传组成的不同常驻细菌有关，这或许预示着全球气候变化对人类健康造成的风险日益增加。评估感染风险和制定预防方案的一个主要障碍是缺乏对哪些因素导致副溶血性弧菌天然种群中出现剧毒生物变种的了解。河口生态背景下的分子分型和毒力评估相结合将为生成这种新兴病原体的预测模型提供宝贵的见解。