Identification of host-specific virulence determinants in the opportunistic enteric pathogen, Pantoea

机会性肠道病原体泛菌属宿主特异性毒力决定因素的鉴定

• 批准号: RGPIN-2015-06417
• 负责人: Stavrinides, John
• 金额: $ 2.48万
• 依托单位: University of Regina
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=665856
• 关键词: Identification; host; specific; virulence; determinants

Pantoea is a bacterial group that is closely related to human pathogenic, Enterobacter and E. coli, yet many isolates are currently registered in Canada as biological control agents for managing plant disease on crop plants. This is particularly concerning given that many Pantoea isolates have already been shown to cause plant disease themselves, as well as human disease. Pantoea has been noted to cause pulmonary infections, septicemia, and septic arthritis in both healthy and immunocompromised adults. The objective of this research program is to advance our understanding of the pathogenic ability of Pantoea, and more broadly, how pathogens adapt to exploit different hosts, including humans. This proposal rests on the hypothesis that there are specific disease determinants that enable Pantoea to cause disease in multiple hosts.***     The first objective is to identify candidate disease factors by comparing the genes of virulent and non-virulent isolates of Pantoea ananatis to identify those determinants that are present only in virulent isolates. To evaluate whether any of these genes are induced at human body temperature (37C), we will examine the expression of genes at 30C versus 37C using transcriptomic methods. The second objective is to evaluate whether genetic factors necessary for colonization of one host are needed for another host. This will be achieved using three mutant sets of P. ananatis, which were shown to be impaired in the ability to associate with either the fruit fly, nematode, or amoeba. Growth of the nematode and amoeba mutant sets will be evaluated in the model fruit fly to identify those genes that are specific to one host, or are needed for multiple hosts. The third objective will identify the genetic basis of hemolysin activity (lysis of red blood cells) exhibited by many Pantoea isolates at 37C. We will generate and screen mutant libraries for loss of hemolytic ability, thereby identifying the genes that are responsible for this capability. The fourth objective will evaluate the role of natural antibiotics produced by Pantoea during host association. Because hosts are often colonized by a variety of commensal bacteria, pathogens may enhance their ability to establish an infection by eliminating competing bacteria. Using fruit flies that are already infected with the pathogen Staphylococcus aureus, we will compare the colonization efficiency of an antibiotic-producing isolate to an antibiotic mutant to determine whether these natural products may be virulence factors that enhance host colonization.***     This research will identify virulence factors that contribute to the ability of Pantoea to cause disease in humans, and will allow us to assess the capacity for biological control strains to become pathogens. This research not only has broad implications for the regulation of biological control agents, but will also enhance our understanding of how bacteria evolve to become pathogenic.**

泛菌属是与人类致病菌肠杆菌属和大肠杆菌属关系密切的细菌类群。大肠杆菌，但许多分离物目前在加拿大注册作为生物控制剂，用于管理作物植物上的植物病害。 这一点尤其令人担忧，因为许多泛菌分离株已经被证明会导致植物疾病本身以及人类疾病。 泛菌已注意到导致肺部感染，败血症，脓毒性关节炎，在健康和免疫功能低下的成年人。 这项研究计划的目的是促进我们对泛菌属致病能力的理解，更广泛地说，病原体如何适应利用不同的宿主，包括人类。这一建议基于这样的假设，即存在特定的疾病决定因素，使泛菌能够在多个宿主中引起疾病。 第一个目标是通过比较菠萝泛菌的毒性和非毒性分离株的基因来确定候选疾病因子，以确定仅存在于毒性分离株中的那些决定因素。 为了评估这些基因中的任何一个是否在人体温度（37 ℃）下被诱导，我们将使用转录组学方法检测基因在30 ℃与37 ℃下的表达。第二个目标是评估一种宿主定殖所需的遗传因子是否也需要用于另一种宿主。 这将通过使用三组菠萝假单胞菌的突变体来实现，这些突变体显示与果蝇、线虫或变形虫相关联的能力受损。将在模型果蝇中评价线虫和变形虫突变体集的生长，以鉴定对一种宿主具有特异性或对多种宿主具有所需的那些基因。 第三个目标是确定许多泛菌属分离株在37 ℃下表现出溶血素活性（红细胞溶解）的遗传基础。我们将产生并筛选溶血能力丧失的突变体库，从而鉴定出导致这种能力的基因。第四个目标将评估泛菌产生的天然抗生素在宿主结合过程中的作用。由于宿主通常被各种肠道细菌定殖，病原体可以通过消除竞争细菌来增强它们建立感染的能力。使用已经感染病原体金黄色葡萄球菌的果蝇，我们将比较产生抗生素的分离株与抗生素突变体的定殖效率，以确定这些天然产物是否可能是增强宿主定殖的毒力因子。 这项研究将确定有助于泛菌引起人类疾病的毒力因子，并使我们能够评估生物控制菌株成为病原体的能力。 这项研究不仅对生物控制剂的调节具有广泛的意义，而且还将增强我们对细菌如何进化成为致病菌的理解。