Response of Verocytotoxin-producing Escherichia coli to environmental stresses in food supply systems

产胞毒大肠杆菌（VTEC）是食源性微生物，能够引起出血性腹泻、溶血性尿毒症综合征（HUS）和死亡；因此，它们是一个严重的公共卫生问题。尽管O157:H7是最著名和研究最多的VTEC血清型，但人们对出现200多种高毒力的非O157产肠毒素大肠杆菌血清型日益感到关切，其中一些与食源性暴发和/或严重的人类疾病有关。了解VTEC如何适应食品和食品加工程序是防止VTEC在整个食品供应链中传播的关键。然而，VTEC是一组极其异质的生物，在许多食品和食品加工环境中的流行率和持久性差异很大。目前关于VTEC对若干不同的环境压力作出反应的能力的遗传基础的资料有限。我的研究项目的总体目标是更好地理解VTEC如何对食品和食品加工环境中存在的特定的、明确的压力做出反应。我假设，对这些细菌生物学的基本了解可以导致有针对性的缓解策略。我的五年研究计划旨在确定在暴露于(i)通常与食品加工相关的压力（即卫生，抗菌处理和热处理）和（ii）通常与VTEC感染相关的主要食品运输工具（即新鲜农产品和碎牛肉）中的VTEC存活期间有助于VTEC存活的重要遗传因素。我将测试从加拿大和美国的环境中分离出的多种VTEC菌株，散发疾病和爆发分离的VTEC菌株，以测试其在食品中的生存和生长潜力以及对食品加工程序的反应。此外，我将与训练有素的HQP一起使用转录组学（qPCR和RNASeq）和诱变（转座子诱变和靶向基因缺失）方法来识别和表征VTEC依赖于对环境胁迫做出反应的遗传因素。这些研究将解决VTEC的应激反应和环境适应的基本问题，为VTEC如何在食品和相关食品加工环境中生存提供新的知识。由于我调查的三分之二以上的VTEC菌株是在加拿大分离出来的，我的研究将为加拿大目前与VTEC相关的食品安全问题提供独特的见解。总的来说，我的研究项目的结果将成为制定VTEC相关食源性疾病监测和缓解战略的重要一步。HQP的培训将是我研究项目的另一个重要成果。

Verocytotoxin-producing Escherichia coli (VTEC) are foodborne microorganisms capable of causing bloody diarrhea, hemolytic uremic syndrome (HUS) and deaths; thus they represent a serious public health concern. Although O157:H7 is the best known and studied VTEC serotype, there is growing concern over the emergence of more than 200 highly virulent non-O157 STEC serotypes, several of which are associated with foodborne outbreaks and/or severe human illness. Understanding how VTEC adapt to foods and food processing procedures is a key to prevent VTEC transmission throughout the food supply chain. However, VTEC are an extremely heterogeneous group of organisms that vary significantly in prevalence and persistence in many foods and food processing environments. There is currently limited information on the genetic basis of the ability of VTEC to respond to a number of distinct environmental stresses. The overall goal of my research program will be to better understand how VTEC respond to specific, defined stresses present in foods and also food processing environments. I hypothesize that a fundamental understanding of the biology of these bacteria can lead to targeted mitigation strategies. My five-year research program aims to identify important genetic factors that contribute to VTEC survival during the exposure to (i) stresses commonly associated with food processing (i.e., sanitation, antimicrobial treatment and heat treatment) and (ii) storage in major food vehicles that are commonly associated with VTEC infections (i.e., fresh produce and ground beef). I will test a diversified panel of VTEC strains isolated from the environment, sporadic illness, and outbreak isolates in Canada and the USA for both survival and growth potential in foods and in response to food- processing procedures. Furthermore, I, along with trained HQP will use transcriptomics (qPCR and RNASeq) and mutagenesis (transposon mutagenesis and targeted gene deletion) approaches to identify and characterize the genetic factors that VTEC rely on to respond to the environmental stresses. These studies will address fundamental questions of stress response and environmental adaptation of VTEC which should provide new knowledge on how VTEC survive in foods and associated food processing environments. As more than two-thirds of the VTEC strains I investigate were isolated in Canada, my research will provide unique insights into the VTEC related food safety issues present in Canada. Overall, the results from my research program will serve as an important step towards the development of surveillance and mitigation strategies for VTEC associated foodborne diseases. Training of HQP will be another important outcome of my research program.