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

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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.