Stress-Induced Resistance to High Pressure in Listeria monocytogenes and Escherichia coli O157:H7 (1998-02741)

High pressure processing is a novel, non-thermal technique for inactivating pathogens in food by the application of extremely high pressures. Application of pressures in the range of 5000-9000 atmospheres for 1-5 minutes, at room temperature, can significantly reduce the microbial population in food and dramatically extend its shelf life. Since heat is not used in the process, negligible flavor and nutrient changes occur as a result of the high pressure treatment. During the past two decades, new food-transmitted diseases emerged such as those caused by the enterohemorrhagic E. coli and the meningitis-causing Listeria. Such pathogenic bacteria are more likely to survive during food processing if they were exposed to conditions that make them resistant to preservation methods. For example, bacteria that are normally sensitive to heat may become heat-resistant when they are stressed during production, harvesting or even mild processing of food. Therefore, adaptation of bacteria to various stresses may compromise the safety of food. This challenge to the food industry needs urgent attention when new processing technologies (such high pressure processing) are introduced. This project will identify the potential causes for increased resistance of pathogens to pressure. Additionally, the study will assess, in quantitative terms, the relationship between stress that foodbome pathogens may encounter and resulting stress-induced resistance to high-pressure processing. The outcome of this project will help food manufacturers develop strategies to overcome and eliminate stress-adaptation in foodbome pathogens.