Food Safety Microbiology and Foods for Health

NON-TECHNICAL SUMMARY: Foodborne illness sickens more than 70 million people per year in the United States. Food safety is important to everyone and is among California's and the U. S.'s top agricultural priorities. Food is by definition the product of agriculture consumed by humans. It is expected that food is to be safe of harmful microorganisms and contribute to the health of the individual. While U. S. citizens enjoy having an exceptionally safe and nutritious food supply there are occasions where food becomes contaminated with pathogens (bacteria, viruses and parasites) that result in human infections. These infections, in severe cases, lead to unnecessary mortality. By completing fundamental and applied research there is a basis of scientific knowledge on which to rationally design methodologies and standards to continually improve food safety.

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APPROACH: 1. Biofilms - Evaluation of Sat function will be done by using molecular genetics to generate a L. monocytogenes mutant defective for Sat. The mutant will be generated by constructing a deletion mutation of lmo1068 (which encodes Sat) using a PCR based methodology. This allele will then be introduced into the L. monocytogenes chromosome by allelic exchange. The Sat mutant will be evaluated using both the static biofilm assay and also using a flow cell apparatus. In addition, Sat will be purified and the ability of this protein to promote surface attachment will be determined. <P> 2. Bacterial survival on food - To develop a model system for internalizing bacteria, we will use molecular genetics to generate strains of foodborne pathogens that are bioluminescent. We will begin with E. coli O157:H7 as the species of interest since it has been a frequent cause of illness from consumption of leafy-greens. The model infiltration system will take advantage of the natural capacity of plant xylem tissue to conduct fluid movement powered through transpiration. Bacteria will be introduced into the xylem vasculature at a cut edge located near the based of a leaf (Romaine lettuce). Subsequently, the efficacy of washing with acetic acid, lactic acid and chlorine-based solutions. To accomplish this, infiltrated leaves will be soaked in the wash solutions for define periods of time, then the survival of bacteria at different site within the leaf will be measured. <P> Causes of foodborne illness - To begin to understand how factors injected into human cells alter an infection, it is necessary to define their mechanism of action. To this end, we are focusing our work on a group of injected Y. enterocolitica factors calls Ysps. There are eight Ysps and each will be studied separately. In each case, we will use molecular biology and cell biology approached such as yeast-two hybrid analysis and fluorescent microscopy to define the cellular target of a Ysp. Once we know this information, then we will test hypotheses to evaluate how and define how the Ysp alters the function of the cell. <P>Health and protection from foodborne illness - Evaluation of prebiotics and probiotics requires rigorous assessments along with studies that allow for insight on the mechanisms that drive positive outcomes. The mouse model of human foodborne illness presents an excellent surrogate to human studies. This model has been used extensively for defining how foodborne pathogens like Salmonella cause disease. In this study, mice will be placed on a diet that includes MO with and without Bifidobacteria. The microbial consortium of the intestine will be surveyed to define how these two dietary factors affect the flora of the intestinal tract. Mice with these various diets will also be challenged with Salmonella typhimurium to assess their susceptibility to foodborne infection.