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The long term goal of this research is to reduce the incidence of food-borne illness and provide a safer food supply. To eliminate human bacterial pathogens, such as E. coli O157 and S. enterica, we will focus on multipliers, biotic and abiotic, that induce growth on fresh produce. Also, we will investigate the potential for agricultural inputs to act as a remedial measure for direct control of E. coli O157 and S. enterica.<P> The specific objectives are: <OL> <LI> To identify insects and associated damage which induce growth of E. coli O157 and S. enterica on leafy greens; <LI> To identify selected agricultural inputs which affect E. coli O157 and S. enterica on leafy greens; <LI> To identify plant survival factors among S. enterica serovars and pathogenic E. coli serotypes. </OL>The expected outputs will be conducting and analyzing experiments to meet the listed objectives. A graduate student will be mentored by the PI in experimental design and execution. Results from these studies will be presented at scientific conferences and symposia.
Non-Technical Summary: Life outside an animal model may be foreign to the study of human bacterial pathogens but the incidence of foodbourne illness caused by consumption of contaminated fresh produce is rising. Co-opting plants to vector itself may increase the competitiveness of Salmonella and pathogenic E. coli among the enteric pathogens by utilizing our industrial food chain to widely disperse itself from host to host. However, mystery surrounds this human pathogen-plant interaction in that Salmonella and pathogenic E. coli fail to grow on plants, but outbreaks continue to occur from consumption of fresh produce contaminated pre-harvest. This proposal focuses on identifying factors that lead to growth and thus, persistence of Salmonella and pathogenic E. coli in fresh produce. First, do common insects that feed on agricultural crops cause growth of Salmonella and pathogenic E. coli Do inputs administered by farmers to help the crop, actually, help these human pathogens Finally, do some pathogen strains carry unique genes which help these strains to colonize and persist in fresh produce Results from this project will be the basis for Best Management Practices with regard to food safety and insects and agricultural inputs. <P> Approach: Plant assays with E. coli O157:H7 and S. enterica will examine pathogen population dynamics on lettuce feed by different lifestages and population densities of thrips. Bacterial populations will be monitored and bacteria in planta will be visually examined by microscopy. We will expand the plant assays to include aphids. Identification of these interactions and whether the interaction is specific to an insect guild or common will highlight the significance of insects as a risk factor for E. coli O157:H7 and S. enterica survival and the likelihood of subsequent human disease. Next, common agricultural foliar inputs, such as fertilizers and pesticides, will be screened for E. coli O157:H7 and S. enterica growth. Finally, genetic differences among S. enterica serovars and E. coli serotypes will be examined for plant fitness phenotypes. Unique genes identified in the most fit serovar and serotype, but absent from the poor plant colonizers will be mutated and examined for a role in plant colonization. Understanding these mechanisms will point to strategies for reduction or elimination of produce contamination and incidence of human disease from produce-associated outbreaks.