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The overall goal of this project is to identify and characterize bacterial determinants, food attributes, and environmental factors that affect the attachment, survival and persistence of Salmonella on the surface of different fruits and nuts in order to gain new knowledge regarding the physiology of this pathogen on such foods and to develop effective control measures to reduce its contamination. Specifically, we propose to use combined microscopic, microbiological, molecular and genomic approaches to study the physical and molecular mechanisms used by Salmonella outbreak serotypes and strains to attach to and survive on different produce items including tomato, cantaloupe, black pepper, almond and hazelnut under environmental conditions relevant to processing and storage. Different fruit and nut surface characteristics will be examined for the attachment behavior of Salmonella. A newly constructed library containing over 4,000 "barcoded" single-gene deletion mutants in Salmonella genomes will be used for systematic screening of additional genes required for Salmonella surface attachment.
<p>NON-TECHNICAL SUMMARY: <br/>Salmonella is the leading cause of hospitalizations and deaths due to known bacterial pathogens transmitted by food in the United States. In recent years, Salmonella has been frequently implicated in foodborne disease outbreaks associated with fruits, spices and nuts. The overall goal of this project is to identify and characterize bacterial determinants, food attributes, and environmental factors that affect the attachment, survival and persistence of Salmonella on the surface of different fruits and nuts in order to gain new knowledge regarding the physiology of this pathogen on such foods and to develop effective control measures to reduce its contamination. We will use combined microscopic, microbiological, molecular and genomic approaches to study the physical and molecular mechanisms used by Salmonella outbreak serotypes and strains to
attach to and survive on different produce items including tomato, cantaloupe, black pepper, almond and hazelnut under environmental conditions relevant to processing and storage. Different fruit and nut surface characteristics will be examined for the attachment behavior of Salmonella. A newly constructed library containing over 4,000 "barcoded" single-gene deletion mutants in Salmonella genomes will be used for systematic screening of additional genes required for Salmonella surface attachment. Results will be used for the development of knowledge-based intervention strategies that are effective and sustainable.
<p>APPROACH: <br/>Combined microscopic, microbiological, molecular and genomic approaches will be employed to study the physical and molecular mechanisms used by Salmonella outbreak strains to attach to and survive on different produce items including tomato, cantaloupe, black pepper, almond and hazelnut. Research will beconducted tobetter understand how Salmonella adapts to the environmental stresses (e.g. limited water and nutrients) commonly present on the fruit and nut surface and how such stresses influence Salmonella attachment and resistance to decontamination processes. Different fruit and nut surface characteristics (e.g. surface roughness and hydrophobicity) will bestudied to determine if they play a role in the attachment of Salmonella.Various environmental factors relevant to processing and storage (e.g. humidity and temperature) will be examined and relevant
processing techniques will be evaluated on Salmonella inactivation to identify effective hurdle strategies. Libraries of systematic single-gene deletion mutants in a Salmonella Typhimurium genome will be used with high-throughput Illumina sequencing technology to identify Salmonella genes important for produce surface attachment.