Using Bioluminescent Salmonella to Identify Infection Sites Contributing to Contamination of Ground Turkey Meat

Poultry products are the most frequently implicated sources of human Salmonella infections in the U.S. with estimated 1.2 million illnesses and 450 deaths per year, and total combined costs due to foodborne Salmonella exceeding $2.7 billion annually. A better understanding on the dynamics of Salmonella infection in poultry is important in order to design control measures and intervention strategies to prevent foodborne illnesses. The overall goal of this proposal is to reveal harborage sites in turkeys following Salmonella infection as a source of contamination in ground poultry products. The objectives of this proposal are: (1) to determine the dynamics of Salmonella Typhimurium and S. Heidelberg colonization and clearance from tissues during systemic infection in turkeys and (2) to determine the Salmonella harborage sites in ground product components (skin, feather follicles, lymphatics, skeletal muscle and bone) and the ability of Salmonella to localize in microscopic lymphoid tissue and feather follicles. Investigators will use a bioluminescence imaging (BLI) system to detect bioluminescent Salmonella in order to visualize infected tissues and to monitor Salmonella dissemination over time. Bioluminescence in colonized tissues will be quantified by computer analysis of emitted photons and correlated with detectable colony forming units recovered from infected tissues that luminesce. Investigators will also determine the Salmonella cell tropism in colonized tissues by immunohistochemistry.

S. Typhimurium, S. Enteritidis and S. Heidelberg are the top serovars linked to foodborne salmonellosis worldwide. Although numerous measures have been implemented to minimize surface contamination in poultry carcasses during processing, Salmonella are still frequently recovered from ground products. If systemic infection is responsible for Salmonella contamination in finished ground products, the identification of Salmonella harborage sites and the removal of these sites during processing may be the solution to prevent outbreaks of foodborne salmonellosis. Previous studies on Salmonella pathogenesis in poultry species were limited to in vitro assays and enumeration of recovered bacteria from tissues. The present research is unique because investigators will use a highly sensitive BLI system to monitor specific body sites infected with Salmonella and the dynamics of Salmonella colonization and clearance from these sites over time. The present proposal will explore the concept of "internalized" Salmonella contamination in ground poultry components and the role of lymphoid tissue as harborage sites for this pathogen as requested by the Foundation. The results obtained from this research have the potential to improve food safety by changing current Salmonella control programs during poultry meat processing. Additionally, BLI technology may potentially be used in future to determine the efficacy of Salmonella vaccines, probiotics and antibiotic therapy in the prevention of Salmonella colonization and systemic dissemination in chickens and turkeys.