Salmonella Biomapping, Quantification, and Microbiome Exploration of Cull Hog Lymph Nodes and Tonsils to Assess Risk in Further Processed Pork Products Across the United States

Since the Meat and Meat Products Inspection Act of 1906, the pork industry has continued to improve production standards to provide a safe and accurately labeled product to consumers. The modernization of pork inspection has brought a new set of safety standards for the industry to uphold. Currently, pork is the most consumed meat product globally, and the United States alone produces and consumes pork and pork products at a rate that ranks third globally. Producing approximately 12.6 million metric tons annually, the U.S. ranks third globally in pork production behind only China and the European Union. As of 2024, the average American consumes an estimated 51 pounds of pork and pork products per year. However, these products account for a significant portion of foodborne illness cases annually. The CDC estimates that Salmonella causes 1.35 million infections, 26,500 hospitalizations, and 420 deaths in the United States annually. The USDA’s Food Safety Inspection Service (FSIS) estimates that pork and pork products are responsible for approximately 8-13% of these illnesses. Currently, the pork industry in the U.S. is implementing limited to no interventions to mitigate Salmonella in further processed pork products. In previous ICFIE laboratory research studies, it has been determined that there is an increase in Salmonella prevalence and indicator organism levels during the later stages of pork processing. Large-scale full-facility pork biomapping studies have indicated that lymph nodes in market hogs can serve as a reservoir for Salmonella in meat processing operations, increasing pathogenic prevalence in further processed products. However, potential Salmonella and the associated microbiome of the lymph nodes and tonsils of sows and boars has not yet been explored and can lead to potential contamination of the carcass and further processed pork products, as well as cross- contamination of the processing environment. With the implementation of New Swine Inspection Standards (NSIS), the industry will be expected to reduce the levels of Salmonella in pork trim and further processed products, such as ground sausage in order to meet the Healthy People 2030 Goals. The first chapter of this dissertation provides an overview of the history of meat processing and the pathogens associated with various pork products, specifically focused on Salmonella outbreaks in pork and how it relates to human illness, new swine inspection standards, current interventions in the pork industry to reduce pathogenic contamination, Salmonella presence in market hog lymph nodes, and the validation of testing methodologies for the quantification of Salmonella in pork products. Chapter 2 observes the baseline values of Salmonella prevalence and quantification in sow and boar lymph node varieties collected in the United States. Next, chapter three evaluated the comparison of Salmonella prevalence and quantification between market hogs and cull hogs. Finally, Chapter four explores a cross-comparison of the microbiome analysis of Salmonella-positive and negative lymph nodes and tonsils collected from cull hogs in the United States.