Identifying the Genetic Profile of the Salmonella-Carrier Pig to Improve Food Safety and Decrease Pre-Harvest Disease

Approach: Objective I - Experimentally infect pigs (n=40) with S. Typhimurium and quantitatively measure the fecal shedding at regular intervals (0 hrs, 48 hrs, 7 days, 14 days, 21 days). Animals with the lowest level of shedding at 21 days post infection (n=4, animals that showed infection but were culture negative for Salmonella after day 7) will be compared to animals with the highest shedding (n=6, animals that cultured positive for Salmonella at all time points including day 21) by using transcriptional profiling. RNA will be extracted from the mesenteric lymph nodes and blood of the 10 pigs, and transcriptional profiling will be accomplished through DNA microarray analysis (Affymetrix porcine chip) followed by quantitative real time PCR. <P>Objective II - Several methods (direct sequencing, PCR Restriction Fragment Length Polymorphism) analysis, and similar analyses) will be used to identify genotype and determine the frequency of DNA sequence variants (polymorphisms) in the challenge populations as well as commercial pig breeds. Such variants, termed DNA markers, may identify specific versions of genes (alleles) that are superior to other alleles of the gene in resisting disease.