Submitted to: International Symposium on the Epidemiology and Control of Foodborne Pathogens in Pork
Publication Type: Abstract only
Publication Acceptance Date: 8/25/2009
Publication Date: 9/30/2009
Citation: Rostagno, M.H., Eicher, S.D., Lay Jr, D.C. 2009. Experimental Salmonella Enterica Infection in Market-weight Pigs. International Symposium on the Epidemiology and Control of Foodborne Pathogens in Pork. Proceedings. Interpretive Summary:
Technical Abstract: Market pigs infected with Salmonella pose a significant food safety risk by carrying the pathogen into abattoirs. A study was conducted to determine the dynamic of Salmonella infection in market-weight pigs (220-240 lbs.). Pigs (n=24) were individually inoculated (intranasally; 108 cfu/mL) with Salmonella enterica serovar Typhimurium (a Nalidixic acid resistant strain). Fecal samples were collected from each pig, and 3 pigs were randomly selected and euthanized to collect additional samples (spleen, liver, mesenteric lymph node, ileal and cecal contents) on days 1, 2, 7, 14, 21, 28, 35, and 42 post-inoculation (p.i.). All samples were processed for the isolation and enumeration of the challenge strain used. No inoculated animal showed any clinical sign of the infection. Bacteriological data revealed that all inoculated pigs started shedding Salmonella within 24 h p.i., and persistently shed the bacteria up to the end of the study (i.e., 6 weeks). Ileal and cecal content samples were all positive throughout the study. Mesenteric lymph nodes were also positive during the entire study and at the same level as intestinal content samples. All samples contained 3-4 logs (cfu/g) of Salmonella at 24 h p.i., and 4-5 logs (cfu/g) of Salmonella up to 4 wk p.i. Interestingly, levels of Salmonella dropped markedly (P<0.05) in all samples at 5 wk p.i., being detectable only by bacteriological enrichment. Understanding the dynamic of Salmonella enterica infection in market-weight pigs will enable the pork industry to develop and plan the application of intervention strategies that will contribute to increased pork safety.