Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 3/28/2008
Publication Date: 2/1/2010
Citation: Bearson, S.M., Bearson, B.L. 2010. Traversing the Swine Gastrointestinal Tract: Salmonella Survival and Pathogenesis. In: Ricke, S.C., Jones, F.T., editors. Perspectives on Food-Safety Issues of Animal-Derived Foods. Fayetteville, AR: University of Arkansas Press. p. 35-48.
Technical Abstract: As the most consumed meat in the world, pork has been attributed to an estimated 14.6% of known causes of foodborne illnesses. The presence of the foodborne pathogen Salmonella in swine is both a food safety issue and animal health concern, costing pork producers over 100 million dollars annually. The estimated prevalence of Salmonella in swine is 6-8%, and 38-58% of swine operations tested positive for Salmonella based on the National Animal Health Monitoring System (NAHMS) 2000 report and the Collaboration in Animal Health and Food Safety Epidemiology (CAHFSE) 2005 report. Of the 10 most frequently identified Salmonella serovars from shedding hogs in the NAHMS study, 4 were also on the CDC’s top ten list of Salmonella serovars isolated from humans (Typhimurium, Enteritidis, Agona, and Heidelberg). Both the national Hazard Analysis Critical Control Point (HACCP) program for slaughter plants as well as consumer education on proper handling and cooking of raw meat are important to reduce the incidence of Salmonella exposure in pork. However, pork consumption is not the only possible culprit for foodborne outbreaks; Salmonella-contaminated pig manure used as fertilizer on crops that may be eaten raw by the consumer (i.e. fruits and vegetables) or that may run-off into our water supplies emphasizes the importance of pre-harvest food safety at the farm. Both clinically and sub-clinically (carrier) infected pigs can shed Salmonella. As a result of their rooting behavior, the fecal-oral route is the most common route of Salmonella infection. Thus, a major source of Salmonella infection to a pig is another pig. Following ingestion of Salmonella by the pig, the pathogen must survive the volatile conditions of the stomach, compete with the resident gut microbiota, invade the intestinal epithelial lining, and evade as well as manipulate the host’s immune system to achieve colonization. Hence, many attributes contribute to the pathogenesis of Salmonella in swine. Although Salmonella has been extensively studied over several decades in the mouse model, investigations at the molecular level of the virulence mechanisms employed by Salmonella in the pig and the porcine response to infection are limited. This chapter will specifically discuss Salmonella infections in swine, focusing on the molecular mechanisms known to date that are involved in Salmonella virulence and the porcine response.