Submitted to: Veterinary Microbiology
Publication Type: Review Article
Publication Acceptance Date: 12/21/2010
Publication Date: 6/2/2011
Citation: Bearson, B.L., Bearson, S.M. 2011. Host specific differences alter the requirement for certain Salmonella genes during swine colonization. Veterinary Microbiology. 150:215-219.
Interpretive Summary: Salmonella enterica serovar Typhimurium is a bacteria that can cause food-borne disease in humans; however, it can often live in the gastrointestinal tract of pigs without causing illness in the pig. Hence, healthy pigs that carry Salmonella Typhimurium in their gastrointestinal tract can be a source of the disease-causing bacteria, threatening food safety and human health. Much of what we currently know concerning how Salmonella Typhimurium causes disease has been gained from studies in the mouse. Therefore, the development of methods including vaccines to reduce or prevent Salmonella Typhimurium in food-producing animals is frequently based on mouse studies. The disease caused by Salmonella Typhimurium in mice is usually severe and mice often die due to the illness; in contrast, disease in swine is usually mild (if any) and normal recovery is rapid. This leads to the question: do the differences in the severity of Salmonella Typhimurium illness comparing mice and pigs indicate that the methods to reduce disease in mice and pigs must also be different? Although many of the genes that are important for Salmonella Typhimurium to cause illness in mice are also required for causing illness in pigs, specific differences have been demonstrated. In fact, some live Salmonella Typhimurium vaccines that have been developed in the laboratory do not cause illness in mice, but do cause illness in pigs. The differences in Salmonella Typhimurium illness between pigs and mice emphasize the need to develop and evaluate methods to reduce Salmonella Typhimurium in swine, since the intervention will ultimately be used in food-producing animals such as pigs. This information is important for veterinarians and scientists in university, industry, and government sectors who develop methods to reduce food-borne bacteria during animal production.
Technical Abstract: The pathogenic potential of Salmonella is determined during the complex interaction between pathogen and host, requiring optimal regulation of multiple bacterial genetic systems within variable in vivo environments. The mouse model of systemic disease has been an extremely productive model to investigate the pathogenesis of Salmonella enterica serovar Typhimurium (S. Typhimurium). Although the mouse model is a widely-used paradigm for studying the pathogenesis of systemic disease caused by Salmonella, investigations concerning food safety interventions should employ natural hosts to examine gastrointestinal colonization by Salmonella. Recent research has demonstrated specific differences in the attenuation of certain S. Typhimurium mutants in mice compared to swine. This variation in pathogenesis between the mouse model and pigs for the S. Typhimurium mutants is presumably dependent upon either the requirements for specific gene products during systemic disease (mouse) versus gastrointestinal colonization (pig) or host specific differences. In addition, host specific diversity in Salmonella colonization of swine has also been described in comparison to other food producing animals, including cattle and chickens. Differences in Salmonella colonization and pathogenesis across diverse animal species highlight the importance of species-specific studies of gastrointestinal colonization for the development of Salmonella interventions to enhance pork safety.