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United States Department of Agriculture

Agricultural Research Service

Research Project: GENOMIC AND IMMUNOLOGICAL CHARACTERISTICS OF JOHNE'S DISEASE Title: Evaluation of the pathogenicity and virulence of three strains of Salmonella organisms in calves and pigs

Authors
item Xiong, Nalee -
item Brewer, Matt -
item Day, Tim -
item Kimber, Michael -
item Barnhill, Alison
item Carlson, Steve -

Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 13, 2009
Publication Date: October 1, 2010
Citation: Xiong, N., Brewer, M., Day, T.A., Kimber, M.J., Barnhill, A.E., Carlson, S.A. 2010. Evaluation of the pathogenicity and virulence of three strains of Salmonella organisms in calves and pigs. American Journal of Veterinary Research. 71(10):1170-1177.

Interpretive Summary: Using swine as a host, the disease-causing abilities of three strains of Salmonella capable of causing unusual Salmonella infections in cattle were assessed. Thirty-six Holstein calves and 72 pigs experimentally infected with Salmonella were used. Three new Salmonella disease outcomes have been characterized in cattle over the last ten years. Representative Salmonella strains were orally inoculated into swine and clinical signs were compared to that observed in cattle. Samples were collected from various tissues and the presence of Salmonella was measured. Of the three unique Salmonella infections observed in cattle, only one was observed in swine. This type of Salmonella infection was exacerbated by free-living protozoa that can be found in swines’ drinking water. In this study, intensified Salmonella infection was identified in swine infected with antibiotic-resistant GI1-bearing strains exposed to free-living protozoa. Therefore, it appears that protozoa-associated Salmonella infection is analogous in swine and cattle.

Technical Abstract: Objective—Using swine as a host, to assess the pathogenicity and virulence of three strains of Salmonella capable of causing atypical salmonelloses in cattle. Animals—36 Holstein calves and 72 pigs experimentally infected with Salmonella spp. Procedures—Three new Salmonella disease phenotypes (protozoa-mediated hypervirulence, multisystemic cytopathicity, and encephalopathy) have been characterized in cattle over the last ten years. Representative Salmonella strains were orally inoculated into swine and clinical manifestations were compared to that observed in cattle. Samples were collected from various tissues and the presence of Salmonella was assessed qualitatively and quantitatively using Salmonella-selective media. Results—Of the three unique salmonelloses observed in cattle, only protozoa-mediated hypervirulence was observed in swine. Hypervirulence was related to a faster onset of disease and higher pathogen burden. This phenotype was observed in swine infected with multiresistant Salmonella enterica serotypes Typhimurium or Choleraesuis bearing the SGI1 integron. Conclusions and Clinical Relevance—In this study, Salmonella hypervirulence was identified in swine infected with SGI1-bearing strains exposed to free-living protozoa. Additionally, this is the first study to identify an SGI1-bearing strain of S. enterica serotype Choleraesuis displaying augmented virulence in swine. Therefore, it appears that protozoa-associated salmonellosis is analogous in swine and cattle. Salmonella-mediated encephalopathy and multisystemic cytopathicity do not appear to be relevant in swine.

Last Modified: 4/21/2014
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