Experimental Salmonella typhi infection in the domestic pig, Sus scrofa domestica

The domestic pig, Sus scrofa domestica, was examined as a model for typhoid fever, a severe and systemic disease of humans caused by Salmonella typhi. Six pigs were inoculated 1 week post-weaning with approximately 10(10) col ony forming units (cfu) of wild type Salmonella typhi strain ISP1820 intran asally and observed for 3 weeks. S. typhi was cultured from the tonsils of 50% of the pigs at necropsy. Cultures from all other organs analysed (ileum , colon, spleen and liver) were negative. No clinical or histopathological signs of disease were observed. Pigs inoculated in parallel with swine-viru lent S. choleraesuis all exhibited signs of systemic salmonellosis indicati ng that the parameters of the experimental infection with S. typhi (e.g. ro ute) were appropriate. Whereas the pig has a gastrointestinal tract that is very similar to humans, our results indicated that the unique features of host and microbe interaction needed to produce typhoid fever were not mimic ked in swine. Nevertheless, our observation of tonsillar involvement was co nsistent with former observations of S. choleraesuis and S. typhimurium inf ections in swine and supports a role for the tonsil in all porcine salmonel la infections. (C) 2000 Academic Press.