Aerogenous infection of microbiologically defined minipigs with Streptococcus suis serotype 2. A new model.

Streptococcus suis serotype 2 is the cause of serious infections in animals and humans, but certain aspects of the infection pathogenesis still remain unclear. In this study an experimental model of aerogenous infection and induction of septicemia with S. suis serotype 2 was established in microbiologically defined Göttingen minipigs. Ten animals were exposed to aerosolized S. suis after previous exposure to mild acetic acid in aerosol. Six of the animals were immunosuppressed with prednisolone acetate on different days. All the animals were monitored clinically until euthanasia on days 6 to 13 after exposure. Necropsy was performed and samples were taken for microbiology, histopathology, and immunohistochemistry Three out of four animals immunosuppressed on days 5 to 7 after exposure developed S. suis septicemia, and S. suis could be detected in the tonsil of the soft palate and/or the nasal cavity of all exposed animals. Thus, using the presented model, local as well as systemic infection with S. suis serotype 2 was established in the Göttingen minipig. Since this breed is defined as free of S. suis and a range of other endemic porcine pathogens, the experimental model could prove useful in the study of this infection.