Experimental actinomycosis caused by Actinomyces-like bacteria in mice anda sow

The present experiment was performed to test the pathogenicity of. actinomy ces-like bacteria in experimental animals and swine. Two rough (R) strains of Actinomyces-like bacteria isolated from a site of arthritis and from the tonsil in pigs were used as inocula. To investigate their susceptibility t o Actinomyces like bacteria, BALB/c, SS and ddY mice and guinea-pigs were i noculated intraperitoneally with the strains of. Actinomyces-like bacteria. The ddY mice were used for the long-term observation of Actinomyces-like b acteria lesions and the mammary tissue of a sow was inoculated with Actinom yces-like bacteria isolated from swine tonsil. Macroscopic observation reve aled many abscesses on the surfaces of the abdominal and/or thoracic organs in the mice, but not on those of the guinea-pigs. The sow del eloped firm nodules at the inoculation site in the mammary glands. Histopathologically, the lesions in the mice were characterized as actinomycotic abscesses in t he early stage and as pus-forming granuloma (PFG) in the advanced stage; th e lesions were accompanied by crystalloid particles. Actinomyces-like bacte ria induced granulomatous mastitis in die sow, and the lesion was character ized as PFG. The characteristic actinomycotic lesions in swine mammary glan ds were reproduced by experimental infection.