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Experimental actinomycosis caused by Actinomyces-like bacteria in mice and a sow
1Department of Animal Health, Tokyo University of Agriculture, Japan.
Abstract:
The present experiment was performed to test the pathogenicity of Actinomyces-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 to Actinomyces-like bacteria, BALB/c, SS and ddY mice and guinea-pigs were inoculated intraperitoneally with the strains of Actinomyces-like bacteria. The ddY mice were used for the long-term observation of Actinomyces-like bacteria lesions and the mammary tissue of a sow was inoculated with Actinomyces-like bacteria isolated from swine tonsil. Macroscopic observation revealed 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 developed firm nodules at the inoculation site in the mammary glands. Histopathologically, the lesions in the mice were characterized as actinomycotic abscesses in the early stage and as pus-forming granuloma (PFG) in the advanced stage; the lesions were accompanied by crystalloid particles. Actinomyces-like bacteria induced granulomatous mastitis in the sow, and the lesion was characterized as PFG. The characteristic actinomycotic lesions in swine mammary glands were reproduced by experimental infection.
Insights
This study demonstrates Actinomyces-like bacteria can cause abscesses and pus-forming granulomas in mice and mastitis in sows. These findings confirm the pathogenicity of these bacteria in experimental animals and swine.
Area of Science:
- Veterinary Pathology
- Microbiology
Background:
- Actinomyces-like bacteria are implicated in various infections.
- Understanding their pathogenicity in animal models is crucial for disease control.
Purpose of the Study:
- To evaluate the pathogenicity of Actinomyces-like bacteria in experimental animals and swine.
- To characterize the lesions induced by these bacteria.
Main Methods:
- Inoculation of Actinomyces-like bacteria (two rough strains) into BALB/c, SS, and ddY mice, and guinea pigs.
- Intraperitoneal inoculation in mice and guinea pigs; mammary gland inoculation in a sow.
- Macroscopic and histopathological examination of induced lesions.
Main Results:
- Mice developed abdominal and thoracic organ abscesses, progressing from actinomycotic abscesses to pus-forming granulomas (PFG) with crystalloid particles.
- Guinea pigs did not develop macroscopic lesions.
- The sow developed granulomatous mastitis characterized by PFG at the inoculation site.
Conclusions:
- Actinomyces-like bacteria are pathogenic, inducing characteristic actinomycotic lesions and PFG in mice.
- Experimental infection successfully reproduced actinomycotic lesions in swine mammary glands, confirming pathogenicity.