Actinomycosis in cats 

© Merck Veterinary Manual http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/50200.htm&word=actinomycosis

Actinomyces spp are normal flora of the oral and nasopharyngeal mucous membranes. Members of the genus Actinomyces are gram-positive, non-acid-fast rods, many of which are filamentous or branching. Branches are <1 µm in diameter, as opposed to fungal filaments, which are >1 µm in diameter. Several species are associated with diseases in animals.

A hordeovulneris causes localized abscesses and systemic infections, such as pleuritis, peritonitis, visceral abscesses, and septic arthritis in dogs. A common predisposing factor is the presence of tissue-migrating foxtail grass ( Hordeum spp ) particles. History and clinical signs may contribute to the diagnosis, but demonstration of the causative agent by Gram’s stain and bacteriologic culture is necessary for confirmation of etiology. Treatment includes surgical debridement and drainage and long-term treatment with penicillin or clindamycin.

A viscosus causes chronic pneumonia, pyothorax, and localized subcutaneous abscesses in dogs. Thoracic lesions are pyogranulomas, whereas cutaneous lesions are granulomatous abscesses, often with fistulous tracts. Lesions generally develop after a traumatic injury such as a bite wound. Diagnosis may be based on history and clinical signs, including the presence of soft, greyish white granules in the pus or exudate, and isolation and identification of A viscosus . Treatment of pyothorax with penicillin or clindamycin may be successful if begun early in the clinical course. A successful outcome is more likely with cutaneous infections, which should also be treated with the same antimicrobials.

Chronic ulcerative panniculitis in a cat with Actinomycosis