Actinomycosis is a chronic granulomatous infection caused primarily by Actinomyces israelii, a gram-positive, anaerobic bacterium that normally resides in the oral cavity. The infection typically arises after mucosal disruption, leading to the formation of characteristic abscesses, sinus tracts, and sulfur granules in infected tissues. It often presents as a slowly progressive mass, commonly in the cervicofacial region. Unlike Nocardia or Bacillus anthracis, Actinomyces does not cause acute systemic illness but rather a localized indolent infection. Effective treatment requires prolonged high-dose penicillin therapy, often combined with surgical drainage of abscesses to remove fibrotic tissue and sinus tracts. Early recognition and management prevent extensive tissue destruction and complications.

Reference: Jawetz, Melnick & Adelberg’s Medical Microbiology, Murray et al, 28th Edition.