Actinomycosis

Actinomycosis is a rare, chronic, and often suppurative (pus-filled) infection disease caused by bacteria of the genus Actinomyces. This disease is typically characterized by the formation of masses, fistulas, and granulomas in the face, neck, chest, and abdominal regions. Actinomyces bacteria are normally commensal microorganisms found in the human body, particularly in the mouth, throat, and gastrointestinal tract. However, they can become pathogenic when mucosal barriers are disrupted or the immune system is compromised. Due to its slow progression and clinical features that may be confused with other infections, the diagnosis of actinomycosis is often delayed.

Etiology and Pathogenesis

The causative agents of actinomycosis, Actinomyces species, are Gram-positive, anaerobic or microaerophilic bacteria. The most commonly encountered species include A. israelii, A. gerencseriae, and A. odontolyticus. While these bacteria are harmless as part of the normal flora, they can become pathogenic following trauma or surgical intervention. In particular, the risk of infection increases after dental caries or periodontal disease.

In the development of the disease, the invasion of bacteria into tissues and the resulting granulomatous inflammatory response are critical. Characteristic lesions known as “sulfur granules” are observed in infected tissues.

Clinical Features and Classification

Actinomycosis is classified according to the site of infection:

• Cervicofacial Actinomycosis: The most common form. Following dental infections, it may present with swelling and pain in the face and neck, fistulas, and trismus.
• Thoracic Actinomycosis: Involves the lungs and may develop following aspiration.
• Abdominal Actinomycosis: Occurs after gastrointestinal perforation. It presents with abdominal pain, weight loss, and fistulas.
• Pelvic Actinomycosis: Associated with long-term intrauterine device use. Symptoms include pelvic pain and vaginal discharge.
• Rare Forms: May involve the central nervous system or skin.

Diagnosis

In addition to clinical findings, the following are used for diagnosis:

• Histopathology: Sulfur granules support the diagnosis.
• Culture: The gold standard, although growth is difficult.
• Molecular methods (PCR): Used for species identification.

Treatment

• Antibiotics: Prolonged treatment is required. Penicillin is the first-line agent (6–12 months).
• Surgery: Interventions such as abscess drainage or fistula excision may be necessary.