Etiology

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Pathogen

• Actinomyces are primarily anaerobic, gram-positive, non-acid fast, branching, rod-shaped bacteria.

Predisposing factors

• Cervicofacial actinomycosis (most frequent form of actinomycosis)
  • Poor dental hygiene (e.g., dental caries)
  • Oral surgery (e.g., tooth extraction)
  • Maxillofacial trauma
  • Local tissue inflammation (e.g., tonsillitis, tumor)
  • Comorbidities (e.g., diabetes)
• Abdominal and pelvic actinomycosis
  • Intestinal surgery
  • Foreign body ingestion
  • Tumor
  • Ascending infection from the uterus, associated with intra-uterine contraceptive devices
• Thoracic actinomycosis
  • History of aspiration
  • Recent oral infection

Clinical features

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• Cervicofacial actinomycosis
  • Slowly progressive mass in the neck and/or face; most commonly in the mandible region
  • Usually painless nodular lesions
  • Becomes indurated with purulent discharge that contains sulfur granules from fistulae and draining sinus tracts.
    • Sulfur granules refer to macroscopic grains – approx. 1 mm in diameter – of hard clumps of bacterial filaments, pus, debris, and hyaline. The granules appear yellow within pus, although despite the name they do not contain sulfur.
• Thoracic actinomycosis
  • Cough, chest pain
  • Possible hemoptysis with yellow granules

Tip

Definitive diagnosis is based on the identification of actinomycotic sulfur granules or bacteria.

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The nonkeratinized, multilayered squamous epithelium of the oral mucosa can be seen (yellow overlay). There are multiple basophilic Actinomyces conglomerates (green overlays), which are surrounded by acute inflammatory cells (red hatched overlay). These conglomerates are palpable externally and visible macroscopically.

An aggregate of basophilic bacteria with radially branching filaments is visible at the center, which has a cauliflower-like appearance (yellow overlay).
The bacteria are surrounded by numerous granulocytes, resulting in a lesion with a rosette-like pattern (green overlay).

This is the typical histopathological appearance of a yellow “sulfur granule” caused by actinomycosis.