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Last updated: February 11, 2019


Actinomycosis is an infection caused by Actinomyces bacteria (especially Actinomyces israelii), which is ubiquitous in the oral cavity and is sometimes found in the gut or female genital tract. Actinomyces thrives in anaerobic environments, which are created by the proliferation of oxygen-consuming aerobic bacteria. The most frequent form of infection is cervicofacial actinomycosis, which occurs after injury to the oral cavity, face, or neck, although Actinomyces infection may also affect other parts of the body. The initial disease manifests as coarse, inflammatory nodules, which frequently develop into purulent, draining fistulae. Imaging enables a tentative diagnosis, but definitive diagnosis is based on culture and microscopic identification of Actinomyces. Antibiotics are used to treat actinomycosis and, in severe cases, surgery is required to remove lesions. Untreated cases of actinomycosis result in chronic, progressive disease.



Epidemiological data refers to the US, unless otherwise specified.



  • Actinomyces are primarily anaerobic, gram-positive, non-acid fast, branching, rod-shaped bacteria.
  • Actinomyces bacteria, particularly Actinomyces israelii, are found in the normal oral flora.

Predisposing factors

  • Poor dental hygiene, oral surgery (e.g., tooth extraction), local tissue inflammation (e.g., tonsillitis, tumor), comorbidities (e.g., diabetes) → cervicofacial actinomycosis
  • Intestinal surgery , foreign body ingestion, tumor → abdominal actinomycosis
  • Ascending infection from the uterus, associated with intra-uterine contraceptive devices → pelvic actinomycosis
  • History of aspiration, recent oral infection, or ongoing pulmonary malignancy (see aspiration pneumonia) → thoracic actinomycosis



Actinomyces is part of the normal flora of the oral cavity (less common in the lower gastrointestinal tract and female genital tract).

Actinomycosis infection spreads contiguously, with no regard for anatomical borders, and develops into multiple draining fistulae!


Clinical features

Cervicofacial actinomycosis (most frequent form of 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.

Abdominal and pelvic actinomycosis

  • Fever, abdominal discomfort, changes in bowel habits
  • Possible pathological vaginal bleeding or discharge

Thoracic actinomycosis



Suspected cases based on the clinical presentation (e.g., presence of sulfur granules) can be confirmed via identification of the organism from tissue specimen (e.g., pus, biopsy tissue from suspected lesion) or sulfur granules.

  • CT scan: assists in the identification of the exact location, extent of pathology, and/or guiding percutaneous aspiration of pus

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





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