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For further information, see CMDT Part 33-32: Actinomycosis

Key Features

Essentials of Diagnosis

  • Recent dental infection, abdominal trauma, or intrauterine contraception device placement

  • Chronic pneumonia or indolent cervicofacial or intra-abdominal abscess

  • Sinus tract formation

General Considerations

  • Organisms are anaerobic, gram-positive, branching filamentous bacteria (1 mcm in diameter) that may fragment into bacillary forms

  • Occur in the normal flora of the mouth and tonsillar crypts

  • When introduced into traumatized tissue and associated with other anaerobic bacteria, actinomycetes become pathogens

  • Most common site of infection is cervicofacial area (about 60% of cases)

  • Infection typically follows extraction of a tooth or other trauma

  • Lesions may develop in the gastrointestinal tract or lungs following ingestion or aspiration of the organism from its endogenous source in the mouth

Clinical Findings

Symptoms and Signs

Cervicofacial actinomycosis

  • Develops slowly, becomes markedly indurated, and the overlying skin becomes reddish or cyanotic

  • Abscesses eventually drain to the surface

  • Persist for long periods

  • Sulfur granules—masses of filamentous organisms—may be found in the pus

  • There is usually little pain unless there is secondary infection

Thoracic actinomycosis

  • Fever, cough, sputum production

  • Night sweats, weight loss

  • Pleuritic pain

  • Multiple sinuses may extend through the chest wall to the heart or abdomen

Abdominal actinomycosis

  • Pain in the ileocecal region

  • Spiking fever and chills

  • Vomiting

  • Weight loss

  • Irregular abdominal masses may be palpated

  • Pelvic inflammatory disease caused by actinomycetes has been associated with prolonged use of an intrauterine contraceptive device

  • Sinuses draining to the exterior may develop

Differential Diagnosis

  • Lung cancer

  • Tuberculous lymphadenitis (scrofula)

  • Other cause of cervical lymphadenopathy

  • Nocardiosis

  • Crohn disease

  • Pelvic inflammatory disease from another cause


Laboratory Tests

  • Organisms may be demonstrated as a granule or as scattered branching gram-positive filaments in the pus

  • Anaerobic culture is necessary to distinguish from Nocardia

  • Histopathology exam of affected tissue and bone is useful in identifying organisms, which are fastidious and slow to culture


  • Chest radiograph shows areas of consolidation and, in many cases, pleural effusion

  • Abdominal pelvic CT scanning reveals an inflammatory mass that may extend to involve bone



  • Penicillin G

    • Drug of choice

    • 10–20 million units intravenously for 4–6 weeks followed by penicillin V, 500 mg four times daily orally

  • Alternatives include

    • Ampicillin, 12 g/day intravenously for 4–6 weeks, followed by amoxicillin, 500 mg three times daily orally or

    • Doxycycline, 100 mg twice daily intravenously or orally

  • Therapy should be continued for weeks to months after clinical manifestations have disappeared ...

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