Actinomycosis

Key Features

Essentials of Diagnosis

• History of 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

Diagnosis

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

Imaging Studies

• 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

Treatment

Medications

• 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

• Sulfonamides such as sulfamethoxazole may be an alternative regimen at ...