• Bimodal Age Distribution: 11-20 y/o and 30-60 y/o (but can occur at any age)
  • Sex: M/F ratio: 4:1
  • Occurs in immune competent hosts (no increased risk in immunocompromised hosts)

Predisposing Factors

  • Aspiration of Oral Contents
  • Periodontitis/Poor Oral Hygiene
  • COPD
  • Bronchiectasis
  • Facial/Chest Wall Trauma
  • ETOH Abuse


(these organisms are normal oropharyngeal commensals)

  • Actinomyces israelii
    • Actinomyces is Gram-positive diphtheroidal or filamentous branching rods
  • Arachnia (Proprionibacterium) proprionicum
  • Associated Infectious Agents (Actinomycosis is classically a mixed infection):
    • Actinobacillus (Haemophilus) actinomycetemcomitans
    • Bacteroides


  • Infection of lung parenchyma with suppurative or granulomatous inflammation
    • Infection may extend contiguously to pleural space and chest wall



  • Leukocytosis is usually absent
  • Anemia may be severe

Pleural Fluid

  • May appear as frank pus with PMN-predominance or serous fluid with lypmphocyte-predominance
  • “Sulfur Granules” (2 mm yellow granules): may be seen in the pus from chest wall tracts (may filter pus to obtain granules, then crush and stain)
  • Gram Stain: matted mass of gram-positive diphtheroidal or filamentous branching rods in a sulfur granule
  • Anaerobic Cultures: positive for Actinomyces israelii in <50% of cases (usually necessitating biopsy to make the diagnosis)

CXR/Chest CT Patterns

  • Localized Infiltrate Extending to Chest Wall with Pleural Thickening or Effusion: characteristic appearance
    • May cross interlobar fissures
    • May have associated bone or chest wall destruction
  • Solitary Nodule: less common
  • Fibrocavitary Infiltrate: less common
  • Massive Empyema: less common

Sputum c/s

  • May demonstrate “sulfur granules” (rarely)
  • Recovery of organism from sputum is not useful (due to oropharyngeal colonization)

FOB with Transbronchial Bx

  • May recover organism

Transthoracic Needle Aspirate

  • May recover organism

Clinical Presentations

Thoracic Actinomycosis (15% of cases)

(usually insidious onset over weeks-months)

  • Constitutional Symptoms
    • Fatigue
    • Weight loss
    • Low-grade fever
  • Pneumonia/Necrotizing Pneumonia (see Pneumonia, [[Pneumonia]] and Necrotizing Pneumonia, [[Necrotizing Pneumonia]])
    • Dyspnea
    • Productive Cough: putrid sputum and hemoptysis are unusual
    • Local rales
    • Decreased breath sounds
    • Pleuritic Chest Pain:
  • Pleural Effusion/Empyema (see Pleural Effusion-Exudate, [[Pleural Effusion-Exudate]]): >50% of cases have pleural involvement
  • Chest Wall Abscess/Draining Chest Wall Sinus Tract/Local Chest Wall or Bone Destruction
  • Mediastinitis
  • Pericarditis
  • Vertebral Osteomyelitis (see [[Osteomyelitis]])
  • Disseminated Actinomycosis
    • More common with pulmonary Actinomycosis
    • May disseminate to brain/bones/skin

Ileocecal Actinomycosis (20-25% of cases)

  • xxx

Cervicofacial Actinomycosis (50-60% of cases)

  • Rarely coexists with thoracic disease
  • Facial Nodules (“Lumpy Jaw”)


  • Preferred Regimen: high dose IV Penicillin (12-20 million units/day) x 4-6 weeks), then at least 6 months of PO Penicillin (or Ampicillin)
  • May need to add agents for other coexistent organisms (addition of ß-lactamase inhibitor, if ß-lactamase-positive anaerobes are also present, etc.)
  • Alternative Agents:
    • Clindamycin: may occasionally fail if Actinobacillus is also present
    • Erythromycin
    • Doxycycline
  • Surgery: usually not necessary
    • May be necessary for drainage of large empyema or for excision of a chest wall sinus tract


  • Death is rare with appropriate therapy


  • xxx