Epidemiology

• 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

Etiology

(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

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Physiology

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

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Diagnosis

CBC

• 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

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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”)

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Treatment

• 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

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Prognosis

• Death is rare with appropriate therapy

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References

• xxx