These species are microaerophilic/anaerobic Gram positive rods, that can be part of the normal aspirated flora, especially with poor oral hygiene. Usually caused by Actinomyces israelii.

Clinical Manifestations

• Indolent, slowly progressive lesions
• Lung parenchymal lesions are associated with pleural infection leading to pleural thickening and empyema
  • Can be mistaken for lung cancer
  • The organism can break through fascial planes: spontaneous drainage of empyema through the chest
  • "sulfur granules" in purulent exudate represents clusters of branching Actinomyces filament
  • More common in alcoholics and those with poor dental hygeine

Diagnosis

• Gram stain -- branching forms, weakly gram positive
• Acid-fast stain negative
• Slow growth, minimum 5-7 days for identification

Treatment

1. IV PCN or ampicillin
2. followed by oral oral penicillin, amox, amox/clav for total duration of 6 month
3. Followup for at least 3 years due to high risk of recurrence