Anaerobic Gram-positive nonspore-forming bacilli:
>Actinomyces Led
>Bifidobacterium species


  • Genus of the actinobacteria class of bacteria.
  • Gram-positive, rod-shaped, non-spore-forming, non-acid-fast, facultative anaerobe.
  • Actinomyces are facultatively anaerobic (except A. meyeri, a strict anaerobe).
  • Actinomyces species do not form endospores
  • Actinomyces colonies form fungus-like branched networks of hyphae.
  • Actinomyces are known for causing disease in humans and are normally present in the gums and are the most common cause of infection in dental procedures and oral abscesses.
  • Many Actinomyces species are opportunistic pathogens particularly in the oral cavity.

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Important considerations:  The choice of an agent should be based on local antimicrobial sensitivities, site of infection, cost, and comorbid conditions.   Generally, the most common agents/regimens are listed first.    Listed dosages may need to be adjusted for renal dysfunction.

  1. Amoxicillin 500mg orally three times daily or Ampicillin 2 grams IVPB every 4-6 hours
  2. Penicillin G 2-4 million units IV q4-6h or Penicillin VK 500mg orally every 6 hours
  3. Clindamycin  600mg IV every 6 or 8 hours or 300mg orally four times daily 
  4. Doxycycline 100mg orally twice daily
  5. Erythromycin 500mg orally four times daily 
  6. Ceftriaxone 1-2 grams IV q24h
  7. Others