Actinomyces israelii

Actinomyces israelii

Background:

Actinomyces: 

• 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.

Actinomyces israelii:

• Gram-positive rod-shaped bacteria within the Actinomyces.
• Known to live commensally on and within humans (A. israelii is a normal colonizer of the vagina, colon, and mouth).
• Opportunistic pathogen and a cause of actinomycosis. Infection is established first by a breach of the mucosal barrier during various procedures (dental, GI), aspiration, or pathologies such as diverticulitis.
• Many physiologically diverse strains of the species are known to exist, though all are strict anaerobes.
• Manifestations of disease: Oral-cervicofacial disease is the most common form of actinomycosis.  Another form of actinomycosis is thoracic disease, which is often misdiagnosed as a neoplasm, as it forms a mass that extends to the chest wall.  Abdominal disease is another manifestation of actinomycosis. 
• Actinomycosis may be considered when a patient has chronic progression of disease across tissue planes that is mass-like at times, sinus tract development that may heal and recur, and refractory infection after a typical course of antibiotics.

Therapy:

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