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Actinomyces israelii

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Characteristics
- Gram-positive filamentous branching bacilli
- Grows slowly
- Anaerobic
Habitat
- Found as scanty normal commensal in the :
  - Mouth, especially anaerobic crevices around the teeth
  - Colon
  - Vagina
  - Disease begins when these normal flora enter adjacent sterile tissue e.g, by trauma, surgery
Transmission
- into tissues occurs during :
  - Dental extraction- poor dental hygiene
  - Trauma ( mouth - uterus)
  - Organism also aspirated into lungs, causing thoracic actinomycosis
Pathogenesis
- Infection occur in both :
  - Normal hosts
  - Immunocompromised patients
- Non toxins or virulence factor known
- Organism forms sinus tracts that open on yellow " sulfur granules "
  - sulfur granules : are made up of large masses of organisms microcolonies of filamentous bacteria
Disease
- Actinomycosis ( abscesses with draining sinus tracts )
- Chronic suppurative abscess
- The lesion ( Mycetoma ) :
  - Begins as a hard red swelling
  - Develops slowly, becomes filled with pus
  - Draining with sinus formation
- Sites
  - Oral- facial abscesses (>50% of cases ) - often associated with trauma or dental extraction
  - Abdominal infections: Abscess. Many after appendicitis
  - Uterine infection : Associated with intrauterine contraceptive devices
  - Chest infection
  - Invasive infection in immunocompromised patients
Laboratory Diagnosis
- Specimen: pus - Filaments may aggregate to form visible granules " Sulphur granules" in pus: Yellowish particles
- Microscopy: sulfur granules : Gram-positive filamentous, branching rods
- Culture: - Anaerobic culture on blood agar plate ( 10 days ) - Molar teeth colonies
- No serologic tests
Treatment
- Penicillin - For up to 3-12 months
- Tetracyclin or Clindamycin - For penicillin-allergic patients
- Surgical drainage
Prevention
- Good oral hygiene
- Prophylactic antibiotics in association with GIT or oral trauma or surgery
- No vaccine is available