Actinomyces israelii

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Gram stain Culture

Colony of Actinomyces within an abscess.
A Gram stain is needed to see the filamentous organisms.
Large colonies of Actinomyces can appear macroscopically as yellow granules whch have been termed "sulfur granules".
The darkly staining eosinophilic rim at the periphery of the colonly consists of immunoglobulin and cell debris which is referred to as the Splendore-Hoeppli phenomenon.
This deposition occurs around colonies of fungi and bacteria and around parasitic organisms

Author: Yale Rosen / Wikimedia Commons

https://commons.wikimedia.org/wiki/File:Actinomycosis_2.jpg

Actinomyces israelii

General information
- Taxonomy
  Family: Actinomycetaceae
  
  Natural habitats
  This bacteria is a natural component of the human gastrointestinal and oral flora
  
  Clinical significance
  Altough they are not normally a disease causing organism, it is the primary causative agent of Actinomycosis, a long term infection that commonly affects the face and neck.
  
  They form the characteristic aggregates of branching bacilli seen macroscopically as "sulpher granules", there are always multiple polymicrobial 94.5%.
  
  Actinomycosis
  The disease is characterised by the formation of painful abscesses in the mouth, lungs or gastrointestinale tract.
  
  Actinomycosis abscesses grow larger as the disease progresses, often over months.
  
  The abscesses often contains characteristic granules (sulphur granules).
Diseases
- Actinomycosis
Gram stain
- Gram positive branching rods
Culture characteristics
- Anaerobic to microaerophilic
  
  They grow better anaerobic than aerobic, or grow poorly or not at all aerobic, but after a number of subcultures they grow aerobically / CO2
  
  BA: colonies have a rough (“molar tooth”) or smooth surface, not hemolytic
  
  BBA Ø:
  - rough colonies: young (2-3 days old) growing like spider shaped colonies they grow a typical shape of a “molar tooth” or “breadcrumb”, often sandy (gritty), hard and stick to the agar (7-14 days), non-hemolytic
  
  - smooth colonies: are slightly elevated, white crème, and opaque
  
  Approximately one third of the strains are smooth and grow faster. In 2-3 days they are 1-2 mm.
  
  Older colonies can become pink
Characteristics
References
- James Versalovic et al.(2011) Manual of Clinical Microbiology 10th Edition

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