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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

    • the following information is not yet verified
      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 species present.

      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).

  • Gram stain

    • the following information is not yet verified
      Gram positive branching rods

  • Culture characteristics

    • the following information is not yet verified

      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

      Blood Agar
      The colonies have a rough (“molar tooth”) or smooth surface, not hemolytic

      Brucella Blood Agar 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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