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- Sporotrichosis is caused by a complex of different species refered to as Sporotrhix schenckii complex, including:
- S. brasiliensis: Limited to South America, associated with cat transmitted disease
- S. globosa: Worldwide distribution, but most prevalent in East Asia. Infection associated with inoculation of contaminated plant matter
- S. schenckii (sensu stricto): World-wide distribution. Similar to S. globosa, infection is associated with inoculation of contaminated plant matter
- S. luriei: Limited to Africa and Asia. Less pathogenic than others
- Dimorphic fungi:
- Room temperature (25-28 C): Grow in filamentous form with septated hypha and conidia
- Body temperature (36-37 C): invasive, cigar shaped yeast 1-3 x 3-10 µm
- Exposure to the fungus: Multiple exposures and infections can arise from a single source
- Zoonotic (with S. brasiliensis): Infected cats can have high fungal burden and transmit S. brasiliensis via scratch or bite directly.
- Sapronotic (all non-brasiliensis Sporothrix species): Transmission is from contaminated plant matter or soil to people via minor cuts or scrapes.
- Testing exudate for presence of asteroid bodies (yeasts surrounded by immune material, Splendore–Hoeppli phenomenon) is a low cost and sensitive diagnostic method.
- Exudate material is placed on a slide with saline and a drop of 10% formaldehyde solution and examined by microscopy.
- Yeast phase [Fig 1]
- Fluorescent antibodies for tissue staining or culture confirmation [Fig 2].
- Histopathology: Important stains are PAS and Gomori-Grocott stains [Fig 3].
- Typical characteristics are yeast cells, asteroid bodies (although not pathognomonic for sporotrichosis)
- Histological patterns termed sporotrichoid, tuberculous and foreign body reactions.
- Culture of infected material (pus, secretions, tissues) is gold standard for diagnosis.
- Use Sabouraud dextrose at 28 C for 5-8 days to grow the filamentous form.
- Use blood chocolate, blood BHI agar at 37 C if want to grow the yeast form.
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