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Unknown 18 = Exophiala dermatitidis
Colonies are slow growing, initially black and yeast-like, becoming suede-like, olivaceous grey and mould-like with age. Cultures grow at 42C.
Microscopy: An initial yeast-like phase is characterized by unicellular, ovoid to elliptical, budding yeast-like cells. With the development of mycelium, flask-shaped to cylindrical annellides are produced. Spherical phialides with large, fragile collarettes may also be present (not seen in this strain). Conidia are hyaline to pale brown, one-celled, round to obovoid, 2.0-4.0 x 2.5-6.0 um, smooth-walled and accumulate in slimy balls (glioconidia) at the apices of the phialides or down their sides.
The identity of this isolate was confirmed by sequencing the the D1/D2 region of large subunit rRNA. The strain showed >99.8% identity to numerous E. dermatitidis strains including strains from CBS while it only shows 97.5% ID to Exophiala jeanselmei.
Comment: Exophiala dermatitidis has been isolated from plant debris and soil and is a recognized causative agent of mycetoma and phaeohyphomycosis in humans. Clinical manifestations include subcutaneous cystic lesions, endocarditis and brain abscesses. E. dermatitidis is neurotropic and cerebral infections are frequently seen.
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