Exophiala dermatitidis has been isolated from plant debris and soil and is a recognised causative agent of mycetoma and phaeohyphomycosis in humans (Zeng et al. 2007).
Morphological Description: Colonies are slow growing, initially yeast-like and black, becoming suede-like, olivaceous-grey with the development of aerial mycelium with age. A brown pigment is often produced in the agar. The initial yeast-like phase is characterised by unicellular, ovoid to elliptical, budding yeast-like cells. The yeast-like cells are hyaline and thin-walled when young becoming darkly pigmented (dematiaceous) and thick-walled when mature. With the development of mycelium, flask-shaped to cylindrical annellides are produced. Conidia are hyaline to pale brown, one-celled, round to obovoid, 2-4 x 2.5-6 µm, smooth-walled and accumulate in slimy balls at the apices of the annellides or down their sides. Cultures grow at 42OC and on media containing 0.1% cycloheximide.
Molecular Identification: ITS and/or D1/D2 sequencing is recommended for species identification (Halliday et al. 2015).
References: de Hoog and Hermanides-Nijhof (1977), McGinnis (1980), Hohl et al. (1983), Nishimura and Miyaji (1983), Matsumoto et al. (1984), Dixon and Polak-Wyss (1991), de Hoog et al. (2000, 2015).
Phialides and conidia of Exophiala dermatitidis.