DESCRIPTIONS OF MEDICAL FUNGI

Descriptions of Medical Fungi 85
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).
RG-2 organism.
Exophiala dermatitidis (Kano) de Hoog
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 yeastlike
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 42 O C 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).
10 µm
Exophiala dermatitidis annellides and conidia.