DESCRIPTIONS OF MEDICAL FUNGI

Descriptions of Medical Fungi 89
Exophiala spinifera complex
Synonymy: Phialophora spinifera Nielsen & Conant
Rhinocladiella spinifera (Nielsen & Conant) de Hoog
E. spinifera has a worldwide distribution and is a recognised causative agent of
mycetoma and phaeohyphomycosis in humans. Zeng et al. (2007) presented an
overview of the medically important Exophiala species.
Recent molecular studies have re-examined Exophiala spinifera and have recognised
two species: E. spinifera and E. attenuata (Vitale and de Hoog, 2002). These two
species are morphologically very similar and can best be distinguished by genetic
analysis.
Molecular Identification: ITS sequencing is recommended for accurate species
identification (Zeng and de Hoog, 2008).
Morphological Description: Conidiogenous cells are predominately annellidic and
erect, multicellular conidiophores that are darker than the supporting hyphae are
present. No growth at 40 O C.
E. spinifera Annellated zones are long with clearly visible, frilled annellations.
E. attenuata Annellated zones are inconspicuous and degenerate.
RG-2 organism.
Exophiala spinifera (Nielsen & Conant) McGinnis
Morphological Description: Colonies are initially mucoid and yeast-like, black,
becoming raised and developing tufts of aerial mycelium with age, finally becoming
suede-like to downy in texture. Reverse is olivaceous-black. Conidiophores are
simple or branched, erect or sub-erect, spine-like with rather thick brown pigmented
walls. Conidia are formed in basipetal succession on lateral pegs either arising
apically or laterally at right or acute angles from the spine-like conidiophores or from
undifferentiated hyphae. Conidiogenous pegs are 1-3 µm long, slightly tapering and
imperceptibly annellate. Conidia are one-celled, subhyaline, smooth, thin-walled, subglobose
to ellipsoidal, 1.0-2.9 x 1.8-2.5 µm, and aggregate in clusters at the tip of each
annellide. Toruloid hyphae and yeast-like cells with secondary conidia are typically
present.
Note: Yeast cells show the presence of capsules in India Ink stained mounts and
cultures will grow on media containing 0.1% cycloheximide. No growth at 40 O C.
References: de Hoog and Hermanides-Nijhof (1977), McGinnis and Padhye (1977),
Domsch et al. (1980), McGinnis (1980), Nishimura and Miyaji (1983), de Hoog (1985),
Matsumoto et al. (1987), Dixon and Polak-Wyss (1991), de Hoog et al. (2000, 2003,
2006, 2015).