DESCRIPTIONS OF MEDICAL FUNGI

Descriptions of Medical Fungi 91
The genus Exserohilum contains about 35 species and may be differentiated from
the closely related genera Bipolaris and Dreschlera by forming conidia with a strongly
protruding truncate hilum (i.e. exserted hilum). In Drechslera species, the hilum does
not protrude; in Bipolaris species the hilum protrudes only slightly. Several species
of Exserohilum have been reported as agents of phaeohyphomycosis, notably E.
rostratum, E. mcginnisii and E. longirostratum. Although recent molecular studies have
demonstrated that the latter two species are probable synonyms of E. rostratum (de
Cunha et al. 2012b, Katragkou et al. 2014). E. rostratum was recently implicated in an
outbreak of fungal meningitis associated with contaminated methylprednisolone in the
United States.
RG-1 organism.
Exserohilum Leonard and Suggs
Exserohilum rostratum (Drechsler) Leonard & Suggs
Morphological Description: Colonies are grey to blackish-brown, suede-like to
floccose in texture and have an olivaceous-black reverse. Conidia are straight,
curved or slightly bent, ellipsoidal to fusiform and are formed apically through a pore
(poroconidia) on a sympodially elongating geniculate conidiophore. Conidia have a
strongly protruding, truncate hilum and the septum above the hilum is usually thickened
and dark, with the end cells often paler than other cells, walls often finely roughed.
Conidial germination is bipolar.
Key Features: Dematiaceous hyphomycete producing sympodial, transverse septate,
ellipsoidal to fusiform conidia with dark bands on both ends and a strongly protruding,
truncate hilum.
Molecular Identification: ITS and D1/D2 sequencing is recommended.
References: Domsch et al. (1980), Alcorn (1983), Adam et al. (1986), McGinnis et al.
(1986b), Rippon (1988), Burges et al. (1987), Dixon and Polak-Wyss (1991), de Hoog
et al. (2000, 2015), de Cunha et al. (2012b), Katragkou et al. (2014).
Antifungal Susceptibility: E. rostratum limited data (Australian National data); MIC
µg/mL.
No. 64
AmB 8 4 2 2
VORI 8 1 1 6
POSA 6 5 1
ITRA 8 4 4
E. rostratum data from 34 isolates (da Cunha et al. 2012); MIC µg/mL.
AmB Range