DESCRIPTIONS OF MEDICAL FUNGI

Descriptions of Medical Fungi 179
Scedosporium Sacc. ex Castell. & Chalm.
The taxonomy of this genus has been subject to change on the basis of sequence data;
Scedosporium apiospermum and Scedosporium boydii (formerly Pseudallescheria
boydii) are now recognised as separate species and along with S. aurantiacum are
the principal human pathogens (Lackner et al. 2014a). The majority of infections
are mycetomas, the remainder include infections of the eye, ear, central nervous
system, internal organs and more commonly the lungs. Scedosporium dehoogii and
S. minutispora are mainly isolated from environmental samples and have been rarely
reported from clinical cases (Gilgado et al. 2005, Rainer and de Hoog 2006, Cortez et
al. 2008, Kaltseis et al. 2009).
Scedosporium prolificans has been transferred to the genus Lomentospora. L. prolificans
is phylogenetically and morphologically distinct from the remaining Scedosporium
species (Lennon et al. 1994, Lackner et al. 2014a).
Morphological identification of Scedosporium species has become increasingly
unreliable and molecular identification methods are now recommended. The conidial
states of S. apiospermum and S. boydii are morphologically indistinguishable; although
the latter is homothallic and produces ascocarps. S. aurantiacum also exhibits similar
conidial morphology but most strains produce a pale to bright yellow diffusible pigment
on potato dextrose agar.
Molecular Identification: Recommended genetic markers are ITS and β-tubulin
(Lackner et al. 2012a).
MALDI-TOF MS: A comprehensive ‘in-house’ database of reference spectra allows
accurate identification of Scedosporium and Lomentospora species (Lau et al. 2013,
Sitterlé et al. 2014).
References: McGinnis (1980), Domsch et al. (1980), McGinnis et al. (1982), Campbell
and Smith (1982), Rippon (1988), de Hoog et al. (2000, 2015), Gilgado et al. (2005),
Rainer and de Hoog (2006), Guarro et al. (2006), Lackner et al. (2014a).
Scedosporium apiospermum (Saccardo) Castellani and Chalmers
Synonymy: Pseudallescheria apiosperma Gilgado, Gené, Cano & Guarro
RG-2 organism.
Morphological Description: Colonies are fast growing, greyish-white, suede-like
to downy with a greyish-black reverse. Numerous single-celled, pale-brown, broadly
clavate to ovoid conidia, 4-9 x 6-10 µm, rounded above with truncate bases are
observed. Conidia are borne singly or in small groups on elongate, simple or branched
conidiophores or laterally on hyphae. Conidial development can be described as
annellidic, although the annellations (ring-like scars left at the apex of an annellide after
conidial secession) are extremely difficult to see. Erect synnemata may be present in
some isolates. Optimum temperature for growth is 30-37 O C.