DESCRIPTIONS OF MEDICAL FUNGI

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Descriptions of Medical Fungi
Trichosporon Behrend
Trichosporon species are urease-positive, non-encapsulated basidiomycetous yeasts
characterised by the development of hyaline, septate hyphae that fragment into oval or
rectangular arthroconidia. Some blastoconidia are also seen. The colonies are usually
raised and have a waxy appearance, which develop radial furrows and irregular folds.
They are widely distributed in the environment and many have different habitats, usually
occupying narrow ecological niches. Some are soil borne and others are associated
with humans and animals (Colombo et al. 2011, Sugita 2011, Arendrup et al. 2014).
The genus has undergone major taxonomic revision (Gueho et al. 1992, de Hoog et
al. 2000, Rodriguez-Tudela et al. 2005). In particular, the name Trichosporon beigelii is
now obsolete, and previously described infections reported in the literature under this
name could in fact be due to any one of the species listed below.
Six species are of clinical significance: T. asahii, T. asteroides, T. cutaneum, T.
inkin, T. mucoides and T. ovoides. Other species reported from human and animal
infections include T. dermatis, T. domesticum, T. faecale, T. jirovecii, T. loubieri and T.
mycotoxinovorans (Rodriguez-Tudela et al. 2005, Chagas-Neto et al. 2008, Colombo
et al. 2011).
Trichosporon species are a minor component of normal skin flora, and are widely
distributed in nature. They are regularly associated with the soft nodules of white piedra,
and have been involved in a variety of opportunistic infections in the immunosuppressed
patient. Disseminated infections are most frequently (75%) caused by T. asahii
(Arendrup et al. 2014) and have been associated with leukaemia, organ transplantation,
multiple myeloma, aplastic anaemia, lymphoma, solid tumours and AIDS. Disseminated
infections are often fulminate and widespread, with lesions occurring in the liver, spleen,
lungs and gastrointestinal tract. Infections in non-immunosuppressed patients include
endophthalmitis after surgical extraction of cataracts, endocarditis usually following
insertion of prosthetic cardiac valves, peritonitis in patients on continuous ambulatory
peritoneal dialysis (CAPD), and intravenous drug abuse.
Note: Genus identification is mandatory for clinical management and should be
performed and provided in a timely manner. Species identification remains difficult and
requires molecular analysis or MALDI-TOF MS (with an extensive database) (Arendrup
et al. 2014).
Molecular Identification: ITS and D1/D2 sequencing is required for accurate species
identification (Arendrup et al. 2014).
MALDI-TOF MS: A promising identification tool to accurately identify species (with an
extensive database) (Kolecka et al. 2013).
Comment: The API 20C yeast identification system is recommended for sugar
assimilation tests.
References: Kurtzman and Fell (1988), Gueho et al. (1992), de Hoog et al. (2000,
2015), Rodriguez-Tudela et al. (2005), Chagas-Neto et al. (2008), Guo et al. (2011),
Xiao et al. (2013).