DESCRIPTIONS OF MEDICAL FUNGI

Descriptions of Medical Fungi 223
Trichothecium roseum has a worldwide distribution and is often isolated from decaying
plant substrates, soil, seeds of corn, and food-stuffs (especially flour products). It is
occasionally isolated as a saprophyte in the clinical laboratory.
RG-1 organism.
Trichothecium roseum (Persoon) Link
Morphological Description: Colonies are moderately fast growing, flat, suede-like to
powdery, initially white but becoming rosy, pink or orange with age. The conidiophores
are indistinguishable from the vegetative hyphae until the first conidium is produced.
They are erect, unbranched, often septate near the base, more or less roughwalled,
bearing basipetal zig-zag (alternating) chains of conidia at the apex. Note:
The conidiophore is progressively shortened with the formation of each conidium i.e.
retrogressive conidial development. Conidia are two-celled ellipsoidal to pyriform, with
an obliquely truncate basal scar, hyaline, smooth to delicately roughened and thickwalled.
Comment: T. roseum should not be confused with Nannizzia nanum. Colonies of the
latter may be pinkish-buff in colour and also produce ovoid to pear-shaped, mostly twocelled
macroconidia with thin, verrucose walls. However, N. nanum usually produces
a red-brown reverse pigment and the two-celled macroconidia are sessile and formed
singly, they are not produced in basipetal chains as in T. roseum.
Molecular Identification: Summerbell et al. (2011) revised the genus using D1/D2
sequences for phylogenetic analysis and sequence based identification.
Key Features: Hyphomycete, basipetal zig-zag chains of two-celled conidia showing
retrogressive development where the conidiophore becomes progressively shorter.
References: McGinnis (1980), Domsch et al. (2007), Rippon (1988), Samson et al.
(1995), Summerbell et al. (2011).
20 µm
Trichothecium roseum conidiophores showing retrogressive conidial development.