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Culture of Cladosporium cladosporioides
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Conidiophores
and conidia of
Cladosporium
cladosporioides
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Colonies are rather slow growing, mostly olivaceous-brown to
blackish brown but also sometimes grey, buff or brown,
suede-like to floccose, often becoming powdery due to the
production of abundant conidia. Vegetative hyphae, conidiophores
and conidia are equally pigmented. Conidiophores are more or
less distinct from the vegetative hyphae, are erect, straight or
flexuous, unbranched or branched only in the apical region, with
geniculate sympodial elongation in some species. Conidia are 1-
to 4-celled, smooth, verrucose or echinulate, with a distinct
dark hilum and are produced in branched acropetal chains. The
term blastocatenate is often used to describe chains of conidia
where the youngest conidium is at the apical or distal end of
the chain. Note, the conidia closest to the conidiophore and
where the chains branch, are usually "shield-shaped".
The presence of shield-shaped conidia, a distinct hilum, and
chains of conidia that readily disarticulate, are diagnostic for
the genus Cladosporium.
For identification,
isolates are best grown on potato dextrose agar or 2% malt
extract agar at 20-25C. Microscopic mounts are best made using a
cellotape flag or slide culture preparation mounted in
lactophenol cotton blue. A drop of alcohol is usually needed to
detach the cellotape flag from the stick, and to act as a
wetting agent.
For
more cladosporium mold pictures, please visit or click on:
Cladosporium Mold Picture
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Description
and Natural Habitats
Cladosporium
is a dematiaceous (pigmented) mold widely distributed in air and rotten
organic material and frequently isolated as a contaminant on foods. Some
species are predominant in tropical and subtropical regions. Also, some Cladosporium
spp. were isolated from fish and were associated with findings of
infection.
Species
The genus Cladosporium
includes over 30 species. The most common ones include Cladosporium
elatum, Cladosporium herbarum, Cladosporium sphaerospermum,
and Cladosporium cladosporioides.
Pathogenicity
and Clinical Significance
Cladosporium
species are causative agents of skin lesions, keratitis, onychomycosis,
sinusitis and pulmonary infections.
Macroscopic
Features
The growth
rate of Cladosporium colonies is moderate on potato dextrose agar
at 25°C and the texture is velvety to powdery. Similar to the other
dematiaceous fungi, the color is olivaceous green to black from the
front and black from the reverse. Most of the Cladosporium spp.
do not grow at temperatures above 35°C.
Microscopic
Features
Cladosporium
species produce septate brown hyphae, erect and pigmented conidiophores,
and conidia. While the conidiophores of Cladosporium cladosporioides
and Cladosporium sphaerospermum are not geniculate, those of Cladosporium
herbarum have a geniculate appearance. In addition, conidiophores of
Cladosporium herbarum bear terminal and intercalary swellings.
Conidia of Cladosporium spp. in general are elliptical to
cylindrical in shape, pale to dark brown in color and have dark hila.
They occur in branching chains that readily disarticulate. Conidial wall
is smooth or occasionally echinulate. Cladosporium cladosporioides
produces unicellular conidia. On the other hand, those of Cladosporium
herbarum are two-to four-celled. Cladosporium sphaerospermum
produces elongate and septate shield cells which are also known as
ramoconidia.
Laboratory
Precautions
Cladosporium
species should be handled with care in a biological safety cabinet.
Susceptibility
Very limited
data are available on susceptibility profiles of Cladosporium species.
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