DESCRIPTIONS OF MEDICAL FUNGI
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Descriptions of Medical Fungi 57<br />
Cladosporium species are ubiquitous worldwide, and commonly isolated from soil and<br />
organic matter. They represent the most frequently isolated airborne fungi. The genus<br />
has undergone a number of revisions. The well-known thermotolerant ‘true humanpathogenic<br />
species, formerly known as C. bantiana, C. carrionii and C. devriesii,<br />
characterised by the absence of conidiophores, and unpigmented conidial scars, were<br />
reclassified in Cladophialophora (de Hoog et al. 1995, Bensch et al. 2012). The remaining<br />
species of medical interest were C. cladosporioides, C. herbarum, C. oxysporum,<br />
and C. sphaerospermum. More recently, extensive revisions based on polyphasic<br />
approaches have recognised 169 species, and demonstrated that C. cladosporioides,<br />
C. herbarum and C. sphaerospermum are species complexes encompassing several<br />
sibling species that can only be distinguished by phylogenetic analyses (Crous et al.<br />
2007, Schubert et al. 2007, Zalar et al. 2007, Bensch et al. 2010, 2012).<br />
Sandoval-Denis et al. (2015) analysed 92 clinical isolates from the United States<br />
using phenotypic and molecular methods, which included sequence analysis of the<br />
ITS and D1/D2 regions, partial EF-1α and actin genes. Surprisingly, the most frequent<br />
species was Cladosporium halotolerans (15%), followed by C. tenuissimum (10%), C.<br />
subuliforme (6%), and C. pseudocladosporioides (5%). However, 40% of the isolates<br />
did not correspond to any known species and were deemed to represent at least 17<br />
new lineages for Cladosporium. The most frequent anatomic site of isolation was the<br />
respiratory tract (55%), followed by superficial (28%) and deep tissues and fluids (15%).<br />
Species of the two recently described Cladosporium-like genera Toxicocladosporium<br />
and Penidiella were also reported for the first time from clinical samples (Sandoval-<br />
Denis et al. 2015).<br />
RG-1 organisms.<br />
Cladosporium Link ex Fries<br />
Morphological Description: Colonies are slow growing, mostly olivaceous-brown<br />
to blackish-brown but also sometimes grey, buff or brown, suede-like to floccose,<br />
often becoming powdery due to the production of abundant conidia. The reverse is<br />
olivaceous-black. Vegetative hyphae, conidiophores and conidia are equally pigmented.<br />
Conidiophores are more or less distinct from the vegetative hyphae, being erect,<br />
straight or flexuose, unbranched or branched only in the apical region, with geniculate<br />
sympodial elongation in some species. Conidia are produced in branched acropetal<br />
chains, being smooth, verrucose or echinulate, one to four-celled, and have a distinct<br />
dark hilum. The term blastocatenate is often used to describe chains of conidia where<br />
the youngest conidium is at the apical or distal end of the chain. Note: The conidia<br />
closest to the conidiophore, and where the chains branch, are usually “shield-shaped”.<br />
The presence of shield-shaped conidia, a distinct hilum, and chains of conidia that<br />
readily disarticulate, are characteristic of the genus Cladosporium.<br />
Key Features: Dematiaceous hyphomycete forming branched acropetal chains of<br />
conidia, each with a distinct hilum.<br />
Molecular Identification: Genus level identification is usually sufficient and<br />
morphological identification can be confirmed by ITS and D1/D2 sequence analysis.<br />
Multilocus gene analysis of the ITS, D1/D2, EF-1α and actin gene loci is necessary for<br />
accurate species identification (Bensche et al. 2012).