ABSTRACT
Chaetomium is a member of the ascomycete family Chaetomiaceae (Sordariales, Sordariomycetes). This species-rich genus encompasses approximately 130 accepted species; most of them colonize cellulose-rich substrates, such as plant debris, herbivore dung, paper, seeds, soil, textiles, or timber.1-3 Chaetomium spp. are generally referred to as soil saprophytes and are also commonly isolated from the soil by techniques for isolation of keratinophilic fungi.4,5 The genus includes predominantly homothallic species producing ostiolate perithecia that are usually covered with hairs and attached to substrates by rhizoidal hyphae. The morphology of ascomata, hairs, and ascospores (brownish, grayish, olive brown; never opaque) and maximum growth temperature are the most important features in species differentiation.2,3
Some anamorphs are associated with Chaetomium species and are produced simultaneously with ascomata or are phylogenetically embedded within a robust Chaetomium clade, but teleomorphs have not been observed. Botryotrichum, Humicola, Staphylotrichum, Trichocladium, Acremonium-like, Chrysosporium-like, Papulaspora-like, Paecilomyces-like, Scopulariopsis-like, and Histoplasma-like anamorphs have been reported.2,3,6-11 Many Chaetomium spp., including the majority of medically important species, lack anamorph and are known only by the sexual state. These species are exceptional in this aspect, because the infections due to fungi propagating strictly by ascospores are very rare in medical mycology.