Pithomyces chartarum

The genus Pithomyces contains about 50 species commonly isolated from a wide range of plant material, also from air, soil, hay, sawn timber and ceiling plaster. 

Pithomyces chartarum has long been reported as causing facial eczema in sheep. However, recent molecular studies have identified at least two additional species P. sacchari and P. maydicus (de Cunha et al. 2014). Most human isolates are recovered from skin, nail, respiratory and sinus specimens.

RG-1 organism.

Conidiophore and conidia of Pithomyces chartarum.

Conidiophore and conidia of Pithomyces chartarum.

Morphological description: 
Colonies are fast growing, suede-like to downy and black. Conidiophores are pale olive, smooth or verrucose, 2.5-10 x 2-3.5 µm. Conidiogenous cells integrated, intercalary or terminal, indeterminate, with one to two loci of similar width in the conidiogenous cells. Conidia are muriform, medium to dark brown, echinulate to verrucose, three-(some up to five)-euseptate, slightly constricted at the septa, with one or both median cells divided by longitudinal septa, thick-walled, broadly ellipsoidal, apex obtuse, base truncate and characteristically with part of the conidiogenous cell remaining attached as a small pedicel, 18-29 x 10-17 µm.

Key features: 
Dematiaceous hyphomycete with multicelled conidia produced on small peg-like branches of the vegetative hyphae.

Molecular identification: 
ITS and D1/D2 sequencing recommended (de Cunha et al. 2014).

Ellis (1971, 1976), Domsch et al. (1980), Rippon (1988), de Hoog et al. (2000, 2015), de Cunha et al. (2014).

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