(described by de Not in 1849)
Taxonomic classification
Kingdom: Fungi
Phylum: Ascomycota
Class: Euascomycetes
Order: Dothideales
Family: Lophiostomataceae
Genus: Pyrenochaeta
Description and Natural Habitats
Pyrenochaeta is a dematiaceous filamentous fungus that inhabits the soil and plant debris, particularly in tropical climates. Pyrenochaeta species are pathogens for various plant species and among the rare causes of some specific human infections.
Species
The genus Pyrenochaeta contains three active species; Pyrenochaeta mackinnonii, Pyrenochaeta unguis-hominis, and Pyrenochaeta romeroi. The color and texture of the colony help in differentiation of the species from eachother [531]. While many isolates previously identified as Madurella grisea have been reidentified as Pyrenochaeta romeroi, some authorities believe that Pyrenochaeta romeroi should be classified in the genus Phoma.
See the list of obsolete names, synonyms, and telemorphs for Pyrenochaeta spp.
Pyrenochaeta romeroi has been isolated from cases with mycetoma. The grains are soft, irregular, and black with a subhyaline center. Pyrenochaeta unguis-hominis, on the other hand, has been isolated from the infected nails of some cases [673]. However, its role in development of onychomycosis remains questionable.
Macroscopic Features
Colonies of Pyrenochaeta grow moderately rapidly. They are flat and woolly to cottony. From the front, the color is white initially and becomes olivaceous green to olivaceous gray. Reverse is dark [531, 2202].
Microscopic Features
Septate, hyaline to subhyaline hyphae, pycnidia, and conidia are observed. Pycnidia (sing. pycnidium; round or flask-shaped fruiting body containing conidia) are globose to flask-shaped and ostiolate. They are brown to black and have setae (rigid hair located on the pycnidia) arising from their upper portion. Phialides arise from the inner lining of the pycnidia. Conidia (2-4 x 1-2 µm) are one-celled, oval to cylindrical, hyaline, and straight or slightly curved [531, 2202].
Compare to
Coniothyrium
Phoma
Phomopsis
Pleurophoma
Pyrenochaeta differs from Phoma by having setae.
Laboratory Precautions
No special precautions other than general laboratory precautions are required.
Susceptibility
Very limited data are available. Ketoconazole, itraconazole [2313], and terbinafine [2308, 2309] appear active in vitro against Pyrenochaeta romeroi.
Ketoconazole has so far been used in treatment of cases with mycetoma due to Pyrenochaeta romeroi [2312].