CURVULARIA Mold SpeciesThe U.S. Government's Occupational Safety and Health Administration [OSHA] lists the following as the health effects of Curvularia: Allergen, Irritant, Hypersensitivity pneumonitis, Dermatitis. |
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Description and Habitats Curvularia is a dematiaceous filamentous fungus. Most species of Curvularia are facultative pathogens of soil, plants, and cereals in tropical or subtropical areas, while the remaining few are found in temperate zones. As well as being a contaminant, Curvularia may cause infections in both humans and animals.
Curvularia species
are commonly found as a parasites or saprobes (saprophytes) on graminaceous
hosts (= grasses and cereals). The conidia (= spores) are multicelled, pigmented
and often slightly curved. The end cells are often much paler than the
central cells. The conidia are borne in acropetal succession (= youngest at
the apex) through tiny pores in the conidiophore wall and are easily
dislodged. Based on the
mycological information provided by Mycology Online, the genus
Curvularia contains some 35 species which are mostly subtropical and
tropical plant parasites. However, three ubiquitous species have been
recovered from human infections, principally from cases of mycotic keratitis;
C. lunata, C. pallescens and C. geniculata. Curvularia is a dangerous mold can be a cause of human infection, including onychomycosis, keratitis, sinusitis, mycetoma, pneumonia, endocarditis, cerebral abscess, and disseminated infection. |
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Macroscopic Features Curvularia produces rapidly growing, woolly colonies on potato dextrose agar at 25°C. From the front, the color of the colony is white to pinkish gray initially and turns to olive brown or black as the colony matures. From the reverse, it is dark brown to black. Microscopic
Features Septate, brown hyphae, brown conidiophores, and conidia are visualized. Conidiophores are simple or branched and are bent at the points where the conidia originate. This bending pattern is called sympodial geniculate growth. The conidia (8-14 x 21-35 µm), which are also called the poroconidia, are straight or pyriform, brown, multiseptate, and have dark basal protuberant hila. The septa are transverse and divide each conidium into multiple cells. The central cell is typically darker and enlarged compared to the end cells in the conidium. The central septum may also appear darker than the others. The swelling of the central cell usually gives the conidium a curved appearance.
The number of the septa in the conidia,
the shape of the conidia (straight or curved), the color of the conidia
(dark vs pale brown), existence of dark median septum, and the prominence of
geniculate growth pattern are the major microscopic features that help in
differentiation of Curvularia spp. among each other. For instance,
the conidia of Curvularia lunata have 3 septa and 4 cells, while
those of Curvularia geniculata mostly have 4 septa and 5 cells. Laboratory Precautions
No special precautions other than
general laboratory precautions are required. Susceptibility Very few data are available and there is as yet no standard method for in vitro susceptibility testing of Curvularia spp. Notably, flucytosine yielded very high MICs for Curvularia isolates tested. The MICs of fluconazole were also quite high. In contrast, amphotericin B, ketoconazole, miconazole, itraconazole, and voriconazole showed favorable activity and generated acceptably low MICs for most of the Curvularia isolates tested. Caspofungin also appeared active in vitro against Curvularia lunata.
Treatment modalities for Curvularia
infections have not been standardized yet. Amphotericin B, itraconazole, and
terbinafine have so far been used to treat Curvularia infections.
However, the prognosis is usually poor, particularly for immunocompromised
patients. For treatment of allergic sinusitis, surgical treatment and
administration of steroids are usually required as well as antifungal
therapy. Surgery may be required in other infections as well, such as
keratitis and localized cutaneous infections. |
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