Piedraia hortae
| Piedraia hortae | |
|---|---|
| Scientific classification | |
| Kingdom: | Fungi |
| Phylum: | Ascomycota |
| Class: | Dothideomycetes |
| Order: | Capnodiales |
| Family: | Piedraiaceae |
| Genus: | Piedraia |
| Species: | Piedraia hortae |
| Binomial name | |
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P. hortae (Brumpt) Fonseca & Leão (1928) |
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| Synonyms | |
Piedraia hortae is a superficial fungus that exists in the soils of tropical and subtropical environments and affects both sexes of all ages. The fungus grows very slowly, forming dark hyphae, which contain chlamydoconidia cells and black colonies when grown on agar. Piedraia hortae is a dermatophyte and causes a superficial fungal infection known as black piedra, which causes the formation of black nodules on the hair shaft and leads to progressive weakening of the hair. The infection usually infects hairs on the scalp and beard, but other varieties tend to grow on pubic hairs. The infection is usually treated with cutting or shaving of the hair and followed by the application of anti-fungal and topical agents. The fungus is used for cosmetic purposes to darken hair in some societies as a symbol of attractiveness.
When grown on agar at 25 °C (77 °F) Piedraia hortae grows very slowly to form black-greenish, limited and pointed colonies.Piedraia hortae taken from infected hairs have dark brown nodules, which are made up of ascostroma. The nodules have a gritty feel, organized in a stromatic fashion and have a high concentration of chitin and melanoid pigments. The colonies produce a red pigment and remain smooth and covered with short aerial hyphae. Microscopically, P. hortae produces short, dark hyphae containing thick-walled resting cells. The ascomata consist of irregularly shaped pseudothecia that are black in colour. Each ascoma contains a single ascus containing eight ascospores. The ascospores are dark, curved and become very narrow at the ends forming whip-like appendages. Affected hairs develop stone-like black nodules affixed to the hair shaft that cause weakness of the hair. Infected hairs treated with potassium hydroxide fluoresce under ultraviolet light despite that the fungus itself does not normally fluoresce. Fluorescence of the piedra indicates secondary contamination by bacteria. Identification is easily achieved by microscopic examination of the hair nodules, and can be confirmed by sequence analysis of the nuclear ribosomal internal transcribed spacer region.
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