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SUPERFICIAL MYCOSES. By. Dr. Emad AbdElhameed Morad. Lecturer of Medical Microbiology and Immunology. Superficial mycoses. 1- Pityriasis versicolor Skin 2- Tinea nigra Skin 3- Black piedra Hair 4- White piedra Hair. Pityriasis versicolor.
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SUPERFICIAL MYCOSES By Dr. Emad AbdElhameed Morad Lecturer of Medical Microbiology and Immunology
Superficial mycoses 1- Pityriasis versicolor Skin 2- Tinea nigra Skin 3- Black piedra Hair 4- White piedra Hair
Pityriasis versicolor • Causative agent: • Malassezia furfuris the causative agent. • Malasseszia furfur is a lipophilic fungus living on the skin as part of the normal flora. • So, it is cultivated on media containing fatty substances like olive oil.
Diseases caused by Malassezia furfur: • Pityriasis versicolor is associated with hyperpigmented or hypopigmented macules usually on the chest and upper back of the patients. • Pityriasis folliculitis. • Catheter acquired fungemiain patients receiving total parenteral nutrition containing lipid emulsion. Pityriasis versicolor
Laboratory diagnosis: • Wood’s lamp: • Wood’s light is ultraviolet light at wave length 365 nm. • The lamp is held four or five inches from the affected skin. If pityriasis versicolor is present on the skin, the affected skin will appear yellowish green in color. • Specimen: • Skin scrapings from the lesions. • Direct Microscopy: • The skin scrapings are mounted in 10-20% KOH. • It will show spherical budding cells and short unbranchedangular septatehyphae (spaghetti and meat balls). • These microscopic features are diagnostic for Malassezia furfur and culture is not necessary.
Treatment: • Daily application of selenium sulfide. • Topical or oral azoles are very effective.
Tinea nigra • Causative agent: • Exophiala (Hortae) werneckiiis the causative agent. • It is a saprophytic fungus which occurs in the soil. • It is a dematicaeous fungus (contains melanin in its cell wall and appear dark in color under the microscope).
Clinical picture: • Brown to black discoloration of the palm of the hand. • So, Tinea nigra is also called Tinea palmaris. • But, it may affect the sole of the foot. Tinea nigra
Laboratory diagnosis: • Specimen: • Skin scrapings from the lesions. • Direct Microscopy: • The skin scrapings are mounted in 10-20% KOH. • It will show brown to black two celled yeast cells + branched septate hyphae.
Treatment: • Keratolytic solutions like salicylic acid. • Azoles are also effective.
Black piedra • Piedraia hortaiis the causative agent. • It is a dematicaeous mold. • It affects the hair like beard, moustache and scalp & pubic hair. • It causes brown to black hard nodules around the hair shaft. • It is treated by removal of infected hairs + topical antifungal drugs.
White piedra • Trichosporon beigelii is the causative agent. • It is a mold. • It affects the hair. • It causes large, white to yellow soft nodules around the hair shafts. • It is treated similar to black piedra.