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