2. Superficial

7/29/2019 2. Superficial

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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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2. Superficial