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CUTANEOUS MYCOSES. By. Dr. Emad AbdElhameed Morad. Lecturer of Medical Microbiology and Immunology. Dermatophytes. More than 100 species have been described for dermatophytes, only about 40 are considered and less than half of these are associated with human disease.

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cutaneous mycoses

CUTANEOUS MYCOSES

By

Dr. Emad AbdElhameed Morad

Lecturer of Medical Microbiology and Immunology

dermatophytes
Dermatophytes
  • More than 100 species have been described for dermatophytes, only about 40 are considered and less than half of these are associated with human disease.
  • Dermatophytes include three genera which are: trichophyton, microsporum and epidermophyton.
  • According to sporulation:
  • Asexual (anamorphic state):chains of arthroconidia.
  • Sexual (teleomorphic state):trichophyton and microsporum are ascomycetes but that of epidermophyton is not observed.

Dr. Emad AbdElhameed Morad

trichophyton
Trichophyton

Affect

  • Skin
  • Hair
  • Nails

Dr. Emad AbdElhameed Morad

microsporum
Microsporum

Affect

  • Skin
  • Hair

Dr. Emad AbdElhameed Morad

epidermophyton
Epidermophyton

Affect

  • Skin
  • Nails

Dr. Emad AbdElhameed Morad

pathogenesis
Pathogenesis
  • Dermatophytes affect keratinized tissues (skin, hair and nails) as they produce keratinase enzyme which digests the keratin.
  • The intact skin is an important barrier against infection.
  • Heat and humidity enhance the infection.
  • Infection may be:
  • Anthropophilic: from man to man by direct contact.
  • Zoophilic: from the animals.
  • Geophilic: from the soil.

Dr. Emad AbdElhameed Morad

slide8
Anthropophilic group tends to cause chronic infections which are difficult to cure.
  • Zoophilic and geophilic groups tend to cause acute inflammatory lesions that respond well to therapy.

Dr. Emad AbdElhameed Morad

clinical picture
Clinical picture
  • The lesion is called ring worm or tinea.
  • Tinea comes from the latin word moth.
  • The lesion is called ring worm because it is ring shaped with red raised border of active inflammation and a healing center.
  • The clinical forms of the disease are:
  • Tinea capitis (head) & tinea cruris (groin area) & tinea corporis (body) & tinea unguium (nails) & tinea pedis (feet) & tinea barbae (beard) & tinea manus (hands).

Dr. Emad AbdElhameed Morad

tinea capitis scalp
Tinea capitis(scalp)

Dr. Emad AbdElhameed Morad

tinea cruris jock itch
Tinea cruris(jock itch)

Dr. Emad AbdElhameed Morad

tinea corporis the body
Tinea corporis(the body)

Dr. Emad AbdElhameed Morad

tinea pedis the lesion is called athlete s foot that occurs in those wearing shoes
Tinea pedis The lesion is called athlete’s foot that occurs in those wearing shoes

Dr. Emad AbdElhameed Morad

tinea barbae bearded area
Tinea barbae(bearded area)

Dr. Emad AbdElhameed Morad

slide17
Favusis a form of tinea capitis which is caused by Trichophyton schoenleinii. Favus comes from the

latin word honey comb. In favus

waxy crusts called scutula

surround the hair follicles.

  • Kerionis a severe lesion in the scalp which is caused by inflammation and hypersensitivity to

zoophilic fungi.

Dr. Emad AbdElhameed Morad

slide18
Dermatophytid reaction:in the course of dermatophytosis, the individual may become hypersensitive to fungal elements and develop allergic manifestations called dermatophytids usually vesicles elsewhere in the body most often on the hand. Trichophytin skin test is markedly positive.

Dr. Emad AbdElhameed Morad

laboratory diagnosis
Laboratory diagnosis
  • Wood’s light (UV light at wave length 365 nm):
    • Microsporum lesions will fluoresce brilliant green.
  • Specimen:
    • Skin scales, nails, hair.
  • Microscopic examination of these specimens using KOH 10%:
    • KOH dissolves keratin but does not affect fungi. Branching septate hyphae are detected among epithelial cells.
    • Spores (arthroconidia) may be detected outside the hair shaft (ectothrix) or inside the hair shaft (endothrix). An exception is favus in which hyphal elements are seen in the hair shafts.

Dr. Emad AbdElhameed Morad

specimen collection
Specimen collection

Dr. Emad AbdElhameed Morad

dermatophytes in koh mount of skin scraping branching hyphae arthroconidia
Dermatophytes in KOH mount of skin scraping(Branching hyphae + arthroconidia)

Dr. Emad AbdElhameed Morad

ectothrix and endothrix infection
Ectothrix and endothrix infection

Endothrix spores

(T. tonsurans)

Ectothrix spores

(Microsporum)

Dr. Emad AbdElhameed Morad

favic hair in favic hair hyphae do not form spores but can be found within the hair shaft
(Favic hair)In favic hair, hyphae do not form spores but can be found within the hair shaft

Dr. Emad AbdElhameed Morad

slide24

Culture:

  • Medium: Sabouraud’s dextrose agar to which we add chloramphenicol and cycloheximide.
  • Incubation: at the room temperature.
  • Duration: Up to 4 weeks.
  • Identification is done by:
  • Morphology and color on the observe and reverse surfaces.
  • Slide culture to study the morphology and color of conidia using lactophenol cotton blue.

Dr. Emad AbdElhameed Morad

trichophyton mentagrophytes
Trichophyton mentagrophytes

Conidia:are macroconidia which are smooth, thin walled and cylindrical and microconidia which are grape like clusters on terminal branches.

Colonies may be cottony to granular.

Dr. Emad AbdElhameed Morad

slide26

Spiral hyphae

Dr. Emad AbdElhameed Morad

trichophyton rubrum
Trichophyton rubrum

Conidia:are microconidia which are small and piriformin shape.

The fungus has white cottony observe surface + deep red non diffusible pigment on the reverse surface

Dr. Emad AbdElhameed Morad

microsporum canis
Microsporum canis

Conidia:are macroconidia which are thick echinulate walled, 8-15 cells + curved tip

The fungus has white cottony observe surface + deep yellow on the reverse surface

Dr. Emad AbdElhameed Morad

microsporum gypseum
Microsporum gypseum

Conidia:are macroconidia which are thin echinulate walled, 4 – 6 cells

Colonies of the fungus are tan powdery.

Dr. Emad AbdElhameed Morad

epidermophyton floccosum
Epidermophyton floccosum

Conidia: are macroconidia which are smooth walled, clavate, 2 – 4 cells, groups of two or three

Colonies of the fungus are flat, velvety with olive green tinge.

Dr. Emad AbdElhameed Morad

treatment
Treatment
  • For skin infections: topical azoles (miconazole, clotrimazole). They act by inhibiting ergosterol synthesis.
  • For hair infections: griseofulvin. It acts by inhibiting the microtubule function in the fungus.

Dr. Emad AbdElhameed Morad