CUTANEOUS MYCOSES

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CUTANEOUS MYCOSES
By
Dr. Emad AbdElhameed Morad
Lecturer of Medical Microbiology and Immunology
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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.

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Trichophyton
Affect

• Skin
• Hair
• Nails

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Microsporum
Affect

• Skin
• Hair

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Epidermophyton
Affect

• Skin
• Nails

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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.

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• 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.

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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).

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Tinea capitis(scalp)
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Tinea cruris(jock itch)
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Tinea corporis(the body)
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Tinea unguium (onychomycosis)Nails are
thickened, discolored and brittle
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Tinea pedis The lesion is called athletes foot
that occurs in those wearing shoes
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Tinea barbae(bearded area)
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• Favus is 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.
• Kerion is a severe lesion in the scalp which is
  caused by inflammation and hypersensitivity to
• zoophilic fungi.

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• 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.

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Laboratory diagnosis

• Woods 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.

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Specimen collection
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Dermatophytes in KOH mount of skin
scraping(Branching hyphae arthroconidia)
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Ectothrix and endothrix infection
Endothrix spores (T. tonsurans)
Ectothrix spores (Microsporum)
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(Favic hair)In favic hair, hyphae do not form
spores but can be found within the hair shaft
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• Culture
• Medium Sabourauds 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.

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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.
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Spiral hyphae
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Trichophyton rubrum
Conidia are microconidia which are small and
piriform in shape.
The fungus has white cottony observe surface
deep red non diffusible pigment on the reverse
surface
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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
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Microsporum gypseum
Conidia are macroconidia which are thin
echinulate walled, 4 6 cells
Colonies of the fungus are tan powdery.
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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.
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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.

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GOOD LUCK