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Dermatophytes infections

اللطيفعبد ناهض .أ

الشفاء.م-الميكربيولوجىرئيس قسم

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Abstract• Diagnosis of dermatophytes infections

using two methods:

• 1-Direct microscopic examination (KOH

method)

• 2-Fungal culture on sabouraud dextrose

agar with antibiotics).

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Introduction• Dermatophytes are fungal organisms that are able

to exist within the keratinous elements of living

skin and which belong to one of 3 genera,

Epidermophyton Microsporum,and

Trichophyton.

• Dermatophytes require keratin for growth and

therefore infect hair, nails, and superficial skin,

with clinical manifestations named for the area

affected.

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• Dermatophytoses occur in all populations

worldwide, but are generally more common among

immunocompromised patients.

• Tinea infections have alternately been called

“ringworm,” because of the lesions that present as a

circular or oval clearing surrounded by a red, scaly,

elevated border (“ring”).

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• Besides the dermatophytoses,

superficial infections may also result

from infection with other fungi,

including the Malassezia species of

yeast, and candida.

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Anatomy of the Skin

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Epidermis

• Outermost layer of the skin

• Its layers are made of Mostly dead cells.

• Most of the cells of the epidermis undergo rapid

cell division (mitosis).

• As new cells are produced, they push older cells

to the surface of the skin. The older cells

become flattened, lose their cellular contents and

begin making keratin.

• Keratin:- a tough fibrous protein that forms the

basic structure of hair, nails, and skin.

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Layers of Epidermis

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Hair Follicles

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Nails

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ETIOLOGIC AGENTS• Three fungal genera cause tinea infections:

Microsporum, Trichophyton, and more rarely,

Epidermophyton .

• Species may be grouped by their source of

human infection

• 1-Anthropophilic:from human, the most

frequent causes of onychomycosis and other

superficial dermatophytoses

• 2- Zoophilic:from animals, especially dogs, cat.

• 3- Geophilic: from soil, less commonly,

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Zoophilic dermatophytoses

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Zoophilic dermatophytoses

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Zoophilic dermatophytoses

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• The major causative species differ geographically and may change in prevalence over time owing to population movements from immigration or travel.

• M. canis is a zoophilic organism frequently picked up by humans from contact with animals such as dogs and cats.

• The Malassezia yeast species are associated with the superficial fungal infections pityriasis (tinea) versicolor (PV) and seborrheic dermatitis (SD).

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PATHOGENESIS AND

IMMUNOLOGY

• The dermatophytes colonize keratinized tissue

of the stratum corneum; invasion by

anthropophilic species usually result in less

inflammation than that of zoophilic or geophilic

species.

• The epidermis functions as a barrier to

microorganisms, and commensal flora may also

help reduce infection by pathogens .

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• Entry into the stratum corneum may result from

trauma to the skin or some other breach of the

skin barrier.

• Excessive sweating and occlusive clothing

/footwear aid in providing a warm, moist

environment conducive to tinea infection.

Infection may be transferred from one area of

the body to another. Infection may also be

transmitted between individuals by direct or

indirect contact with scales containing fungal

arthroconidia from infected individuals

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CLINICAL MANIFESTATIONS• 1-Tinea Pedis :

• Tinea pedis is dermatophytoses of the feet, and may

involve the interdigital spaces.

• Tinea pedis is also called athlete’s foot and ringworm

of the feet.

• There are three common presentations recognized in

tinea pedis: interdigital, moccasin, and vesicobullous

• This infection is most commonly produced by T.

rubrum and T.mentagrophytes.

• Secondary bacterial or yeast infection is also possible.

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Tinea Manuum• Tinea manuum is a rare form that primarily

affects the palmar areas of the hands, and

presents as chronic, dry, scaly, hyperkeratotic

skin with minimal erythema .

• Infections are most frequently caused by T.

rubrum. Tinea manuum may accompany tinea

pedis or onychomycosis, and a two feet–one

hand syndrome has been noted to occur .

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Tinea Corporis• Tinea corporis is a superficial dermatophyte infection

of the glabrous skin, excluding the scalp, beard, face,

hands, feet, and groin.

• Infection of the skin of the trunk, legs and arms with

a dermatophyte.

• Infection frequently contracted from a household

pet.

• May follow infection of another body site.

• Person to person transmission may occur in contact

sports.

• M. canis from cats and dogs most frequent.

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Tinea Corporis

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Tinea Cruris:-

• tinea cruris is a dermatophyte infection of the

genitalia,pubic area, perineal skin, and perianal skin .

• The scrotum and labia majora are typically not

affected. Infection is more common in men than in

women.

• Often transferred from another infected body site.

• Highly contagious via contaminated towels, floors,

etc.

• Anthropophilic dermatophytes Epidermophyton

floccosum and Trichophyton rubrum are most

common.

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Tinea Capitis• Infection of the scalp involves hyphal

proliferation in the stratum corneum that

extends into the hair follicle orifice and hair

shaft.

• Inflammatory tinea capitis is associated with

zoophilic,Anthropophilic or geophilic species .

• Mild scaling lesions to widespread alopecia.

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• Kerion: highly inflammatory, suppurating lesion

caused by black dot appearance seen with ectothrix

hair invasion.

• Favus is a distinctive infection with grey, crusting

lesions.

• Asymptomatic carrier state recognized, may promote

spread of infection.

• Affected hair may appear grey due to coating with

arthroconidia.

• infection is associated with Microsporum and

Trichophyton species.

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Ectothrix

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Onychomycosis

• The term onychomycosis is used to describe infection of the nails with fungi. In addition to the dermatophytes and Candida spp. there are a group of filamentous moulds that can invade nail tissue.

• No specific clinical features; the nail becomes lustreless and thickened. Small pits and streaks may appear in the nail plate, which is at first white, then yellow, brown, green or black

• Multiple nails may be affected, and varying degrees of nail plate area may be covered .

• infections are usually caused by T. soudanense or T. violaceum, other yeast and non dermatophyte molds.

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Tinea Unguium• Tinea unguium, a dermatophyte infection of the nail.

• 19 Risk factors for this infection include aging,

diabetes, poorly fitting shoes, and the presence of

tinea pedis.

• Toenails more often infected than fingernails.

• Infection often follows infection of another body site.

• Most commonly caused by anthropophilic species

Trichophyton mentagrophytes and T. rubrum.

• Affects up to 8% of adult population.

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Tinea Unguium

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Tinea Barbae• Tinea barbae involves the skin and coarse

hairs of the beard and mustache area. This

dermatophyte infection occurs in adult men

and hirsute women.

• The usual cause is a zoophilic organism, farm

workers are most often affected.

• Tinea barbae may cause scaling, follicular

pustules, and erythema.

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Tinea Barbae

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Tinea Faciei• Tinea faciei tends to occur in the non

bearded area of the face. The patient

may complain of itching and burning,

which become worse after sunlight

exposure.

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Tinea Faciei

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NON-DERMATOPHYTE MOLDS

• Several molds demonstrate an ability to invade

keratinous tissue and cause conditions

resembling dermatophytosis.

• The infection caused by these organisms are

clinically indistinguishable from those due to

dermatophytes .

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Pityriasis Versicolor• Pityriasis versicolor presents as well-defined lesions,

with a fine scale from desquamation, that are either hyper pigmented or hypo pigmented .

• There is a large variation in lesion size from macules to entire trunk coverage .

• Lesions are predominant in areas with a high number of sebaceous glands such as the scalp, chest, and back, as well as upper arms and face

• Facial lesions are more common in children than adults .

• Due to Malassezia yeasts (M. furfur M. globosa, and other species.

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Pityriasis Versicolor

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Materials and methods

1-Materials:

• Sterilized scalpels, forceps, Petri dishes.

• Slides ,cover slides & sterile blade.

• Modified Sabouraud dextrose agar with antibiotics

• Instruments :

• incubator at 25-30C, autoclave, light microscope, balance 4 digit, glassware, and other conventional microbiological equipments and chemicals :20% KOH .

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Materials

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Clinical Material

• Skin Scrapings, nail scrapings, scalp and

hairs. For a laboratory diagnosis, clinicians

should be aware of the need to generate

an adequate amount of suitable clinical

material. The laboratory needs enough

specimen to perform both microscopy

and culture.

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Collection procedure• 1-Cleanse the affected area with 70%v/v ethanol.

• 2-Collect skin scales, crusts, pieces of nail, or hairs on

clean slide as follows:

• *Skin scales: Collect by scraping the surface of the

margin of the lesion using sterile scalpel blade.

• *Nail pieces: Collect by taking snipping of the infected

part of the nail using sterile scissors.

• *Hairs: Collect by removing dull broken hairs from

the margin of the lesion using sterile tweezers.

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Collection procedure

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Direct microscope• Used to visualizing fungal elements and confirming

the diagnosis of dermatophyte.

• Fungi are usually larger than bacteria, and in material from skin ,hair, or nail ,they can be seen by direct microscopy provided the material is first softened and cleared with strong alkali such as 200g/I(20%w/v)potassium hydroxide(KOH).

• The purpose of the alkali is to digest the keratinsurrounding the fungi so that the hyphae and spores can be seen.

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Slide preparation with KOH• 1.Place a drop of potassium hydroxide solution on

a slide.

• 2.Transfer the specimen (small pieces)to the drop

of KOH, and cover with cover glass.

• Note: To assist clearing ,hairs should not be more

than 5mm long, and skin scales, crusts and nail

snips should not be more than 2mm across.

• Hairs clear within 5-10minutes.Skin scales and

crusts usually take 20-30minutes. Pieces of nail,

however, may take several hours to clear.

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Hyphae

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Hyphae

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Hyphae

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Hyphae

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Malassezia furfur

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Malassezia furfur

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Arthrospores

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Spores

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Spores: hair

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Spores :nail

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Culture

• Useful to confirm the diagnosis of dermatophyte when long-

term oral therapy is being considered, and to identify

dermatophyte species .

• Specimen are cultured as follows:

• Skin scales,crusts,pieces of nail:

• 1.Using a sterile blade or scissors, cut the specimens into

pieces as small as possible.

• 2.Using sterile ,inoculate the small pieces (a few millimeters

apart) ,on the surface of a plate of sabouraud dextrose agar.

• 3.Incubate at incubator (25-30 C). for up to 3 weeks,

examining every few days for growth.

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Hairs• 1.Using a sterile scissors ,cut the hairs (portion

nearest to the hair root) into small pieces about3-

5 mm long.

• 2.Using sterile tweezers, inoculate the pieces of

hair on the surface of a plate of sabouraud

dextrose agar.

• 3.Incubate at incubator(25-30 C) for up o 3

weeks, examining every few days for growth.

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Examination of ringworm cultures:

• The colonial appearance (macroscopically) of

the different species of dermatophyte may be

helpful in diagnosis of dermatophytes.

• The identification of the various species is made

by examining microscopically a portion of the

colony for spores and characteristic hyphae as

follows:

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• 1.Using a sterile needle with 5 mm of its end

bent at a 45 angel, remove carefully a portion of

the colony and transfer it to a drop of saline on

a slide, and cover with a cover glass.

• 2.Examine the preparation using the10X and

40X objectives with the condenser

• Iris diaphragm adjusted to give maximum

contrast.

• 3.Look for the presence of macroconidia,

,microconidia, chlamydospores, and hyphae .

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Epidermophyton

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Microsporum canis

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Trichophyton mentagrophytes

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Trichophyton rubrum

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Trichophyton rubrum on

dermatophyte test medium

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Malassezia furfur on a lipid rich

medium

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Aspergillus niger

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Culture tube method

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Culture tube method

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Microsporum canis

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Microsporum canis

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Epidermophyton floccosum

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Trichophyton rubrum

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Epidermophyton floccosum

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Aspergillus fumigatus

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Aspergillus

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