Cutaneous Mycoses Dermatophytosis Lecture Four

Cutaneous Mycoses (dermatophytosis)

General futures Involves skin, nail, and hair Known as ringworm or tinea Keratinized layer are infected Fungi known as dermatophytes Infection range form mild to sever Depend on host state and fungal species Resist cycloheximide

Etiologic agents

Over hundred species described Only 40 are valid less associated with human diseases Grouping of dermatophytes Anamorphic state (asexual phase)Three genera Depend on sporulation

Etiologic agents cont.

Morphologic futuresNutritional requirementsMicrosporum, Trichophyton and

Epidermophyton

Natural habitat

Anthropophilic (humans) Zoophilic (animal) Geophilic (soil) All of them can cause diseases in human

Natural habitat Cont.

ANTROPOPHILIC Trichophyton rubrum...

GEOPHILIC Microsporum gypseum...

ZOOPHILIC Microsporum canis: cats and dogs Microsporum nanum: swine Trichophyton

verrucosum: horse and swine…

DERMATOPHYTOSISClinical Classification Infection is named according to the

anatomic location involveda. Tinea barbae e. Tinea pedis

(Athlete’s foot)b. Tinea corporis f. Tinea manuumc. Tinea capitis g. Tinea unguiumd. Tinea cruris

(Jock itch)

Images of dermatophytes infections

T. pedis

Kerion

T. manuumOnychomycosis

Pathogenesis and ImmunityContact and traumaMoistureCrowded living conditionsCellular immunodeficiency

(chronic inf.)Re-infection is possible (but,

larger inoculum is needed, the course is shorter )

Clinical manifestation

Tinea capitis (scalp)Common in childrenTypical lesions," kerion”, scarring,

“alopecia”Favus (Tinea favosa)Debris, yellow cup shaped crustScutulaCicatricial alopeciaT. schoenleinii

Clinical manifestation Cont.

Skin Circular, dry, erythematous, scaly,

itchy lesions Nail Thickened, deformed, friable,

discoloured nails, subungual debris accumulation

DERMATOPHYTOSISTransmissionClose human contactSharing clothes, combs, brushes,

towels, bed sheets. (Indirect)Animal-to-human contact

(Zoophilic)

Human contact Animal contact

Dermatophytes Diagnosis

I. ClinicalAppearanceWood lamp (UV, 365 nm) II. Lab Direct microscopic examination

(10-25% KOH)Ectothrix/endothrix/favus hair

Dermatophytes Diagnosis images

Clinical

KOHEdothrix Ectothrix

Hair invasion by Dermatophytes

Wood lamp

Dermatophytes Diagnosis

CultureMycobiotic agar Sabouraud dextrose agarShould contain antibiotic $

actidione

T. rub rum

M. canis T. vilaceum

Dermatophytes Identification Colony characteristicsMicroscopic morphology genus Macroconidium

Microconidium Microsporum---- fusiform---------------(+) Epidermophyton clavate-----------------(-) Trichophyton-- - (few) cylindrical/ --- --

(+) clavate/fusiform single, in clusters

Microscopic morphology of Microscopic morphology of dermatophytesdermatophytes

Examples

Microsporum canis T rubrum

E. floccosum Chlamydospores

Treatment

Topical Miconazole, clotrimazole econazole, terbinafine...OralGriseofulvinKetaconazole ItraconazoleTerbinafine