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Information about Dermatophytosis

Published on March 9, 2014

Author: Raghunathreddy


Dermatophytoses: Dermatophytoses Dr. Pendru Raghunath Reddy Assistant Professor of Microbiology Dr. VRK Women’s Medical College PowerPoint Presentation: Dermatophytoses or cutaneous mycoses are diseases of the skin, hair and nail Generally called ringworm infections and tinea These infections are caused by a homogenous group of closely related fungi known as dermatophytes These dermatophytes infect only superficial keratinised structures such as skin, hair and nail but not deeper tissues PowerPoint Presentation: The most important dermatophytes that cause infection in humans are classified into three genera Trichophyton - infections on skin, hair, and nails. Microsporum - infections on skin and hair (not the cause of TINEA UNGUIUM) Epidermophyton - infections on skin and nails (not the cause of TINEA CAPITIS) PowerPoint Presentation: The dermatophytes on the basis of their natural habitat and host preferences can be classified into following groups Anthropophilic species Zoophilic species Geophilic species PowerPoint Presentation:  Anthropophilic Associated with humans only Person -to-person transmission through contaminated objects (fallen hairs, desquamated epithelium, combs, hat, towel etc.) Examples: Trichophyton rubrum , Microsporum audouinii and Epidermophyton floccosum PowerPoint Presentation:  Zoophilic Associated with animals Direct transmission to humans by close contact with domestic animals (cat and dog) and occasionally wild animals Examples: Trichophyton violaceum and Microsporum canis PowerPoint Presentation:  Geophilic These are saprophytic fungi found in soil or in dead organic substances They occasionally cause infection in humans and animals Examples: Microsporum gypseum and Trichophyton ajelloi PowerPoint Presentation: Dermatophytes usually grow only on keratinised skin and its appendages and do not penetrate the living tissue In some infected persons, hypersensitivity to fungus antigen may cause secondary eruptions such as vesicles on the finger This reaction is known as dermatophytid (Id) reaction This reaction occurs as a result of hypersensitivity response to circulating fungal antigen, and these lesions do not contain any fungal hyphae Dermatophytid (Id) reaction: Dermatophytid (Id) r eaction PowerPoint Presentation:  Clinical features The skin infections caused by dermatophytes are chronic infections of the skin often found in the warm humid areas of the body Typical ringworm lesions are circular , dry, erythematous , scaly and itchy which have an inflamed border containing papules and vesicles surrounding a clear area of relatively normal skin These lesions are associated with variable degrees of scaling and inflammation Nails are thickened, deformed, friable, discolored , subungual debris accumulation Dermatophytoses clinical classification: Dermatophytoses clinical c lassification Infection is named according to the anatomic location involved : a. Tinea barbae e. Tinea pedis ( Athlete’s foot) b. Tinea corporis f . Tinea manuum c. Tinea capitis g . Tinea unguium d. Tinea cruris (Jock itch) Transmission: Transmission Close human contact Sharing clothes, combs, brushes, towels, bedsheets ... (Indirect ) Animal-to-human contact ( Zoophilic ) PowerPoint Presentation:  Tinea capitis This is the infection of the shaft of scalp hairs and presents as the following clinical types Inflammatory – Kerion , favus Non-inflammatory – Black dot, Ectothrix and Endothrix The infected hairs in tinea capitis appear dull and grey The base of hair shaft as well as hair follicles is involved There is breakage of hair at follicular orifice which creates patches of alopecia with black dots of broken hairs Tinea capitis: Tinea capitis Ectothrix: Ectothrix The arthrospores appear as mosaic sheath around hair or as chains on surface of hair shaft The cuticle of hair remains intact Hyphae invade hair shafts at mid follicle and as hair grows out of follicle, hyphae burst out of shaft and cover hair surface with mass of small arthrospores Caused by T. mentagrophytes , M. canis , M. audouinii , M. gypseum and T. verrucosum PowerPoint Presentation: Endothrix Hyphae form arthrospores within hair shaft, which is severely weakened Cuticle of hair is usually destroyed The arthrospores are 3-4 µm in diameter and are observed in chains filling inside shortened hair stubs Caused by T. schoenleinii , T. tonsurans and T. violaceum T. rubrum cause both ectothrix as well as endothrix infections PowerPoint Presentation:  Tinea corporis This is disease of glabrous (non-hairy) skin of body and may result from extension of infection from scalp, groin or beard Characterised by erythematous scaly lesions, annular, sharply marginated plaques with raised border which may be single, multiple or confluent Tinea corporis: Tinea corporis PowerPoint Presentation:  Tinea Pedis This is the infection of plantar aspect of foot, toes and interdigital web spaces It is frequently seen among individuals wearing shoes for long hours and popularly known as Athlete’s Foot In toe webs, scaling, fissuring, maceration and erythema may be associated with an itching or burning sensation Due to maceration and peeling, cracks appear which are prone to secondary bacterial infections When infection becomes chronic, sole becomes hyperkeratotic and is often covered with fine scales Tinea Pedis: Tinea Pedis PowerPoint Presentation:  Tinea Barbae Infection of beard and moustache areas of face with invasion of coarse hairs Also called as barber’s itch There are erythematous patches on face which show scaling Tinea Barbae:  Tinea Barbae Tinea Faciei: Tinea Faciei Dermatophytic infection of skin that occurs on non-bearded regions of face PowerPoint Presentation:  Tinea Cruris Dermatophytic infection of groin Involves perineum, scrotum and perianal area and may spread to inner third of buttock and occasionally to thigh The appearance of Tinea Cruris can be seen in other intertriginous areas such as axilla and around umblicus of obese patients PowerPoint Presentation:  Tinea Manuum Dermatophyte infection of skin of palmar aspect of hands The most common clinical manifestation is diffuse hyperkeratosis of palms and fingers PowerPoint Presentation:  Tinea Unguium Dermatophyte infection of nail plates and is largely a disease of adults It begins under leading free edge of nail plate or along lateral nail fold and may continue until entire nail plate and nail bed are infected There is accumulation of subungual debris in an opaque, chalky or yellowish thickened nail Tinea Unguium: Tinea Unguium PowerPoint Presentation: Laboratory diagnosis Specimens Scrapings of the skin and nail as well as short lengths of hair plucked from the scalp. Scrapings are taken from the edges of ringworm lesions Direct microscopic examination KOH wetmount Branching hyaline septate (non-pigmented) hyphae is considered positive for fungi; spores may also be seen PowerPoint Presentation:  Wood’s lamp In suspected Tinea capitis , plucked hair is examined by using wood’s lamp Infected hair will be fluorescent (yellow green) PowerPoint Presentation:  Culture Species identification is possible only by culture examination Sabouraud’s dextrose agar containing chloramphenicol and cycloheximide The plates incubated aerobically at 25-30 0 C for upto 21 days Identification of dermatophytes in the laboratory is by examing the macroscopic characteristics of the fungal colonies (rate of growth, texture, colour on the observe and reverse) PowerPoint Presentation:  Microscopic examination Trichophyton Microconidia are abundant and arranged in clusters along the hyphae Macroconidia are relatively scanty generally elongated, with blunt ends and have distinctive shapes in different species Some species possess special hyphal characters such as spiral hyphae , raquet mycelium and favic chandeliers PowerPoint Presentation:  Microsporum Microconidia are relatively scanty and not distinctive Macroconidia, the predominant spore form, are large, multicellular , spindle shaped structures, borne singly on the ends of hyphae Microsporum species infect the hair and skin but usually not the nails PowerPoint Presentation:  Epidermophyton Colonies are powdery and greenish yellow Microconidia are absent Macroconidia are multicellular , pear-shaped and typically arranged in clusters Epidermophyton attacks the skin and nails but not the hair Epidermophyton floccosum: Epidermophyton floccosum PowerPoint Presentation:  Treatment This is by using topical preparations (ointments or gels) containing azoles ( miconazole , clotrimazole , econazole ) or terbinafine Oral preparations of griseofulvin , azoles ( ketoconazole , itraconazole ) or terbinafine

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