Dermatophytosis, raghu
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Transcript of Dermatophytosis, raghu
Dermatophytoses
Dr. Pendru Raghunath ReddyAssistant Professor of MicrobiologyDr. VRK Women’s Medical College
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
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)
The dermatophytes on the basis of their natural habitat andhost preferences can be classified into following groups
1. Anthropophilic species
2. Zoophilic species
3. Geophilic species
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
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
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
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
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
• Infection is named according to the anatomic location involved:
a. Tinea barbae e. Tinea pedis (Athlete’s foot)
b. Tinea corporis f. Tinea manuumc. Tinea capitis g. Tinea unguiumd. Tinea cruris
(Jock itch)
Transmission
• Close human contact
• Sharing clothes, combs, brushes, towels, bedsheets... (Indirect)
• Animal-to-human contact (Zoophilic)
Tinea capitis
This is the infection of the shaft of scalp hairs and presents as the following clinical types
a) Inflammatory – Kerion, favusb) 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
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
EndothrixHyphae 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
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 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 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 Faciei
Dermatophytic infection of skin that occurs on non-bearded regions of face
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
Tinea Manuum
Dermatophyte infection of skin of palmar aspect of hands
The most common clinical manifestation is diffuse hyperkeratosis of palms and fingers
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
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
Wood’s lamp
In suspected Tinea capitis, plucked hair is examined by using wood’s lamp
Infected hair will be fluorescent (yellow green)
Culture
Species identification is possible only by culture examination
Sabouraud’s dextrose agar containing chloramphenicol and cycloheximide
The plates incubated aerobically at 25-300C 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)
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
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
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
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