6 cutaneus myco

Superficial Mycoses

Causative agents:

Malassezia furfurExophiala werneckiiTrichosporon beigelii Piedraia hortae

Cutaneous mycoses (Dermatophytoses)

fungal infections involving the dermis and its appendages

(hair follicles and nails)

o Dermatomycosis  - more general name for any skin disease caused by a fungus.

o Dermatophytosis – mycotic infection of the nails, hair, and/or stratum corneum of the skin caused by dermatophytes.

o Generally called “Ringworms” or o “Tineas” (Latin for ringworms)

Dermatophytes are keratinophilicAll produce septate, hyaline hyphae Infection:

Colonization of the skinSpreads in a centrifugal pattern forming a

ringAffected area varies from patchy scaling to a

toxic eczema-like reaction

Dermatophytoses

Severity depends on

(1) strains or species of fungus involved (2) sensitivity of the host to a particular pathogenic fungus. 

More severe reactions occur when a dermatophyte crosses non-host lines.

Dermatophytoses

Major sources of ringworm infection

Schools, military camps, prisons.

Warm damp areas (e.g., tropics, moisture accumulation in clothing and shoes). 

Animals (e.g., dogs, cats, cattle, poultry, etc.).

Geophilic species - e.g., M. gypseum,

T. ajelloi

Zoophilic species - e.g., M. canis, T. verrucosum

Anthropophilic species -  e.g., M. audounii, T.

tonsurans)

Dermatophytes

a. Microsporum

- skin, hair (scalp)

- children, rarely in adults

- spontaneous remission

b. Epidermophyton

- skin, nails

c. Trichophyton

- hair (scalp), skin & nails

- chronic

Skin:Tinea corporis Tinea crurisTinea manuum Tinea pedisTinea fascie Tinea imbricata

Hairy areas:Tinea capitis Tinea barbae

Nail:Tinea unguium/ onychomycosis

Tineas

Tinea corporis

Ringworm of the body (Generally restricted to stratum corneum of the smooth skin)

Reddened, circular scaly patch with sharp delineated margins (may developing vesicles and postules)

EA: Trichophyton rubrum

Trichophyton mentagrophytes

Tinea corporis

Tinea corporis – body ringworm

Tinea corporis

MOT: direct contact; fomites; autoinnoculation

normally resolves itself in several months. (T. rubrum – relapse)

TX: topical agent containing tolnaftate, ketoconazole, miconazole.

Tinea corporis

vigorous treatment including cleaning of area to remove scales and fungicidal topical applications of ammoniated mercury ointment, 3 % salicylic and sulfuric acid, or tincture of iodine for several weeks.

Widespread tinea corporis and more severe lesions: systemic griseofulvin treatment (about 6 weeks for effective treatment).

Tinea imbricata

Tinea cruris

Ringworm of the groin

Almost exclusively in men

Lesion resemble tinea corporis

Often starts on the scrotum and spread to the groin as dry, itchy lesions

Tinea cruris (“jock itch”)

Tinea cruris

EA: Trichophyton rubrum

Epidermophyton floccosum (usually associated with epidemics)

MOT: Sharing of linens, towels or clothes (Athletes, soldiers, ship crews)

Predisposing factors: persistent perspiration, irritation of skin from clothes, or other pre-existing diseases.

Diagnosis KOH and Culture of dermatophyte from

skin scrapings. If lesion "weep", it is likely caused by a

yeast, such as,  Candida albicans Treatment

Tolnaftate Area is sensitive

Tinea cruris

Tinea pedis

Ringworm of the soles and interdigital areas

men & women are equally affected

More common in adults

Peeling, maceration and fissuring of the skin to fluid-filled vesicles and bullae.

Tinea pedis

Tinea Pedis – Athlete’s Foot Infection

Tinea pedis

All forms are pruritic

EA: T. rubrum (chronic infections)

E. floccosum (acute & spontaneously resolves)

Tinea manuum

Ringworm of the palms and interdigits

Common among patients with tinea pedis

Symptoms generally resemble that of tinea pedis

EA: T. rubrum & T. mentagrophytes

E. floccosum

Tinea manunm

Dermatophytid Reaction

Tinea barbae

Ringworm of the bearded areas of the neck

postular folliculitis

Common among men who work with cattles

EA: T. verrucosum &

T. mentagrophytes

Tinea barbae

Kerions : boggy inflammation/spongy swelling

Alopecia is also common in untreated infections

Tinea barbae

Tinea fascie

Two forms of T. unguium:

Leukonychia mycotica /superficial white onychomycosis - invasion of fungus restricted on patches or pits on surface of the toenail.

Invasive subungual dermatophytosis - lateral or distal edges first involved, followed by invasion of nail plates by dermatophytes.

Tinea unguium

Most commonly caused by T. rubrum, then E. floccosum or otherTrichophyton spp.

Resistant to treatment Rarely resolves spontaneously.

Tinea unguium

Tinea unguium

Tinea Unguium

Tinea capitis

Ringworm of the scalp, eyebrows and eyelashes

Fungus grows into hair follicle and hair shaft

Caused by species of Microsporum and

Trichophyton.

Tinea capitis

Wood's lamp

Subculture any strands of hair that fluoresce

Tinea capitis

Tinea capitis

Ectothrix infection - fragmentation of mycelium into conidia around the hair

shaft or just beneath the cuticle.

Tinea capitis

Caused by M. audouinii, M. canis, M. ferrugineum, T. mentagrophytes, T. verrucosum and T. megninii.

Tinea capitis

“gray patch T. capitis" 

ectothrix disease common in children usually not associated with inflammation.

Tinea capitis

Endothrix infection - arthroconidia formation within the hair shaft. 

caused by T. tonsurans , T. violaceum, T. rubrum, and T. gourvillii. 

Tinea capitis

“Black-dot T. capitis”

Formed as the hair continues to grow, as the conidia in the shafts of the hair appear as black dots

Tinea Capitis

Tinea favosa (favus)

ringworm infection of the scalp (crusty hair)

Characterized by the occurrence of dense masses of mycelium and epithelial debris, which forms yellowish, cup-shaped crusts.

Tinea favosa (favus)

Leads to scarring and alopecia

“mousy odor”

Caused by T. schoenleinii

Diagnosis of Dermatophytoses

Note the symptoms.

Note the kind of tissue attacked

Observe proper collection of the specimen

Keep specimen dry during transport

Microscopic examination of slides of skin scrapings, nail scrapings, and hair. 

Methods:

1. Direct MicroscopyNot sensitiveUseful in more severe conditions

KOH (10% & 20%)

2. Culture

Observe type of colonies

Pigment production: one pigment on the surface of the colony, and another pigment other than black, on the reverse

Emmon’s modification of Sabouraud Dextrose Agar (SDA); or SDA with 4% glucose

incorporate chloramphenicol or gentamicin and cycloheximide

thiamine will enhance growth of dermatophytes esp. Trichophyton verrucosum (Nutritional Studies)

Dermatophyte Test medium (DTM) screening medium (w/ phenol red)

Microsporum species

Microsporum gypseum

Microsporum canis

Microsporum species

Common features:Colony:

Mycelium: white to buffUnderside: yellow to reddish brown

Microsporum gypseum

Colonies are at first white and downy, later become flat and granular with white sterile hyphae at the center

Surface pigment is tan to cinnamon –pink to brown

Reverse is tan to orange-brown or modified cinnamon-pink on PDA

Microsporum gypseum

Macronidia: Ellipsoidal to fusiform with thick, rough walls

Microconidia: Sessile and solitary

Wood’s lamp: Dull-green yellow

Microsporum canis

Macroconidia: Spindle shaped with asymmetrical beaked apex and thick rough walls

Microconidia: Clavate or pyriform

Microsporum canisTeleomorph: Arthroderma otaeMicrosporum canis

Teleomorph: Arthroderma otae

Wood’s lamp: Bright yellow-green Colonies: Yellow pigment on reverse

Epidermophyton species

Epidermophyton floccosum

Tinea unguium, tinea cruris, pedis

Epidermophyton floccosum

Colony:Center of colony may be foldedMycelium: mustard yellow or “khaki”;

suede, gentle folds; slow growerUnderside: yellow-brown or yellow

orange

Epidermophyton floccosumMicroscopic:

attached in multiples (2 – 4/group)Macroconidia = moderately thick , smooth walls

(beaver tails) or paddle-likeClubbed-shaped, 2 – 5 cell macroconidiaSeptate,hyaline hyphae

Epidermophyton floccosum

Microscopic:

Presence of macroconidia in cultures varies and may not help in identification of cultures.

Most common species include: Trichophyton mentagrophytes T. rubrum T. tonsurans T. verrucosum T. violaceum T. schoenleinii T. ajelloi (rare infects humans).

Trichophyton species

Most common dermatophyte on humans and animals.

Microconidia: en grappe

Trichophyton mentagrophytes

Macroconidia: when present, are cigar-shaped.

Spiral hyphae

Trichophyton mentagrophytes

Colony: Texture: deep, cottony; white and downy; pale yellow to tan reverse

Trichophyton mentagrophytes

Trichophyton mentagrophytes

Resistant and persistent

Microconidium: clavate or "teardrop" shape with a broad attachment point of the hyphae.

may develop on sides of macroconidium.

Trichophyton rubrum

Trichophyton rubrum

Colony: fluffy white with Port burgundy wine or venous blood underside. When

intensely pigmented in culture the color is reminiscent

Trichophyton rubrum

Anthropophilic; third most common cause of tinea capitis

Macroconidia: Short blunt , irregular clubs with moderately thick, smooth walls

Microconidia: Truncate of varying shapes; typically numerous

Hyphae are hyaline, septate and often with terminal swellings

Trichophyton tonsurans

Colony: Usually flat and off-white to yellow initially with a powdery texture; wrinkled

Reverse on SDA is yellow-brown to reddish brown

Growth is enhanced by thiamine and inositol.

Trichophyton tonsurans

Associated with cattle ("barn itch")

Causes severe infections in humans on the scalp and beard.

Trichophyton verrucosum

Colony: no pigment to yellow on reverse.

On unenriched media

chains of chlamydoconidia and antler-like hyphae.

On thiamine-enriched media,

produces many small microconidia and occasionally macroconidia

Trichophyton verrucosum

Trichophyton verrucosum

http://www.mycology.adelaide.edu.au/Fungal_Descriptions/Dermatophytes/Trichophyton/verrucosum.html

Endothrix infection of hair.

Trichophyton schoenleinii

Colony: waxy to suede-like; off white in color.

Colony may become convoluted from folds that develop

No conidia (micro- or macro-) even on enriched media .

Trichophyton schoenleinii