lec.3 and 4 Diseases Resulting from Fungi and Yeasts

Diseases Resulting from Fungi and Yeasts

Dermatophytes

Frequency of species

Clinical manifestations of ringworm infections are called different names on basis of location of infection sites
tinea capitis - ringworm infection of the head, scalp, eyebrows, eyelashes tinea corporis - ringworm infection of the body (smooth skin) tinea cruris - ringworm infection of the groin (jock itch) tinea unguium - ringworm infection of the nails tinea barbae - ringworm infection of the beard tinea manuum - ringworm infection of the hand tinea pedis - ringworm infection of the foot (athlete's foot)

Major sources of ringworm infection

Tinea Capitis
Occurs chiefly in children – less commonly in infants and adultsBoys more frequently than girlsTinea capitis can be caused by all pathogenic dermatophytes except Epidermophyton floccosumClinical presentation of Tinea capitis include :Non-inflammatory & inflammatory.

Non-inflammatory

Gray-patch M. audouinii infections present as the classic form Characterized by multiple scaly lesions, stubs of broken hair, and a minimal inflammatory response Occasionally eyelids, and eyelashes are involved


Tinea Capitis
Non-Inflammatory type“Black dot” ringworm, caused by T. tonsurans & occasionally T. violaceum presents as multiple areas of alopecia studded with black dots representing infected hairs broken off at or below the surface of the scalp

Black dot ringworm caused by Trichophyton tonsurans

InflammatoryKerion

Usually caused by M. canis Can be caused by T. mentagrophytes, M. gypsem, or T. verrucosum M. canis infection begins as scaly, erythematous, papular eruptions with loose and broken-off hairs, followed by various degrees of inflammation

Kerion

A localized spot accompanied by pronounced swelling, with developing bogginess and induration exuding pus A delayed type hypersensitivity reaction to fungal elements With extensive lesions fever, pain, and regional lymphadenopathy may occur Permanent alopecia can occur.


Kerion: inflammatory of tinea capitis caused by Microsporum canis or Trichophyton mentagrophytes

Permanent scarring alopecia post kerion

Inflammatory (Favus)
Rare , appears mainly on the scalp On scalp, concave sulfur-yellow crusts from around loose, wiry hairs , called scutulae, Scutula have a distinctive mousy odor Scaring and permanent alopecia

Favus of scalp showing scutulae

Types of hair invaders
. Ectothrix invasion is characterised by the development of arthroconidia on the outside of the hair shaft. The cuticle of the hair is destroyed and infected hairs usually fluoresce a bright greenish yellow colour under Wood's ultraviolet light. Common agents include M. canis, M. gypseum, T. mentagrophyte and T. verrucosum


Endothrix hair invasion is characterised by the development of arthroconidia within the hair shaft do not fluoresce. The cuticle of the hair remains. All endothrix producing agents are anthropophilic e.g T. tonsurans and T. violaceum.

Ectothrix and Endothrix

Fluorescing hair (under Wood's lamp) is seen in dogs and cats infected with some dermatophytes

Culture

Final and exact identification of causative fungusSeveral infected hairs are placed on Sabouraud’s glucose agar(4 weeks) or Dermatophyte Test Medium (DTM)-for 2 weeks

Treatment

Griseofulvin 10 mg/kg/day, is the daily dose recommended for children Tx should continue for 2-4 months, or for at least 2 weeks after a negative microscopic and culture examinations are obtained. Terbinafine tab. systemic steroids, to minimize scarring, can be given simultaneously Selenium sulfide shampoo or ketaconazole shampoo three times weekly can be used as adjunctive therapy to oral antifungal agents


Tinea Corporis(Tinea Circinata)
Includes all superficial dermatophyte infections of the skin other than those involving the scalp, beard, face, hands, feet, and groin Sites of prediliction are neck, upper and lower extremities, and trunk Can be caused by any dermatophyte

Characteristics of lesion

Characterized by one or more circular, sharply circumcsribed, slightly erythematous, dry, scaly, usually hypopigmented patches Lesions may be slightly elevated, particularly at the border, where they are more inflamed and scaly than at the central part


Progressive central clearing produces annular outlines that give them the name “ringworm

Tinea corporis: note sharp margin and central clearing

Etiology-Tinea Corporis
Various organisms may cause this type of fungal infection Microsporum canis, T. rubrum, T. mentagrophytes- T. rubrum is is the most common dermatophyte In children, M. canis is the cause of the moist type of tinea circinata

Epidemiology

Tinea corporis is frequently seen in children-particularly those exposed to animals with ringworm(M. canis), especially cats, dogs and less commonly, horses and cattle In adults excessive perspiration is the most common factor Incidence is especially high in hot, humid areas of the world



Treatment-Tinea Corporis
Griseofulvin,at 500 mg per day Terbinafine at 250 mg/day for two weeks Itraconazole 200 mg B.I.D. for one week Fluconazole 150 mg once/week for 4 weeks Creams are more effective than lotions in topical TX

Tinea Cruris

jock itch Most common in men On upper and inner thighs Begins as a small erythematous and scaling or vesicular and crusted patch Spreads peripherally and partly clears in the center Characterized by its curved, well-defined border, especially at lower edge Border may have vesicles, pustules, or papules May extend downward on thighs and backward on the perineum or anus

Tinea cruris in a woman

Etiology-Tinea Cruris
T. mentagrophytes & E. floccosum & T. rubrum are usual cause Infection with Candida albicans may closely resemble tinea cruris (satellate lesion )

Keep as dry as possible by wearing underclothing and trousers Plain talcum powder or antifungal powders are helpful Specific topical and oral tx is same as that described under tinea corporis

Tinea pedis

Popularly called athlete’s footMost common fungal disease (by far)Most commonly the third toe web is involvedPt usually seeks relief because of itchingSweat on soles and in between has a high pH, is a good culture medium for the fungus

Etiology

Trichophyton mentagrophytes produces an acutely inflammatory condition Trichophyton rubrum produces non-inflammatory condition(a moccasin or sandel appearance)


Tinea pedis showing interdigital scalping T. mentagrophytes

Dermatophytosof the soles Trichophyton mantagrophytes

Trichophyton rubrum
T. rubrum causes the majority of cases Produces a relatively non-inflammatory type of dermatophytosis characterized by a dull erythema and prnounced scaling involving the entire sole and sides of feet Producing a moccasin or sandel appearance

Prophylaxis

Hyperhidrosis is a predisposing factor Dry toes after bathing Dryness is essential if re-infection is to be avoided Use good antiseptic powder on feet after bathing-particularly between toes e.g., Tolnaftate powder. Plain talc, may be dusted into socks and shoes to keep feet dry

Treatment

Topical Azol soaks macerated lesion with solutions such aluminum acetate, Anti-inflammatory effects of corticosteroids are markedly beneficial Topical antibiotic ointments, such as gentamicin, effective against gram-negative organisms Keratolytic agents, such as salicylic acid

Onychomycosis(Tinea Ungium)

Fungal infection of nail Represents up to 30% of diagnosed superficial fungal infections Etiologic agents are species: Epidermophyton,, and Trichophyton fungi Nail plate become friable, yellow, or white as in trichophyton infections May also be caused by C. albicans and here nail plate remains hard .

Treatment

Terbinafine 250 mg/day for 6 weeks (fingernails) 12 weeks for toenailsItraconazole, 200 mg twice daily for 1 week of each month for 2 months (fingernails) & 3 months for toenailsFluconazole experience is less-but 150 –300 mg once weekly for 6-12 monthsGriseofulvin? Therapy continued until nails are clinically normalLow success rates 15-30% for toenails and 50-70% for fingernails


Candidiasis
Candida proliferates in outer layers of the stratum corneum where horny cells are desquamating It does not attack hair, It is largly an opportunisitic organism, able to behave as a pathogen mainly in impaired immune status, or in body folds Moisture promotes its growth, in moist lip corners

Diagnosis

Demonstration of the pathogenic yeast C. albicans establishes the diagnosisUnder microscope KOH prep may show spores and pseudomyceliumOn gram stain yeast forms are dense, gram-positive, ovoid bodies, 2-5 um in diameterIn culture C. albicans should be differentiated from other forms of Candida that are only rarely pathogenicCulture on Sabouraud’s glucose agar shows a growth of creamy, grayish, moist colonies in about 4 days

Candidiasis

KOH mount from infant with thrush showing pseudohyphae and yeast forms

Topical Anticandidal Agents

Azole derivative which include, clotrimazole ,econazole , ketaconazole (Nizoral), miconazole , oxiconazole ,sulconazole, nystatin, Topical amphotericin B lotion Terbinafine has been reported to be less active against Candidaspecies by some authors

Diseases by C. albicans

Thrush Esophagitis Cutaneous Candidiasis Genital Yeast Infections Deep Candidiasis

Oral Candidiasis (BabiesThrush)

Mucous membrane of the mouth may be involved in healthy newborn & marasmic infant Newborn infection may be acquired from contact with vaginal tract of mother Grayish white membranous plaques are found on surface Base of plaques are moist, reddish, and macerated

Adult thrush

Infection of the oral tissues with Candida albicans; often an opportunistic infection in immunodepleted patient. Papillae of tongue are atrophied, surface is smooth, glazed, and bright red Frequently infection extends onto angles of the mouth to form perleche (seen in elderly, debilitated, and malnourished pts, and diabetics

Perleche

Candidal Vulvovaginitis
C. albicans is a common inhabitant of vaginal tract May cause severe pruritus, irritation, and extreme burning Labia may be erythemtous, moist, and macerated and cervix hyperemic, swollen, and eroded, showing small vesicles on its surface Vaginal discharge is not usually profuse but is frequently thick and tenacious

Risk factors

Due to disruption of normal microbiota May develop during in pregnancy, in diabetes, or secondary to therapy with a broad- spectrum antibiotic , I.U.C.D Recurrent vulvovaginal candidiasis has been associated with long-term tamoxifen, oral contraceptive pills.

Candidal Intertrigo

Pruritic intertriginous eruptions caused by C. albicans may arise between folds of genitals; in groins or armpits; between buttocks; under large pendulous breasts; under overhanging abdominal folds; or in umbilicusPinkish intertriginous moist patches are surrounded by a thin macerated epidermis (“collarette” scale)

Pseudo Diaper Rash

In infants, C. albicans infection may start in perianal region and spread over entire area Dermatits is enhanced by maceration produced by wet diapers Scaly macules and vesicles with maceration in involved areas cause burning, pruritis, and extreme discomfort



Diagnosis may be suspected by finding involvement of folds and occurrence of many small erythematous desquamating “satellite” or “daughter” lesions scattered around edges

Perianal Candidiasis

When pruritis ani is present C.albicans should be suspected Frequently entire GI tract is involved Can be precipitated by oral antibiotic therapy Perianal dermatitis with erythema, oozing, and maceration is present Psychogenic etiology is more common than is candidiasis

Candidal Paronychia

Chronic inflammation of nail fold produces occasional discharge of thin pus, gradual thickening and brownish discoloration of nail plates, and development of pronounced transverse ridges Mostly finger nails are affected frequently occur in person whose hands in water or who handle moist objects

Onychomycosis caused by Candida albicans in mucocutaneous candidiasis

Intertrdigital candidal infection
Usually white, thick and does not peel off freely On feet fourth interspace is most often involved Areas are apt to be multiple Clinically indistinguishable from tinea pedis Dx made by culture Tx is with topical anticandidal preparations

Candida fingerweb erosion：related to fatness , occupation etc.

THE END
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