7. 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.
8. 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.).
9. Dermatophytes Geophilic species - e.g., M. gypseum, T. ajelloi Zoophilic species - e.g., M. canis, T. verrucosum Anthropophilic species - e.g., M. audounii, T. tonsurans)
10. a. Microsporum - skin, hair (scalp) - children, rarely in adults - spontaneous remission b. Epidermophyton - skin, nails c. Trichophyton - hair (scalp), skin & nails - chronic
12. 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 Trichophytonmentagrophytes
15. Tinea corporis MOT: direct contact; fomites; autoinnoculation normally resolves itself in several months. (T. rubrum – relapse) TX: topical agent containing tolnaftate, ketoconazole, miconazole.
16. 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).
18. 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
20. 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.
21. Tinea cruris 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
22. 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.
25. Tinea pedis All forms are pruritic EA: T. rubrum(chronic infections) E. floccosum(acute & spontaneously resolves)
26. 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
29. Tinea barbae Ringworm of the bearded areas of the neck postularfolliculitis Common among men who work with cattles EA: T. verrucosum & T. mentagrophytes
30. Tinea barbae Kerions: boggy inflammation/spongy swelling Alopecia is also common in untreated infections
33. Two forms of T. unguium: Leukonychiamycotica /superficial white onychomycosis - invasion of fungus restricted on patches or pits on surface of the toenail. Invasive subungualdermatophytosis- lateral or distal edges first involved, followed by invasion of nail plates by dermatophytes. Tinea unguium
34. Tinea unguium Most commonly caused by T. rubrum, then E. floccosumor otherTrichophyton spp. Resistant to treatment Rarely resolves spontaneously.
37. Tinea capitis Ringworm of the scalp, eyebrows and eyelashes Fungus grows into hair follicle and hair shaft Caused by species of Microsporumand Trichophyton.
40. Tinea capitis Ectothrix infection - fragmentation of mycelium into conidia around the hair shaft or just beneath the cuticle.
41. Tinea capitis Caused by M. audouinii, M. canis, M. ferrugineum, T. mentagrophytes, T. verrucosum and T. megninii.
42. Tinea capitis “gray patch T. capitis" ectothrix disease common in children usually not associated with inflammation.
43.
44. 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.
45. Tinea favosa (favus) Leads to scarring and alopecia “mousy odor” Caused by T. schoenleinii
46. 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.
47. Methods: 1. Direct Microscopy Not sensitive Useful in more severe conditions KOH (10% & 20%)
48. 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
49. Emmon’s modification of SabouraudDextrose Agar (SDA); orSDA with 4% glucose incorporate chloramphenicol or gentamicin and cycloheximide thiamine will enhance growth of dermatophytes esp. Trichophytonverrucosum (Nutritional Studies) Dermatophyte Test medium (DTM) screening medium (w/ phenol red)
52. Microsporumgypseum 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
61. Trichophyton species 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).
67. Colony: fluffy white with Port burgundy wine or venous blood underside. When intensely pigmented in culture the color is reminiscent Trichophytonrubrum
68.
69. Trichophytontonsurans 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
70.
71. Trichophytontonsurans 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.
Dermatophytes ("skin plants“). Tinea: char. by advancing , serpiginous nature of the lesion
dermatophyte crosses non-host lines (e.g., from an animal species to man).Dermatophytes are NOT inhibited by CYCLOHEXIMIDE
Evolutionary transition from a saprophytic to a parasitic lifestyle. Some have strict association with….Geophilic species – “earth-loving” (e.g., M. gypseum, T. ajelloi)Zoophilic species - keratin-utilizing on living animal host (e.g., M. canis, T. verrucosum)Anthropophilic species - keratin-utilizing on humans hosts (e.g., M. audounii, T. tonsurans)
Microsporum -skin, hair (scalp), rarely nails Epidermophyton - adults, rarely childrenTrichophyton - both children & adults - chronic
Tinea unguium (onychomycosis) Tineas or “ringworms”
Fomites: rugs and carpets (fomites). T.metagrophytes (w/ red pigment (colony); urease production in 3 - 5 days; V-shape penetration on hair-baiting test)T. rubrum (intense red pigment is more enhanced by culture on PFA or CMA w/ 1% DEXTROSE; no urease; grows outside hair shaft w/o penetration.)
Fomites: rugs and carpets (fomites). T.metagrophytes (w/ red pigment (colony); urease production in 3 - 5 days; V-shape penetration on hair-baiting test)T. rubrum (intense red pigment is more enhanced by culture on PFA or CMA w/ 1% DEXTROSE; no urease; grows outside hair shaft w/o penetration.)
Tinea imbricata -subtype of Tinea corporis, concentric layers of lesions
Ringworm of the groin (“jock itch”) Infection seen on scrotum and inner thigh, the penis is usually not infected.
Epidermophyton floccosum(usually associated with epidemics because resistant arthroconidia in skin scales can survive for years on rugs, shower stalls, locker room floors *Predisposing factors: persistent perspiration, high humidity, irritation of skin from clothes, such as tight fitting underwear or athletic supporters or other pre-existing diseases, such as diabetes and obesity.
Diagnosis If lesion "weep", it is likely caused by a yeast, such as, Candida albicans, and not by a dermatophyte, especially if infections are seen in a woman.
“Athlete’s foot”
“barber’s itch” – Tinea barbae
“barber’s itch” – Tinea barbaeKerions: boggy inflammation- due to deep infection of hair follicles
KOH (10% & 20%)May be added with DMSO(to increase penetration of stain into tissues)
DTM: contains phenol red (dermatophytes produce alkaline metabolites resulting to change in the color from yellow to reddish- orange or red)
Macronidia: Ellipsoidal to fussiform (cucumber shape) with thick, rough walls
Epidermophytonfloccosum:Only one pathogenic specie in this genus.
