Cutaneous Mycoses Flashcards by Kyra Catedral

• Are caused by fungi that infect the keratinized tissues - skin, hair, and nails (and feathers); affect humans and animals.

Cutaneous Mycoses

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Cutaneous mycoses

• Agents:
_________
- Microsporum, Trichophyton, Epidermophyton, etc.

__________
- most often Candida species

Dermatophytic fungi - dermatophytosis/tinea/ringworm

Nondermatophytic fungi - dermatomycosis

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Parasitize the nonliving, cornified integument, secrete keratinases (keratinophilic, keratinolytic); its metabolic products induce an allergic & inflammatory eczematous response in the host

Cutaneous mycoses

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• Restricted to nonviable skin, hair, or nails, unable to grow at 37C, or in the presence of serum

• Many species have particular keratinases, elastases, and other enzymes enabling them to be quite host-specific.

Dermatophytes

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Dermatophytes

• Asexual forms:
• Sexual forms:

hyaline, septate, branching hyphae, macroconidia, microconidia, or arthroconidia (infectious fragments of hyphae)

ascospores; teleomorphic genus used to be Arthroderma.

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Epidemiology
worldwide in distribution, tropical & subtropical regions

some vary in geographic distribution and virulence for humans

acquired from the transfer of_______, or keratinous material directly or indirectly via fomites, contact with contaminated soil, or with infected animals or humans

Dermatophytosis

arthroconidia

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Initiation of dermatophyte infection in skin.
(1) Arthroconidia from environment or other infected host contacts new host’s skin. Adhesion to skin occurs between_____ after contact.
(2) Arthroconidia begins to_____ in the top layer of the epidermis, forming germ tubes.
(3)____ continue to grow within the epidermis
(4) Within 7 days of infection,____ are formed, allowing for the cycle to repeat.

2-6 h

germinate

Hyphae

arthroconidia

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is still considered the gold standard for diagnosing dermatophytosis. (Best if in tandem
with DNA sequence analysis.)

Fungal culture

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Dermatophytes

• 3 Classifications:

*Geophilic (soil, environment)
*Zoophilic (animals)
* Anthropophilic (humans)

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Dermatophytes

cause the greatest number of infections; elicit mild/chronic infections; are adapted to the human physiology & immune system; may be difficult to eradicate

• Anthropophilic species

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• Anthropophilic species

• Agents: TritsEf

• Species have developed preferences for specific locations on the body.

Trichophyton rubrum (most common), Trichophyton interdigitale,
T. tonsurans,
T. schoenleinii
E. floccosum,

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Feet

Scalp

Nails

Beard

Hands

Groin region

Glabrous skin (body)

Tinea pedis (athlete’s foot)

Tinea capitis

Tinea unguuim
(onychomycosis)

Tinea barbae

Tinea manuum

Tinea cruris

Tinea corporis

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Epidermophyton floccosum.
Humans

Tinea cruris

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Trichophyton digitale
Humans

Tinea pedis

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Trichophyton schoenleinii
Humans

Tinea capitis
favosa

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Dermatophytes:
• Live on animals (asymptomatic carriers) but species have evolved to live on non-human animals.

Zoophilic

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Zoophilic

(dogs/cats)

(horses)

(mice, guinea pigs, kangaroos, cats, horses, sheep, rabbits)

(fowls/chickens)

(voles/bats)

(cattle)

(pigs)

Microsporum canis

T. equinum

T. mentagrophytes

Lophophyton gallinae

Nannizzia persicolor

T. verrucosum

N nana

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Zoophilic

• Human infections:
• Usually with significant inflammation & shorter course of infection

M. canis
T. mentagrophytes
T. verrucosum

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• Mainly reside in soil and keratinous debris shed from animals
• rare cause of human/animal infections
• ecologically important
• Transmitted between hosts; are acquired from the environment

Geophilic

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• Etiologic agent of tinea corporis/tinea capitis:

Nannizia gypsea (formerly Microsporum gypseum)

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• Farmers have a higher risk for acquiring this infection.
• Inflammatory response usually more severe
• generally shorter in duration
• signs are similar to dermatological diseases/disorders

Geophilic

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Clinical features:
Scalp hair infection

Tinea capitis

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Tinea capitis

“black dot ringworm”, “, corkscrew hair,” hair shafts break off at the scalp leaving the black dot stubs.

• Endothrix (inside hair shaft)
• T. tonsurans & T. violaceum

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Tinea capitis

“gray-patch ringworm,” circular bald
patches, short hair stubs, broken hair

Kerion rare. Fluoresce a bright
greenish-yellow under UV, 365 nm

• Ectothrix (on hair surface)
• M. audouinii & M. ferrugineum -

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Clinical features: • ***Raised, circular or ring-shaped patches of alopecia with erythema*** and scaling or as more diffusely scattered papules, pustules, or vesicles • i.e. T. tonsurans, T. schoenleinii, N. gypsea

Tinea capitis • Alopecia with erythema

• ***acute inflammation of hair follicles*** & hypersensitivity, raised spongy lesions, usually zoophilic dermatophytes • i.e. M. canis, T. mentagrophytes

Tinea capitis • Kerions

Clinical features: • An acute inflammatory infection of the hair follicle eventually leads to the formation of ***scutula (crusts, cup-shaed flakes)*** around the follicle • Etiologic agent: T. schoenleinii • ***hyphae do not form spores but can be found within the hair shaft.***

Tinea capitis • Favus/Tinea favosa

Clinical features: • Infection of the beard, moustache areas of the face. • Coarse facial hair with an ectothrix pattern - hyphae & arthroconidia cover outside of the hair • Edematous, erythematous lesion • Caused by: T. verrucosum T. mentagrophytes T. rubrum

Tinea barbae (beard)

Clinical features: • Glabrous (nonhairy/smooth) skin • Circular/annular lesions of ringworm, with a clearing, scaly center surrounded by a red advancing border that may be dry or vesicular. Pruritic. • Caused by: T. rubrum (most common) T. tonsurans E. floccosum M. canis N. gypsea

Tinea corporis - Ringworm

- ***a rare form of tinea corporis*** • Nodules, plaques, papules • Dermatophytes penetrate damaged hair follicles causing deep skin infection. • Caused by: T. rubrum • Occasionally by Aspergillus & Phoma

• Majocchi's granuloma (fungal folliculitis)

Clinical features: • Infection of the face, ***resembles tinea corporis.***

Tinea faciei

• Acute/chronic. ***Oval red scaly patches (less in the middle); may present as a kerion (fungal abscess)*** • ***Aggravated by sun exposure;*** infection comes from tinea pedis, tinea unguium, from cats/dogs, cattle • Caused by: T. rubrum T. tonsurans M. canis T. mentagrophytes

Tinea faciei

Clinical features: • Acute inflammatory rash, extending area of peeling, dryness, mild itching (palm); blistering rash, crops with sticky clear fluid, itches & burns • Contact with another site of infection (tinea pedis or tinea cruis), person with tinea, infected soil, contaminated object like towel or gardening tool • Most commonly caused by: T. rubrum (most) M. canis

Tinea manus/Tinea manuum

Clinical features: • Affecting the groin, pubic region, adjacent thigh, acute or chronic asymmetrical rash, erythematous scaling lesion in intertriginous area, pruritic • By scratching from tinea pedis, tinea unguium, contaminated towels or bed sheets • Caused by: T. rubrum E. floccosum

Tinea cruris/jock itch

Clinical features: • Infection on interdigital spaces of feet; acute - itching, red vesicular, ulcerative, moccasin, hyperkeratosis of the sole; chronic - peeling and cracking; most prevalent • Usually males/adolescent/young adults; direct contact with fungus, shared towel, walking barefoot in a public change room • Caused by: T. rubrum T. interdigitale

Tinea pedis/athlete's foot

Clinical features: • Increasingly prevalent with age • Spreads from tinea pedis, less often from tinea manuum • Lateral - white/yellow opaque streak at one side of the nail • Subungual hyperkeratosis - under the nail • Distal - end of the nail lifts up, free edge crumbles • Proximal - yellow spots in the half-moon (lunula) • Complete destruction of the nail • Caused by: T. rubrum T. mentagrophytes

Tinea unguium (onychomycosis)

Clinical features: • Distal or proximal infection • Nondermatophytes: • Molds: Aspergillus spp. Scopulariopsis, Fusarium, Acremonium, Syncephalastrum, Scytalidium, Paecilomyces, Neoscyatalidium, Chaetomium, Onchocola, Alternaria • Yeasts: Candida albicans, rarely non-albicans candida yeasts

Dermatomycosis Onychomycosis

• An allergic rash caused by an inflammatory fungal infection at a distant site (tinea pedis); • Treated with ***topical steroid*** • Scrapings - negative microscopic and culture methods; no fungi present in lesion. May become secondarily infected BADAN with bacteria. ***Trichophytin skin*** test is markedly positive.

Dermatophytid (id)

Dermatophytosis General Measures

• Wear loose-fitting cotton or synthetic clothing to wick moisture away from the skin. • Avoiding sharing garments and towels. • Avoid infected pets and shared bathing facilities. • Regular washing & drying of undergarments, socks, caps. • Prophylactic use of imidazole or tolnaftate powders. • Avoiding occlusive footwear

Dermatophytosis - TREATMENT Tinea capitis:

• Oral administration of ***griseofulvin or terbinafine*** • Frequent shampoos, miconazole cream, or ketoconazole or itraconazole

Dermatophytosis - TREATMENT Tinea corporis, pedis, and other related infections

• Most effective are ***itraconazole and terbinafine; topical - miconazole nitrate, tolnaftate, clotrimazole*** applied 2-4 weeks

Dermatophytosis - TREATMENT Tinea unguium - most difficult to treat; relapses common

• Months of ***oral itraconazole or terbinafine. Surgical removal of nail.*** • Topical imidazole - luliconazole - penetrate the nail plate, potent against dermatophytes and non-dermatophytes

Macroconidia: Numerous, thick walled, rough Microconidia: Rare

Microsporum

Macroconidia: Numerous, smooth walled Microconidia: Absent

Epidermophyton

Macroconidia: Rare, thin walled, smooth Microcondia: Abundant

Trichophyton

Lab test • In_____ preps of skin & nails regardless of the infecting species: • presence of ***branching hyphae or chains of arthroconidia***

KOH

Lab tests In hairs: - ectothrix (dense sheaths of spores around hair); fluoresce - endothrix (arthroconidia inside hairshaft; do not fluoresce except T. schoenleinii.

• Microsporum spp. • T. tonsurans & T. violaceum

Cutaneous mycoses DIAGNOSTIC LABORATORY TESTS Culture • ID of dermatophytes require culture on _______ or _______ or _______ ________ weeks incubation at room temperature; further observation by slide cultures or subculture on a special medium • species identified on the basis of colonial morphology (growth rate, surface texture, and any pigmentation, microscopic morphology (macroconidia, microconidia), and, in some cases, nutritional requirements, biochemical tests.

Inhibitory Mold Agar (IMA) SDA-CC slants DTM - Dermatophyte test medium 01 to 3 weeks

Usually slow growing, ***greenish-brown or khaki-colored with a suede-like surface,*** raised and folded in the center, with a flat periphery & submerged fringe of growth Older cultures may develop white pleomorphic tufts of mycelium • A ***deep yellowish/orange-brown reverse pigment*** is usually present.

Epidermophyton floccosum

Characteristic ***SMOOTH, thin/thick-walled MACROCONIDIA*** (clavate) which are often produced in ***CLUSTERS (1-6 cells)*** growing directly from the hyphae (septate) • Numerous chlamydospores formed in older cultures

Epidermophyton floccosum

MICROCONIDIA ARE NOT PRODUCED.

E floccosum

Surface colonies: flat, spreading, ***white to cream-colored,*** w/ dense cottony surface, some radial grooves. • Reverse pigment: ***bright golden yellow to brownish yellow, (some strains non pigmented)*** • Macroconidia/microconidia often not produced on primary isolation media; need to do subcultures on Lactritmel agar or boiled polished rice grains for sporulation

Microsporum canis

• Macroconidia/microconidia often not produced on primary isolation media; need to do subcultures on ***Lactritmel agar or boiled polished rice grains for sporulation***

Microsporum canis

• Good growth on boiled polished rice grains, yellow pigment

Microsporum canis

Microscopy: numerous ***SPINDLE-SHAPED MACROCONIDIA,*** ***5-15 cells,*** ***VERRUCOSE, THICK-WALLED,*** often have a terminal knob; few pyriform to clavate MICROCONIDIA

M canis

Hair perforation test: Positive in 14 days

M canis

Surface colonies: flat, spreading, suede-like to granular, ***deep cream to tawny-buff to pale cinnamon-colored surface;*** ***many with a central white downy umbo (dome) or a fluffy white tuft & narrow white peripheral border*** • Reverse pigment: yellow-brown, central darker brown spot, some reddish-brown ***Abundant macroconidia & microconidia***

Nannizzia gypsea

MACROCONIDIA - ***symmetrical, ellipsoidal, thin-walled, verrucose, 4- to 6-cells,*** terminal/distal ends are slightly rounded, proximal ends are truncate Microconidia: numerous, clavate-shaped

N gypsea

• Colonies exhibit a spectrum of overlapping characters: • Texture ( ***downy to suede-like to granular*** ) Surface pigmentation ***(white to cream to deep red)*** • Reverse pigmentation ***(colorless to yellowish to yellow-brown to wine red)***

Trichophyton rubrum

•Tinea pedis/onychomycosis: isolates show scanty to moderate numbers of ***SLENDER CLAVATE MICROCONIDIA & NO MACROCONIDIA*** (formerly the "downy strain")

T rubrum

Cases of tinea corporis: isolates show moderate to abundant numbers of ***CLAVATE to PYRIFORM MICROCONIDIA*** & moderate to abundant numbers of thin-walled, ***CIGAR-SHAPED MACROCONIDIA*** (formerly the "granular strain")

Trichophyton rubrum

Cigar shaped macroconidium

Trichophyton rubrum

Colonies show considerable variation: Texture (suede-like to powdery to flat, a raised center or folded, often with radial grooves) Surface pigmentation ***(pale-buff to yellow to dark brown)*** • Reverse pigmentation ***(yellow-brown to reddish-brown to deep mahogany)***

Trichophyton tonsurans

* Hyphae - relatively broad, irregular, much branched, numerous septa • Microconidia - numerous, varying in size & shape, from ***long clavate to broad pyriform borne at right angles to the hypha*** (often remained unstained with LPCB) Macroconidia - very occasional smooth, thin-walled, irregular, clavate (may be present on some cultures); giant microconidia and chlamydospores in older cultures

Trichophyton tonsurans

Trichophyton tonsurans Confirmatory tests: •_______ agar - chlamydospore-like structures in 5 days • Urease _______ in 5 days •______ requirement for growth (Trichophyton agars: T1 negative, T4 positive) _______: positive in 14 days KEY FEATURES: Microscopic morphology, culture characteristics, endothrix invasion, and partial thiamine requirement

Mycosel agar Urease positive Thiamine Hair perforation test

Trichophyton tonsurans Confirmatory tests: • Mycosel agar - chlamydospore-like structures in_____ • Urease positive in____ • Thiamine requirement for growth (Trichophyton agars: T1 negative, T4 positive) Hair perforation test: positive in_____ KEY FEATURES: Microscopic morphology, culture characteristics, endothrix invasion, and partial thiamine requirement

5 days 5 days 14 days

• Colonies: generally flat, white to cream in color, with a powdery to granular surface. • Some cultures: central folding or develop raised central tufts or pleomorphic suede-like to downy areas. • Reverse pigmentation: usually a yellow-brown to reddish-brown color.

Trichophyton mentagrophytes

• Microconidia: numerous single-celled often in clusters, hyaline, smooth-walled, predominantly SPHERICAL to SUBSPHERICAL in shape, occasionally clavate to pyriform • Macroconidia: smooth, thin-walled, clavate, multiseptate

Trichophyton mentagrophytes

• Varying numbers of chlamydospores, SPIRAL HYPHAE, smooth/thin-walled, clavate macroconidia may be present • Subculture: SDA with 5% salt No special nutritional requirement (Trichophyton agars) • Urease positive, 3-5 days • Hair perforation positive, 14 days

Trichophyton mentagrophytes

Cutaneous Mycoses Flashcards

(69 cards)