Cutaneous Mycoses Flashcards
• Are caused by fungi that infect the keratinized tissues - skin, hair, and nails (and feathers); affect humans and animals.
Cutaneous Mycoses
Cutaneous mycoses
• Agents:
_________
- Microsporum, Trichophyton, Epidermophyton, etc.
__________
- most often Candida species
Dermatophytic fungi - dermatophytosis/tinea/ringworm
Nondermatophytic fungi - dermatomycosis
Parasitize the nonliving, cornified integument, secrete keratinases (keratinophilic, keratinolytic); its metabolic products induce an allergic & inflammatory eczematous response in the host
Cutaneous mycoses
• 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
Dermatophytes
• Asexual forms:
• Sexual forms:
hyaline, septate, branching hyphae, macroconidia, microconidia, or arthroconidia (infectious fragments of hyphae)
ascospores; teleomorphic genus used to be Arthroderma.
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
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
is still considered the gold standard for diagnosing dermatophytosis. (Best if in tandem
with DNA sequence analysis.)
Fungal culture
Dermatophytes
• 3 Classifications:
*Geophilic (soil, environment)
*Zoophilic (animals)
* Anthropophilic (humans)
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
• 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,
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
Epidermophyton floccosum.
Humans
Tinea cruris
Trichophyton digitale
Humans
Tinea pedis
Trichophyton schoenleinii
Humans
Tinea capitis
favosa
Dermatophytes:
• Live on animals (asymptomatic carriers) but species have evolved to live on non-human animals.
Zoophilic
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
Zoophilic
• Human infections:
• Usually with significant inflammation & shorter course of infection
M. canis
T. mentagrophytes
T. verrucosum
• 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
• Etiologic agent of tinea corporis/tinea capitis:
Nannizia gypsea (formerly Microsporum gypseum)
• 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
Clinical features:
Scalp hair infection
Tinea capitis
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
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 -
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
