Cutaneous and Subcutaneous Mycoses PART1 Flashcards
Cutaneous Mycoses:
Microsporum
Trichophyton
Epidermophyton
Subcutaneous Mycoses
Mycetoma
Chromoblastomycosis
Phaeohyphomycosis
Sporotrichosis
-Most common fungal infections of humans. Usually referred to as tinea (Latin for “worm” or “ringworm”)
Cutaneous Mycoses/ TINEA
Ringworm of the body
Tinea corporis
Ringworm of the groin or “jock itch”
Tinea cruris
Ringworm of the scalp and hair
Tinea capitis
Ringworm of the beard
Tinea barbae
Ringworm of the nail
Tinea unguium
-Members of this genus are widely
distributed and are the most
important and common causes of
infections of the feet and nails
- Commonly seen in adult infections
- Most cosmopolitan species are
anthropophilic or “human loving”
- Hairs infected with organisms do not fluorescence under the UV light of a Woods lamp
Trichophyton
Calcofluor white/KOH preparations reveal the presence of hyaline septate hyphae or arthroconidia
Trichophyton
-Infected hairs may reveal the hair shaft to be filled with masses of large arthroconidia (4-7 um) in chains (endothrix infection). Infected hairs that show external masses of spores that
ensheaths the hair shaft (ectothrix infection)
Trichophyton spp.
infected hairs reveal hyphae and air spaces within the shaft
Trichophyton Shoenleinii
Trichophyton spp. Initial growth must be subcultured onto _____ to induce sporulation
cornmeal agar or potato dextrose agar
are the most common species recovered in the clinical laboratory
T. rubrum and T. mentagrophytes
is slow-growing, produces a flat/heaped-up
colony, generally WHITE TO REDDISH, with cottony or velvety surface
Trichophyton rubrum
Characteristic cherry-red color best observed on the reverse side of the colony (after 3-4 weeks of incubation)
T. rubrum
T. rubrum Two types of colonies may be produced:
fluffy and granular
microconidia are uncommon in most of the
fluffy strains and more common in the granular strains. Microconidia occur as small, teardrop-shaped conidia often borne laterally along the sides of the hyphae
- Macroconidia are less common; they appear in granular strains as thin-walled, smooth-walled, multi celled, cigar-shaped conidia with three to eight septa
- has no specific nutritional requirements
- Does not perforate hair in vitro or produce
urease
T. rubrum
produce two distinct colonial forms:
downy variety recovered from patients with tinea pedis and the granular variety recovered from lesions acquired by contact with animals
T. mentagrophytes
- Rapidly growing colonies
- Appear white to cream-colored or yellow
- Cottony or downy
- Coarsely granular to powdery
- May produce a few spherical microconidia
- Reverse side of colony is usually ROSE BROWN, occasionally orange to deep red (may be confused for T. rubrum)
T. mentagrophytes
-colonies sporulate freely;
- microconidia in grapelike clusters and thin-walled, smooth walled, cigar-shaped macroconidia measuring 6 × 20 μm to 8 × 50 μm, with two to five septa
- Macroconidia characteristically exhibit a definite narrow attachment to their base.
- Spiral hyphae may be found in one third of the isolates recovered.
T. mentagrophytes
- produce urease within 2 to 3 days after
inoculation onto Christensen’s urea agar - Perforate hair unlike T. rubrum
T. mentagrophytes
Responsible for an epidemic form of tinea capitis that commonly occurs in children
T. tonsurans
causes a low-grade superficial lesion of varying
severity and produces circular, scaly patches of
alopecia (loss of hair)
T. tonsurans
The stubs of hair remain in the epidermis of the scalp after the brittle hairs have broken off, which may give the typical “black dot” ringworm appearance
T. tonsurans
-Cultures of develop slowly and are typically buff to brown, wrinkled, and suedelike in appearance.
- colony surface shows radial folds and often develops a craterlike depression in the center with deep fissures
T. tonsurans
Reverse side of the colony is YELLOWISH TO REDDISH BROWN. Numerous microconidia with flat bases are produced on
the sides of hyphae.
T. tonsurans
- With age, the microconidia tend to become pleomorphic, are swollen to elongated, and are referred to as balloon forms
T. tonsurans
-T. tonsurans growth is greatly enhanced by the presence of ____in casein agar
thiamine or inositol
Colonies are small, heaped, and folded; occasionally they are flat and disk-shaped.
T. verrucosum
At first, they are glabrous and waxy, with a short aerial mycelium. Colonies range from GRAY TO WAXLIKE TO BRIGHT YELLOW, The reverse of the colony most often is
nonpigmented but may be yellow
T. verrucosum
causes a severe type of infection called favus;
characterized by the formation of yellowish
cup-shaped crusts, or scutulae on the scalp
T. schoenleinii
A distinctive invasion of the infected hair, the favic type, is demonstrated by the presence of large, inverted cones of hyphae and arthroconidia at the base of the hair follicle and branching hyphaethroughout the length of the hair shaft
T. schoenleinii
Slow grower (30 days or longer)
- produces a WHITE TO LIGHT GRAY colony with a waxy surface
T. schoenleinii
-Colonies have an irregular border consisting mostly of submerged hyphae, which tend to crack the agar.
- The surface of the colony is usually nonpigmented or tan, furrowed, and irregularly folded
T. schoenleinii
The reverse side of the colony is usually tan or
nonpigmented.
T. schoenleinii
The hyphae tend to become knobby and club-shaped at the terminal ends, with the production of many short lateral and terminal branches
T. schoenleinii
All strains may be grown in a vitamin-free
medium and grow equally well at room temperature or at 35°C to 37°C.
T. schoenleinii
- Very slow growing
- Beginning as cone-shaped, cream-colored, glabrous colonies
T. violaceum
-Later these become heaped up, verrucous (warty), violet to purple, and waxy in consistency.
- Colonies may often be described as “port wine” in color.
- The reverse side of the colony is purple or
nonpigmented.
T. violaceum
- microconidia and macroconidia generally are not present; only sterile, distorted hyphae and
chlamydoconidia are found
T. violaceum
- Growth of T. violaceum is enhanced on media
containing
thiamine
-Early detection medium (Kane and Smitka) = 4% casein and 0.5% yeast extract
- organism is recognized by its early hydrolysis of casein and very slow growth rate
T. verrucosum
Very slow growing
T. violaceum
Slow grower (30 days or longer)
T. schoenleinii
Slow grower (14-30 days)
T. verrucosum
