MICROBIOLOGY LECTURE M3 – Cutaneous Mycoses Lecture and Notes by Evelina N. Lagamayo M.D. USTMED ’07 Sec C – AsM CUTANEOUS MYCOSES
CHARACTERISTICS
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PATHOGENESIS
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“keratophilic fungi” – use keratin as a substrate keratinases
Schematic Diagram of Tissues Colonized by Dermatophytes
diseases of the skin, hair, and nails involves the keratinized layers of the skin and its appendages clinical manifestation: tinea or ringworm o Ex. Tinea pedis, tinea ungium,tinea corporis
ETIOLOGY : Dermatophytes
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Classification in anamorphic state: 1. Microsporum 2. Trichophyton 3. Epidermophyton
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Teleomorphic state of Microsporum and Trichophyton is genus Arthroderma
ECOLOGY AND EPIDEMIOLOGY
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Classification according to ecological niche:
A. Stratum corneum; B. Ectothrix hair infection; C. Entothrix hair infection; D. favic hair infection
1. 2.
LABORATORY DIAGNOSIS
3.
Geophilic dermatophytes- isolated from the soil Zoophilic dermatophytes- associtation with domestic and wild animals and birds Anthropophilic dermatophytes- associated with humans and their habitats
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Asexual State of Selected Dermatophytes
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KOH: 10%, 20% Except: T. schoenleinii causing favus: o infected hair have a waxy mass of hyphal elements(scutulum) surrounding the base of the hair follicle at the scalp line. o microscopic exam: degenerated hyphal elements coursing throughout the hairshaft Fungal Culture : SDA w/ cylcoheximide, chloramphenicol o conidia:
o
macroconidia multicellular
–
large
and
microconidia - small and unicellular spiral hyphae, chlamydospores, nodular bodies, racquet hyphae and chandeliers
TREATMENT
1.
Azoles – miconazole, clotrimazole, econazole (topical) Mechanism of action: o interferes with cytochrome P-450dependent enzyme system s at the the demethylation step from lanosterol to ergosterol
2.
Griseofulvin - fungistatic, affects the microtubular system of fungi - interferes with the mitotic spindle and cytoplasmic microtubules oral route
Classification of Dermatophytes According to Ecological Niche
Fungal infection of endothrix infection
the
hair,
Fungal infection ectothrix infection
of
the
hair,
General Characteristics of Macroconidia and Microconidia of Dermatophytes
KOH preparation of skin scrapings. Dermatophytes showing septate hyphae intertwined among epithelial cells.(Phase contrast500X)
KOH smear of skin scrapings. M. furfur showing spherical yeast cells (A) and short hyphal fragments(B)
-finKOH smear of sputum. Rhizopus spp. Showing fragmented portions of septate hyphae of varying size
Scotch tape preparation with lactophenol cotton blue or aniline blue
Performance of a wet mount, showing agar positioned under coverslip before using pressure to disperse growth
Microslide culture, inoculation of agar plug
Numerous small, spherical microconidia(A) contrasted with a large, elongated macroconidium(B)
M. canis, showing several spindleshaped , thick-walled, multicelled macroconidia
M. gypseum, showing ellipsoidal, multicelled macroconidia
E. floccosum, showing numerous smooth, multiseptate, thin-walled macroconidia that appear clubshaped
M. canis, macroconidia
M. gypseum, macroconidia
Epidermophyton macroconidia
Trichophyton chandelier
floccosum,
schoenleinii,
favic
T. mentagrophytes, and microconidia
showing
macroconidia
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