Mycology Lec3cutaneous

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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