Mycological examination

Professor Danka Švecová, MD, PhD.

Handbook of dermatovenerology

for practical lessons

Mycological examination

• The fungi may cause skin, hair, and nail disease, and intrinsicorgans disease

• Three groups of fungi :

Dermatophytes

Yeast

Molds

Mycological examination

DERMATOPHYTES

• Antropophilic dermatophytes – the main host is man (Trichophyton rubrum, T.mentagrophytes var.interdigitale, Epidermophyton floccosum, T.schoenleini, Microsporumaudouinii, T.tonsurans, T.violaceum)

• Zoophilic dermatophytes- the main host are various animals(T. mentagrophytes var.granulosum, T.verrucosum, M.canis)

• Geophilic dermatophytes- the main host is soil (M.gypseum)

Mycological examination

YEAST

• Candida albicans and other species of Candida (C.tropicalis, C.pseudotropicalis, C.quilliermondii)

MOLDS

• few species of numerous molds cause superficial mycosis(Scopulariopsis brevicaulis)

Mycological examination

• Diagnosis of mycotic disease → clinical picture; case history

• The clinical diagnosis should be confirmed by mycological identification of the fungi

• Microscopic examination

• Culture of fungi

• Examination with Wood lamp

• Histopathological examination (PAS staining)

• Confirmation of hair affinity by dermatophytes in vitro

• Recovery of keratinophylic fungi from soil

Tinea – caused by dermatophyte fungi

Candidiasis – caused by yeast fungi

Removing of the pathologic material

• Pathologic material - scales of the skin from the border of the lesion; the top of blisters; affected hair (broken, dim); nails (dyscolored,

hyperkeratotic).

• Other patologic material membranous cover of the mucous membrane;

intrinsic organs: blood, sputum,

liquor, urine,stool, pus, etc.

Removing of the pathologic material: Tinea

• Removing of the scales, hair, nails

• The lesion is cleared with aetheralcohol or 70% etanol; border of lesion is scraped with sterile scalpel

• Affected hair is pulled out with tweezers

• Affected nail is snipped off with scissors, forceps, file

• Pathological material is collected in sterile tube

Removing of the pathologic material: Yeast infection

• Pathological material from mucous membrane or from skin affected with yeast –sterile cotton swab soaked with physiologic saline

• Other material – blood, sputum as for microbiological examination

Microscopic examination : Tinea• Scales, nails→ crumbled to small pieces in

the test tube with sterile scalpel

• Slide + drop of potassium hydroxide 15% (nails 30%) → covered with a coverslip →placed in a damp atmosphere (Petri dish with moist absorbent paper) for 1 h →maceration of the horny material

• Or short heating over a burner (without boiling)

• Or addition of 40% DMSO –quick preparation

• Staining with Parker´s ink,or cotton blue

Microscopic examination: Tinea

Dermatophyte

• Presence of hyphae and spores

• All dermatophytes possess the same characteristic → species identification cannot be performed using microscope examination

Ectothrix position → the hyphae and spores lie outside the cuticle → typical for zoophilic dermatophyte and Microsporum auduinii(exception!!!)

Dermatophyte infection of hair

Dermatophyte infection of hair

Endothrix position → the hyphae and spores penetrate the hair shaft → typical for antropophilic dermatophyte with hair keratin affinity

Microscopic examination: yeast infection

Candidiasis

Lactophenol appearenceof pseudohyphae and blastospores (circular to oval yeast cells), budding cells

Culture of fungi

Sabouraud ´s glucose agar

• streptomycin → to prevent bacterial growth

• cycloheximide → to prevent molds growth

Dermatophyte

▪ Room temperature: 2-4 weeks

Yeast

▪ Room temperature

▪ 37°C : 1 week

Culture of fungi

Trichophyton rubrum

Wood lamp examination

• Lamp of longwave UV radiation (UVA 365 nm)

• Dark room

• Distinct fluorescence

• Light green →Tinea causedby Microsporum audouinii, M.canis

• Golden-yellow →Pityriasisversicolor

• Brilliant-red →Erythrasma