Mycological examination Professor Danka Švecová, MD, PhD. Handbook of dermatovenerology for practical lessons
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