INSTITUTE OF HEALTH TECHNOLOGY, DHAKADepartment of Laboratory Medicine

BSc in Health Technology (Laboratory)- 1st Year

MYCOLOGY Lecture No. 04 (Cutaneous Mycoses)

By

Sk. MIZANUR RAHMANLecturer, Mycology

MS in Biotechnology & Genetic Engineering (UODA)MS in Microbiology (SUB)

Cutaneous Mycoses

oDermatophytosis - "ringworm" disease of the nails, hair, and/or stratum corneum of the skin caused by fungi called dermatophytes. oDermatomycosis - more general name for any skin disease caused by a fungus.

Cutaneous mycoses

• Infection of the skin, hair or nails caused by a group of keratinophilic fungi, called dermatophytes

• DERMATOPHYTOSIS (=Tinea = Ringworm)

extend deeper into the epidermis, as well as invasive hair and nail diseases.

DERMATOPHYTES

• Digest keratin by their keratinases• Resistant to cycloheximide• Classified into three groups depending

on their usual habitat

Cutaneous mycoses

• Keratophilic – use keratin as subject to live ( parasites)

• Keratinases- invade only keratinized layers

DERMATOPHYTOSIS

ClassificationThree Groups/Types:• Clinical• Etiological• Ecological

Clinical DermatophytosisClinical Classification & Manifestations

• Infection is named according to the anatomic location involved:

- Tinea corporis: small lesions occurring anywhere on the body

- Tinea pedis :"athlete's foot". Infection of toe webs and soles of feet.

- Tinea unguium (onychomycosis) :nails. Clipped and used for culture

- Tinea capitis : head. Frequently found in children

Tinea barbae: ringworm of the bearded areas of the face and neck.

Cutaneous InfectionsInfections of skin and its appendages (nails, hair); 20 species of dermatophytes cause ringworm.

Etiology of Dermatophytes

Etiology (3 Genera) • Trichophyton• Microsporum• Epidermophyton

• Trichophyton - infections on skin, hair, and nails.

• Microsporum - infections on skin and hair (not the cause of TINEA UNGUIUM)

• Epidermophyton - infections on skin and nails (not the cause of TINEA CAPITIS)

Etiology (3 Genera)

Trichophyton (19 species)

• Hair • Skin• Nails

Trichophyton • For Trichophyton species - infections on hair follow one of

the 4 patterns. – Ectothrix - more or less parallel rows of arthrospores

produced on surface of hair. • 1. Small-spored ectothrix (arthrospores are < 5 mm

in diameter) - caused by T. mentagrophytes or T. rubrum (rare). Spores are about the same size as those produced by Aspergillus. • 2. Large-spored ectothrix (arthrospores are 5- 10

mm in diameter) - caused by T. verrucosum. – Endothrix - growth inside hair shaft only! • 3. "Black-dot" endothrix (hair stubs filled with

arthrospores) - caused by T. tonsurans or T. violaceum. • 4. "Favus hair" endothrix (honeycomb pattern

of damage seen on surface of hair shaft) - caused by T. schoenleinii.

Trichophyton species

Trichophyton rubrum

Causes a chronic infection in patients with a cell-mediated immune defect.

• Skin• Hair

Microsporum (13 species)

Microsporum species

Thick wall, spindle shape, multicellular

Microsporum canis

Most common etiologic agent of tinea

• Skin• Nails

Epidermophyton floccosum

Epidermophyton floccosum

Bifurcated hyphae with multiple, smooth, club shaped macroconidia (2-4 cells)

Ecology of Dermatophytes

To determine the source of infection

• Anthropophilic• Zoophilic• Geophilic

Anthropophilic

• Associated with humans only. Person -to-person transmission through contaminated objects (comb, hat, etc.) • e.g., M. audounii, T. tonsurans

Zoophilic

• Associated with animals. Direct transmission to humans by close contact with animals.• e.g., M. canis, T. verrucosum

Geophilic

• Usually found in soil (soil saprophytes). Transmitted to humans by direct exposure.•e.g., M. gypseum, T. ajelloi.

DERMATOPHYTOSISDiagnosis

I. ClinicalAppearanceWood’s lamp (UV, 365 nm) II. Lab A. Direct microscopic examination(10-25% KOH)

DERMATOPHYTOSISDiagnosis

B. Culture• Mycobiotic agar • Sabouraud dextrose agar • Selective media – containing cycloheximide and

chlorampenicolincubate at 25 C.• Identification based on the conidia

Diagnosis

• Diagnosis is based upon: 1. Anatomical site infected 2. Type of lesion 3. Examination with a Woods lamp (366 A°) 4. Examination of KOH-treated skin scales from the infected area 5. Culture of the organism (not too important)

Dermatophytes Culture

Dermatophyte Culture

Black collection card

Ringworm culture

General characteristics of Macroconidia and Microconidia of Dermatophytes

Genus Macroconidia Microconidia

Microsporum Numerous, thick walled,rough

Rare

Epidermophyton Numerous, smooth walled

Absent

Trichophyton Rare,thin walled, smooth

Abundant

Microsporum

Trichophyton

Epidermophyton floccusom