Mycology Lecture Notes - Cutaneous Mycoses

INSTITUTE OF HEALTH TECHNOLOGY, DHAKA Department of Laboratory Medicine BSc in Health Technology (Laboratory) - 1 st Year MYCOLOGY Lecture No. 04 ( Cutaneous Mycoses) By Sk. MIZANUR RAHMAN Lecturer, Mycology MS in Biotechnology & Genetic Engineering (UODA) MS in Microbiology (SUB) Cut...

INSTITUTE OF HEALTH TECHNOLOGY, DHAKA Department of Laboratory Medicine BSc in Health Technology (Laboratory) - 1 st Year MYCOLOGY Lecture No. 04 ( Cutaneous Mycoses) By Sk. MIZANUR RAHMAN Lecturer, Mycology MS in Biotechnology & Genetic Engineering (UODA) MS in Microbiology (SUB) Cutaneous Mycoses o Dermatophytosis - "ringworm" disease of the nails, hair, and/or stratum corneum of the skin caused by fungi called dermatophytes . o Dermatomycosis - 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 Classification Three Groups/Types: • Clinical • Etiological • Ecological Clinical Dermatophytosis Clinical 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 Infections Infections 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 . DERMATOPHYTOSIS Diagnosis I. Clinical Appearance Wood’s lamp (UV, 365 nm) II. Lab A. Direct microscopic examination (10 - 25% KOH) DERMATOPHYTOSIS Diagnosis B. Culture • Mycobiotic agar • Sabouraud dextrose agar • Selective media – containing cycloheximide and chlorampenicol  incubate 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