Dermatophytes

Introduction
Classification
Pathogenesis
Clinical types
Lab diagnosis
Prevention

1. DERMATOPHYTES Ankur vashishtha Subharti university Meerut

2. Lesson Plan Introduction Classification Pathogenesis Clinical types Lab diagnosis Prevention

3. DERMATOPHYTOSES Dermatophytoses ( tinea or ringworm ) is the most common superficial mycosis affecting skin, hair, and nails. These are closely related keratinophilic fungi, which are capable to invade keratinized tissues of skin and its appendages and are correctively known as Dermatophytes .

4. Characteristics of dermatophytes Filamentous fungi, digest keratin. Does not invade living tissues. They are incapable of penetrating subcutaneous tissue.

5. Morphological classification Dermatophytes are hyaline septate molds with more than hundred species described. These are divided into three main anamorphic genera depending on their morphological characteristics, according to shape and site infections. Trichophyton :- pencil shaped, infect skin, hair, nails (24 species ) T. rubrum T. m entagrophytes T. schoenleinii T. tonsurans T. violaceum

6. Morphological classification 2. Microsporum :- spindle shaped, infect skin and hair. (16 species) M. audouinii M. canis M. equinum M. gypseum 3 . Epidermophyton :- Club shaped, infect skin and nails. (2 species) E. floccosum E. stockdaleae

7. Ecological classification Depending on the usual habitat (Humans, animals, and soil). Anthrophilic :- infected Humans. Zoophilic :- infect animals as well as birds. Geophilic :- frequently isolated from soil.

8. Classification of dermatophytes based on their usual habitat Habitat Trichophyton Microsporum Epidermophyton Anthropophilic T. rubrum T. mentagrophytes T. schoenleinii T. tonsurans T. violaceum M. audouinii E. floccosum Zoophilic T.equinum T. verrucosum M. canis M. equinum Geophilic T.ajelloi M. gypseum E. stockdaleae

9. PATHOGENESIS Mode of infection :- Acquired by direct contact with soil, animals or humans infected with fungal spores. Predisposing factors – moist humid skin and tight ill – fitting underclothing. Skin: grow in a centrifugal pattern in the stratum corneum annular or ring-shaped pruritic scaly skin lesions with central clearing and raised edges. Nails: invade nails through lateral or superficial nail plates and then spread throughout the nails. Hair shaft: invade the hair shaft or may be found surrounding it. Hairs become brittle and areas of alopecia may appear. *Males more commonly infected as progesterone is inhibitory to dermatophyte growth.

10. PATHOGENESIS Incubation period :- 1 to 2 weeks. Anthropophilic dermatophytes :- commonest, cause relatively mild and chronic lesions but respond poorly to treatment. Geophilic and zoophilic species :- less adapted to human, produce more acute inflammatory response and severe infections; but they tend to resolve more quickly.

11. CLINICAL types of dermatophytoses Tinea capitis Tinea corporis Tinea pedis (Athlete foot) Tinea cruris (jock itch) Tinea barbae Tinea faciei Tinea imbricate Tinea unguium (nail plate infection) Tinea manuum

12. CLINICAL types Tinea capitis Infection of the scalp. (various types) Kerion :- Painful inflammatory reaction producing boggy lesions on scalp Favus :- Cup like crust ( scutula ) forms around the infected hair follicle with minimle hair shaft involvement Ectothrix :- Arthrospore formation occurs on the surface of hair shaft Endothrix :- Arthrospore formation occurs within the hair completely filling hair shaft. Tinea corporis Infection of the non hairy skin of the body (trunk and limbs)

13. CLINICAL types Tinea pedis (Athlete foot) Infect first the webs between the toes, then spread to the sole in a “moccasin” pattern. Tinea cruris (jock itch) Infection of the groin area

14. CLINICAL types Tinea barbae Infection of the beard and moustache area of face Tinea facie Infection of the non-bearded area of face

15. CLINICAL types Tinea imbricate Concentric lesions of the skin Tinea unguium (nail plate infection ) Infection of nail beds Tinea manuum Infection of the palmar aspect of hands

16. ID reaction Id reaction is secondary eruption occurring in sensitized tinea patients because of circulation of allergenic products from primary site of infection. Frequently found in patients with absence of delayed reaction to dermatophytic antigens ( i.e. trichophytin ). Two main types of id reaction:- Lichen scrofulosorum -like :- commonly associated with tinea capitis in children. Pompholyx -like :- lesions are frequently found on sides and flexor aspects of fingers and palms in patients with tinea pedis .

17. Laboratory diagnosis Woods Lamps Examination:- Positive for various Microsporum species & T richophyton schoenleinii . Fluorescence is due to the presence of pteridine pigment in cell wall. Fluorescence seen under wood’s lamp Microorganism Fluorescence Color Microsporum audouinii Bright – green Microsporum canis Bright – green Microsporum ferrugineum Blue – green Microsporum distortum Blue – green Microsporum gypseum Dull – yellow Trichophyton s choenleinii Dull – green Malassezia furfur Golden – yellow

18. Laboratory diagnosis 1.) Skin scraping 2.) Hair plucks 3.) Nail clipping from the active margin of the lesions. Specimen Collection:-

19. Transportation of specimen Transportation :- Moisture free paper * When scrapings are to be sent through post, they should be folded in thick black paper.

20. Direct Examination KOH mount :- branching septate hyaline mycelia, which frequently show arthrospore production. Hair- arthroconidia on the surface of shaft ( ectothrix ) or within the shaft ( endothrix ). Septate hyaline hyphae and arthospores of dermatophytes

21. Culture Medium- Sabouraud dextrose agar (SDA) containing cycloheximide and incubated at 25 °C, 30 °C and 37 °C for 4 weeks. Potato dextrose agar – better sporulation (useful for the production of pigment). * Colonies appear in 10 days to 3 weeks, depending on the organism. Dermatophytes test Medium (DTM) :- used for presumptive identification of dermatophytes from fungal or bacterial contaminants found prevalent in cutaneous lesions. Incubation at 25 °C.

22. Identification Macroscopic appearance of the colonies :- R ate of growth Texture Pigmentation Colony topography

23. Colony morphology of dermatophytes Trichophytpon Species , B. Microsporum species , C. Epidermophyton species Macroscopic (colony) appearance of various dermatophytes on SDA . A b c

24. Microscopic identification Microscopic appearance :- the colony are teased and LPCB mount is made to demonstrate the hyphae and spore ( conidia). Conidia :- two types Microconidia :- small unicellular Macroconidia :- Multicellular, septate Special hyphae :- hyphae such as spiral hyphae, racquet hyphae and favic chandeliers.

25. Distribution of conidia of Dermatophytes Dermatophytes Macroconidia Microconidia Trichophyton Rare, thin – walled , smooth Abundant Microsporum Numerous, thick – walled, rough Rare Epidermophyton Numerous, smooth – walled Absent

26. LPCB tease mounts Trichophytpon Species , B. Microsporum Species , C. Epidermophyton Species Microscopic appearance of various dermatophytes species (LPCB mount ). b c A

27. MORPHOLOGICAL CHARACTERSTICS Dermatophytes Colony morphology Microscopic morphology T. rubrum Velvety, red pigment on reverse Tear-drop microconidia , pencil-shaped macroconidia T. mentagrophytes White to tan, cottony or powdery, pigment variable Clusters of microconidia cigar-shaped Microconidia with terminal rat-tail filament T. schoenleinii Smooth, waxy, brownish Hyphal swellings, chlamydospores , favic chandelier T. violaceum Very slow growing, waxy, violet to purple pigment Distorted hyphae , conidia rare M. audouinii Velvety, brownish, slow growning Thick-walled chlamydospores , conidia rare and irregular

28. MORPHOLOGICAL CHARACTERSTICS Dermatophytes Colony morphology Microscopic morphology M. canis Cottony, orange pigment on reverse Abudant , thick-walled spindle-shaped macroconidia with up to 15 septa M.Gypseum Powdery, buff- colored Abudant , thin-walled macroconidia with 4-6 septa E.floccosum Yellowish-green, powdery Club-shaped macroconidia in clustrs

29. Biochemical test Urease test :- Trichophyton mentagrophytes is urease positive Urease Positive Urease Negative

30. Other methods of diagnosis Hair perforation test :- fungi pierce hair producing wedge – shaped perforations. Positive :- Trichophyton mentagrophytes and Microsporum canis .

31. Other methods of diagnosis Molecular methods :- PCR Skin test :- detects hypersensitivity to trichophytin

32. Treatment Oral terbinafine or itraconazole are the drug of choice for treatment of dermatophytosis . Duration :- depends on the affected site (1 – 2 weeks for skin lesions, 6 weeks for hair infection, 3 months for onychomycosis ) They can be given as pulse therapy. Alternative :- oral griseofulvin and ketoconazole Topical lotion :- whitfield ointment or tolnaftate

33. References Textbook of Medical Mycology, Jagdish Chander . Essentials of Medical Microbiology, Apurba Sankar Sastry .

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