1. DEFINITION: Closely related group of fungi that have great affinity to invade the keratinized part of the skin, hair, nail, wool, horn hoof and feathers. They cause ringworm in animals and tinea in humans.

2. Dermatophytes have the ability to utilize keratin as a nutrient source, i.e. they have a unique enzymatic capacity [keratinase]. Other enzymes also secreted by dermato- phytes:elastases and proteinases,which cosidered as virulence factors. 3. The disease process in dermatophytosis (ring worm) is unique for two reasons: Firstly, no living tissue is invaded the keratinized stratum corneum is simply colonized. However, the presence of the fungus and its metabolic products usually induces an allergic and inflammatory eczematous response in the host. 4. Secondly, the dermatophytes are the only fungi that have evolved a dependency on human or animal infection for the survival and dissemination of their species. 5. Most dermayophytes belong to the Fungi imperfecti and are classified in three anamorphic genera: 1. Microsporum 2. Trichophyton 3. Epidermophyton A few species have been placed in the teleo- morphic genus Arthroderma in phylum Ascomycota 6. Dermatophytes are strict aerobes ,most of which grow slowly on standard SDA. Can resist cyclohexamide in the medium. A few require special growth factors, which are supplied by the addition of yeast extract to the SDA. T.equinum needs nicotinic acid, and T.verrucosum needs thiamine and inositol for growth. 7. Macroconidia and miroconidia are produced in culture. The cultures of many dermatophytes are pigmented. Colonial morphology and the type of macro- conidia produced are used for identification. Arthrospores are the infectious forms ,most often associated with tissue invasion by this group of fungi. 8. These resistant forms can remain viable for more than 12 months in suitable environment in buildings. They are released by fragmentation of hyphae in keratinized structures. Dermatophytosis affects many animal species.The disease is a zoonosis and most human infection caused by Microsporum canis contracted from infected cats. Contagious. 9. Dermatophytes can be grouped on the basis of their habitats and the host preferences as: Geophilic Zoophilic Anthropophilic USUAL HABITAT 10. Geophilic dermatophytes Inhabit and replicate in association with decomposing keratinous materials such as hairs or feathers. Animals can acquire infection with geophilic dermatophytes from soil or from contact with infected animals. Some species may cause infections in man following contact with soil, for example: Microsporum gypseum . 11. Zoophilic dermatophytes Zoophilic species are primarily parasitic on animals and infections may be transmitted to humans following contact with the animal host. Zoophilic infections usually elicit a strong host response and on the skin where contact with the infective animal has occurred i.e arms, legs, body or face,for example: 1. Microsporum canis 2. Trichophyton equinum 3. Trichophyton verrucosum 12. Anthropophilic dermatophytes The common anthropophilic species are primarily parasitic on man .They are unable to colonize other animals and they have no other environmental sources. For example: Epidermophyton fluccosum Trichophyton rubrum Trichophyton mentagrophytes 13. Ringworm in animals 14. Ringworm in animals 15. Ringworm in animals 16. Ringworm in animals 17. Ringworm in animals 18. Tinea in humans 19. Tinea in humans 20. Tinea in humans 21. Tinea in humans 22. Direct microscopy of infected materials Skin Scrapings, nail scrapings and epilated hairs should be examined using 10% KOH or calcofluor white mounts. 23. KOH mount of infected skin scales 24. KOH mount of infected nails 25. Hair invasion Hairs treated with KOH should be examined microscopically for the presence of arthro- spores. The arrangement of arthrospores on hair is called ectothrix,which either: 1-Large ectothrix. 2-Small ectothrix. . 26. Hair invasion 1-Large ectothrix,5-8 microns in sparse chains inside and outside of hair such as: M.gypseum,M.nanum,T.equinum 2-Large ectothrix in chains,which include: a-Megaspores type(5-10 microns) e.g T.verrucosum b-Microides type(3-5microns) e.g T.mentagrophytes c-Intermediate types e.g T.rubrum,T.megninii 27. Hair invasion When the arthrospores arranged inside the infected hair, it is typically endothrix,such as: T. violaceum ,T.sodanense. Favic type: special type of endothrix hair invasion in which hyphae are not break up into arthrospores but die and left air spaces.e.g.T. schoenleinii 28. Hair invasion 29. Hair invasion 30. Hair invasion 31. Hair invasion 32. Hair invasion 33. Laboratory diagnosis of dermatophytes A-Sampling: 1-Lesions should be cleaned by soap & water or disinfected with alcohole 70% using a piece of gauze. 2-A specimen of scales,nail or hair should be free from extraneous material such dirt,sebum,ointments,antifungal agents,it should first be removed with an alcowipe. 3-. Using a blunt scalpel, tweezers, or a bone curette, firmly scrape the lesion, particularly at the advancing border(peripheries of the lesions), hair stumps are epilated by forceps. 34. Laboratory diagnosis of dermatophytes 35. Laboratory diagnosis of dermatophytes 5-Suitable material from cats can also be collected on a large sheet of paper by bruching the caot with a clean toothbrush 6-Skin and nail specimens may be scraped directly onto special black cards, which make it easier to see how much material has been collected and provide ideal conditions for transportation to the laboratory. 36. Laboratory diagnosis of dermatophytes 37. Laboratory diagnosis of dermatophytes B-Ultraviolet (Woods light) examination : Hair infected with parasitic Mirosporum spp may be detected by the yellow green fluorescence in ultraviolet light. The Woods light is useful to detect M.canis infection in cats,dogs and other small animals. 38. Laboratory diagnosis of dermatophytes In tinea capitis caused by parasitic Microsporum species(M.canis,M.distortum,M.audouinii& M.ferrugineum) the parasitized hairs are usually but not always fluorescent yellow green. T. schoenleinii gives dull green fluorescence. Fluorescence is dependent on the host animal as well as on the dermatophyte species. The Fluorescence of hair with dermatophyte infections appears to be due to treptophan metabolites. 39. Laboratory diagnosis of dermatophytes D-Isolation of dermatophytes(culturing): 1-Specimens should be inoculated onto primary isolation media, like Sabouraud's dextrose agar containing cycloheximide (actidione) and chloramphenicol,incubated at 26-28C for up to 4 weeks.Isolation of T.verrucosum(cattle ringworm)is favored at 37C. The growth of any dermatophyte is significant. 2-Multiple cultures are recommended whenever a cotamination proplem can be anticipated,i.e it is better to culture each sample onto more than one tube. 40. Laboratory diagnosis of dermatophytes Addition of DMSO permits quick examination often whithout warming. Adition of DMSO or glycerine prevents rapid drying of the fluid,permits observation of the slide for up to 24 or 48 hours. Slides may be ringed with finger nail polish to save for longer peroids. 41. Laboratory diagnosis of dermatophytes 3-Especial growth requirments can be determined Using commercially-available tricophyton agar: T1=control medium(casein basal medium). Other media,produced by adding growth factors to the basal agar such as: T3=containing thiamine & inositol for isolation of T.verrucosum. T4=containing thiamine only for isolation of T.verrucosum. T5=containing nicotinic acid for isolation of T.equinum. 42. Laboratory diagnosis of dermatophytes 4-Dermatophyte test medium(DTM)has been formulated to differentiate dermatophytes from contaminating fungi. Phenol red is used as a pH indicator in this medium. Growth of dermatophytes results in alkaline metabolic products and the color of the medium changes from yellow to red. Other fungal media should be used in conjunction with DTM because some contaminating fungi can induce a color change. 43. Laboratory diagnosis of dermatophytes In addition,the color change in DTM can obscure the characteristic pigmentation required for differentiation of dermatophyte species. A.Dermatophyte Test Medium (DTM) Sterile medium yellow. B. DTM Positive DTM plate on the right showing color change after two day's growth; Microsporum canis 44. Laboratory diagnosis of dermatophytes Identification criteria for isolates: Colonial morphology,texture,pigmentation and growth rate. Microscopic appearance of macroconidia and other structures such as microconidia,spirals,chlamydospores 45. Macroconidia of dermatophytes Trichophyton Microsporum Epidermophyton 46. EPIDERMOPHYTONMICROSPORUMTRICOPHYTON Club shape. Thin to moderately thick wall Fusiform or spindle shape, Thick wall, Rough surface Cylindrical or pencil shape, Smooth thin wall, Rarely present Macroconidia 1-91-151-12Number of septa Usually absentUsually sessile or stalked and arranged singly along the hyphae. More abundant, May be globose, pyriform or clavate. Are borne singly or in group- like clusters Miroconidia 47. Laboratory diagnosis of dermatophytes There are three forms of colonies: a-Membranous form: the aerial mycelium is entirely absent and the vegetative mycelium is in compact masses e.g.T.verrucosum,T.violaceum.. b-Filamentous form: the aerial mycelium is more or less high and dense e.g.M.canis,M.rubrum,E.floccosum. c-Granular-powdery form:characterized by extensive conidia and absence of aerial filaments e.g. T.mentagrophytes,T.equinum. 48. Laboratory diagnosis of dermatophytes The isolated cultures are examined by the following technique: 1-Wet mount technique. 2-Slide culture technique (microculture technique). 3-Cellophane tape preparation. 49. 1-Wet mount preparation 50. 2-Slide culture technique Its a protocol for transferring fungal colonies to a microscope slide. 51. 2-Slide culture technique 52. 2-Slide culture technique 53. 3-Cellophane tape preparation The protocol involves using cellophane tape and a wooden applicator stick. The tape is attached to the applicator stick as a handle and then the tape is touched to the fungal colony and finally, stuck to a slide with a drop of LPCB stain. The cellophane tape remains as part of the mounting. 54. 3-Cellophane tape preparation 55. Microsporum canis 56. T. mentagrophytes 57. T.mentagrophytes 58. T.verrucosum 59. T.verrucosum