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MYCOLOGY

MYCOLOGY. FUNGI. Uni or multicellular organisms Eukaryotes Defined nuclei Cell walls of carbohydrate and chitin Saprophytic or parasitic Vegetative and sexual reproduction. SAPROPHYTIC FUNGI, CHANTERELLES. FUNGI IN VETERINARY MEDICINE. Dermatophytes: grow on skin and hair

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MYCOLOGY

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  1. MYCOLOGY

  2. FUNGI • Uni or multicellular organisms • Eukaryotes • Defined nuclei • Cell walls of carbohydrate and chitin • Saprophytic or parasitic • Vegetative and sexual reproduction

  3. SAPROPHYTIC FUNGI, CHANTERELLES

  4. FUNGI IN VETERINARY MEDICINE • Dermatophytes: grow on skin and hair • Yeasts: grow on mucous surfaces and in the body • Systemic infection: hyphae and yeasts

  5. FUNGI IN VETERINARY MEDICINE • Fungal products: Beneficial (antibiotics) Harmful (mycotoxins) • Fungal spoilage: animal foods, forages, animal products such as meat and hides

  6. Terminology • Ascospore: asexual spore produced in a sac-like structure called an ascus • Arthospores: asexual spore formed by the disarticulation of the mycelium • Chlamydospores: thick-walled, resistant spores formed by the direct differentiation of hyphae • Conidia: asexual spore formed from hyphae by budding or septal division • Conidiophore: a stalk-like branch from the mycelium in which conidia develop either singly or in numbers

  7. Terminology • Germ tubes: tube-like structures produced by germinating spores • Hyphae: the filaments that composed the body of a fungus • Macroconidia: large multinucleate spores • Microconidia: single-celled spores • Mycelium: a mat made up of interwining thread-like hyphae • Pseudohyphae: filaments composed of elongated budding cells that have failed to detach

  8. FUNGAL SPOILAGE, SILAGE

  9. MUCOR • Hyphae 5-15m • Grow fast in culture • Greyish white aerial mycelium • Mycotic abortion • Rumen ulcers • Systemic mycosis in young or debilitated animals • Meat spoilage

  10. MUCOR IN CULTURE

  11. MUCOR ON MEAT. NOTE SPORANGIA

  12. YEASTS • Single cells • Reproduce vegetatively by budding • Occasionally form pseudomycelium • Sexual reproduction by forming ascospores within cell • Candida, Malassezia, Cryptococcus, Histoplasma

  13. CANDIDA • 3-6 m, oval cells • Gram positive • Pseudohyphae • Germ tubes • Chlamydospores • Grows at 37C on Sabouraud’s dextrose agar • Creamy white 2mm colonies

  14. CANDIDA COLONIES

  15. PSEUDOHYPHAE, CANDIDA

  16. CANDIDA ALBICANS IN ANIMAL DISEASE • Cattle • Mycotic abortion • Rumenal infections • Mastitis • Dogs-chronic enteritis and vaginitis/vulvitis • Birds-crop infections, enteritis

  17. CRYPTOCOCCUS • C. neoformans • Nasal cavity of cats with chronic rhinitis • Encapsulated • 20 m total

  18. CRYPTOCOCCUS IN INDIAN INK TO SHOW CAPSULE

  19. DERMATOPHYTES • Septate branching hyphae • Digest keratin • Microconidia, arthrospores, macroconidia • Grow on Sabouraud’s within 7-14 days at 28C • Identify by surface appearance and colour of underside • Confirm by shape of macroconidia

  20. MICROCONIDIA

  21. MACROCONIDIA

  22. MICROSPORUM • Ringworm in man and animals • Microconidia en thyrse (along sides of hyphae) • May fluoresce under Wood’s light

  23. M. CANIS • Ringworm in cats and dogs transmissible to man • Grows on hair with arthrospores ectothrix • Microconidia relatively common • Macroconidia elliptical with up to 14 divisions, rare on isolation • Fluoresces • Colonies smooth surface, yellow underside

  24. M. CANIS

  25. M. CANIS ON MAN

  26. TRICHOPHYTON • Ringworm in man and animals • Club-shaped macroconidia • Spiral hyphae • No fluorescence

  27. SPECIES OF TRICHOPHYTON • T. verrucosum • Ringworm in cattle transmissible to man • Abundant chlamydospores • Large spore ectothrix on hair • Colonies slow growing • Deep in agar • T. equinum horse • T. gallinae fowl

  28. T. VERRUCOSUM, CALF

  29. ASPERGILLUS • Septate branching hyphae • Sporing heads or conidia in oxygen • Conidiophore • Aspergillus may have sexual stages • Use colonial appearance, size and details of conidiophore to identify

  30. ASPERGILLUS FUMIGATUS • On food • On fodder • Spores infect young non-immune or immunosuppressed animals • Grows best on Sabouraud’s at 24-28C • Star shaped colonies • Green-blue with sporing heads

  31. ASPERGILLUS FUMIGATUS

  32. ASPERGILLUS CONIDIOPHORE

  33. ASPERGILLUS IN AIRSACS

  34. BOVINE LUNG, ASPERGILLOSIS

  35. MYCOTOXINS • Aspergillus flavus produces aflatoxin • Aflatoxin is carcinogenic • Claviceps purpurea (ergot) produces alkaloids • Fusarium culmorum produces zearelenone toxin • Penicillium rubrum produces rubratoxin • Penicillium viridicatum produces Ochratoxin A

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