Introduction to mycology

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Introduction to mycology

  1. 1. Medical Mycology Introduction to Basics Dr.T.V.Rao MD11/23/2012 Dr.T.V.Rao MD 1
  2. 2. Introduction• Mykes (Greek word) : Mushroom• Fungi are eukaryotic protista; differ from bacteria and other prokaryotes. 1. Cell walls containing chitin (rigidity & support), mannan & other polysaccharides 2. Cytoplasmic membrane contains ergosterols 3. Possess true nuclei with nuclear membrane & paired chromosomes. 4. Divide asexually, sexually or by both 5. Unicellular or multicellular 11/23/2012 Dr.T.V.Rao MD 2
  3. 3. Characteristics of Fungus• Diverse group of chemo heterotrophs – > 90,000 known species• Saprophytes – Digest dead organic matter• Parasites – Obtain nutrients from tissues of organisms• Molds & mushrooms are multicellular• Yeasts are unicellular11/23/2012 Dr.T.V.Rao MD 3
  4. 4. Fungus Everywhere11/23/2012 Dr.T.V.Rao MD 4
  5. 5. How the fungus are nourished• All are chemo heterotrophs• Absorption of nutrients: powerful Exoenzyme• Grow at lower pH-5 than bacteria• Grow in high salt and sugar• Metabolize complex CH2O like lignin in wood-wood rot11/23/2012 Dr.T.V.Rao MD 5
  6. 6. Mycology• Present as saprophytes in soil, decaying plants ,nature.• Eukaryotes• Known before bacteria Botanists• Developing Nations changing trends USA• More serious and even fatal diseases,11/23/2012 Dr.T.V.Rao MD 6
  7. 7. FUNGI (Mycology) Diverse group of heterotrophs. – Many are ecologically important saprophytes (consume dead and decaying matter) – Others are parasites. Most are multicellular, but yeasts are unicellular. Most are aerobes or facultative anaerobes. Cell walls are made up of chitin (polysaccharide). Over 100,000 fungal species identified. Only about 100 are human or animal pathogens. – Most human fungal infections are nosocomial and/or occur in immunocompromised individuals (opportunistic infections). 7 11/23/2012 Dr.T.V.Rao MD
  8. 8. Understanding the Structure of Fungi• Yeasts and molds have different structural and reproductive characteristics – Yeast are unicellular, nucleated rounded fungi while molds are multicellular, filamentous fungi – Yeast reproduce by a process called budding while molds produce spores to reproduce – Some yeast are opportunistic pathogens in that they cause disease in immuno-compromised individuals – Yeast are used in the preparation in the variety of foods 11/23/2012 Dr.T.V.Rao MD 8
  9. 9. Predisposing factors• Use of Antibiotics,• Use of steroids,• Immunosuppressive conditions11/23/2012 Dr.T.V.Rao MD 9
  10. 10. Fungal Diseases • Mycosis- fungal infection – < 100 cause human disease – Not highly contagious – Humans acquire from nature • Groups based on degree on tissue involvement and mode of entry • Cutaneous mycoses-dermatophytes – Epidermis, hair & nails – Contagious-direct or indirect contact – Secrete keratinase that degrades keratin11/23/2012 Dr.T.V.Rao MD 10
  11. 11. Fungal Morphology Hyphae (threads) Yeasts making up a myceliumMany pathogenic fungiare dimorphic, forminghyphae at ambienttemperatures but yeastsat body temperature. 11/23/2012 Dr.T.V.Rao MD 11
  12. 12. Structure of Fungi• Vegetative structures involved in catabolism and growth• Thallus- in molds and fleshy fungi – Tubular filaments of cells-hyphae – Septate hyphae - cross walls that divide them into unicellular units • Pores to allow cytoplasm & nuclei to pass – Coenocytic hyphae- no septa, continuous cells with many nuclei 11/23/2012 Dr.T.V.Rao MD 12
  13. 13. Basic structure of Fungus• Cell wall is rigid• Contains Chitin,Mannan, Polysaccharides,Cytoplasm contains Sterols.Contains True Nuclei, Paired chromosome.Divide Sexually, Asexually or by BothCan have specialized cells11/23/2012 Dr.T.V.Rao MD 13
  14. 14. Characteristics of fungi A. eukaryotic, non- vascular organisms B. reproduce by means of spores, usually wind-disseminated C. both sexual (meiotic) and asexual (mitotic) spores may be produced, depending on the species and conditions D. typically not motile, although a few (e.g. Chytrids) have a motile phase. E. like plants, fungi have an alternation of generations11/23/2012 Dr.T.V.Rao MD 14
  15. 15. Understanding the Terms in Mycology• Simplest Unicellular, Budding yeasts,• Tubular elongations Thread like structures called as Hyphae• Tangled mass is called as Mycelium• Molding produces filamentous fungi.• Septate Aseptate• Grown up Aerial Mycelium• Grows into media Vegetative mycelium11/23/2012 Dr.T.V.Rao MD 15
  16. 16. Understanding the Structure of Fungus• Simplest fungus :- Unicellular budding yeast• Hypha :- Elongation of apical cell produces a tubular, thread like structure called hypha• Mycelium :- Tangled mass of hyphae is called mycelium. Fungi producing mycelia are called molds or filamentous fungi.• Hyphae may be septate or non-septate 11/23/2012 Dr.T.V.Rao MD 16
  17. 17. 11/23/2012 Dr.T.V.Rao MD 17
  18. 18. CLASSIFICATION• Depending on cell morphology 1. Yeasts 2. Yeast like fungi 3. Molds 4. Dimorphic fungi 11/23/2012 Dr.T.V.Rao MD 18
  19. 19. Yeasts • Unicellular fungi which reproduce by budding • On culture - produce smooth, creamy colonies e. g Cryptococcus neoformans (capsulated yeast)11/23/2012 Dr.T.V.Rao MD 19
  20. 20. Yeast like fungi • Grow partly as yeasts and partly as elongated cells resembling hyphae which are called pseudo hyphae. e.g. Candida albicans11/23/2012 Dr.T.V.Rao MD 20
  21. 21. Molds/ Filamentous fungi• Form true mycelia & reproduce by formation of different types of spores.• Vegetative/ aerial hyphae e.g. Rhizopus, Mucor 11/23/2012 Dr.T.V.Rao MD 21
  22. 22. 4. Dimorphic fungi• Occur in 2 forms Molds (Filaments) – 25 C (soil) Yeasts – 37 C (in host tissue) Most fungi causing systemic infections are dimorphic: – Histoplasma capsulatum – Blastomyces dermatidis – Paracoccidioides brasiliensis – Coccidioides immitis – Penicillium marneffei – Sporothrix schenkii 11/23/2012 Dr.T.V.Rao MD 22
  23. 23. Reproduction in fungi• Sexual - formation of Zygospore, ascospores or basidiospores• Asexual reproduction – budding or fission• Asexual spores are formed on or in specialized structures.• Vary in size, shape & colour but these characteristics are constant for a particular species.11/23/2012 Dr.T.V.Rao MD 23
  24. 24. Reproduction in fungi • Micro conidia - Small, single celled • Macro conidia – Large, single or many celled11/23/2012 Dr.T.V.Rao MD 24
  25. 25. Systematic classification• Based on sexual spore formation: 4 classes 1. Zygomycetes 2. Ascomycetes reproduce sexually 3. Basidiomycetes 4. Deuteromycetes (fungi imperfectii)11/23/2012 Dr.T.V.Rao MD 25
  26. 26. Zygomycetes• Lower fungi• Broad, nonseptate hyphae• Asexual spores - Sporangiospores: present within a swollen sac- like structure called Sporangium11/23/2012 Dr.T.V.Rao MD 26
  27. 27. Zygomycetes• Sexual spores - Zygospore: a resting, thick walled cell in between hyphae e.g. Rhizopus, Mucor11/23/2012 Dr.T.V.Rao MD 27
  28. 28. Ascomycetes• Includes both yeasts & filamentous fungi• Narrow, septate hyphae• Asexual spores are called conidia borne on conidiophore 11/23/2012 Dr.T.V.Rao MD 28
  29. 29. Ascomycetes• Sexual spores called ascospores are present within a sac like structure called Ascus.• Several asci may be seen within a fruiting body as seen in Penicillium, Aspergillus• Each ascus has 4 to 8 ascospores.11/23/2012 Dr.T.V.Rao MD 29
  30. 30. Basidiomycetes• Sexual fusion results in the formation of a club shaped organ called base or basidium which bear spores called basidiospores 11/23/2012 Dr.T.V.Rao MD 30
  31. 31. Deuteromycetes or Fungi imperfectii • Group of fungi whose sexual phases are not identified. • Grow as molds as well as yeasts. • Asexual stage – conidia e.g. Candida, Cryptococcus11/23/2012 Dr.T.V.Rao MD 31
  32. 32. Vegetative Structures of Fungi• Arthrospores – formed by segmentation & condensation of hyphae• Chlamydospores – thick walled resting spores e.g. C.albicans11/23/2012 Dr.T.V.Rao MD 32
  33. 33. Asexual Spores• Produced by aerial hyphae: adapted for dispersal• Progeny genetically identical to parent• Several types – Conidiospores- not enclosed in a sac • produced in a chain at end of a conidiophore • Several types – Sporangiospores • Within a sac, sporangium • End of sporangiophore
  34. 34. Sexual Spores• Three phases of development – Plasmogamy-haploid nucleus of a donor cell (+) penetrates the cytoplasm of a recipient cell (-) – Karyogamy- the 2 nuclei fuse to form a diploid nucleus – Meiosis-diploid nucleus gives rise to haploid nuclei – Sexual spores, some + , some -,some recombinants – Sexual spores used to classify fungi into divisions
  35. 35. Fungal Infections/ Mycoses • Superficial mycoses: – 2 types: surface and cutaneous mycoses – Skin, hair & nails. – Mild but chronic disease • Deep mycoses: – 2 types: subcutaneous & systemic mycoses – Caused by soil saprophytes – Infection is accidental – Range from a symptomatic infection to fatal disease11/23/2012 Dr.T.V.Rao MD 35
  36. 36. Superficial: Surface mycoses• Live exclusively on dead surfaces of skin and its appendages• No contact with living tissue, hence no inflammatory response 1. Tinea versicolor 2. Tinea nigra 3. Piedra11/23/2012 Dr.T.V.Rao MD 36
  37. 37. Superficial: Cutaneous mycoses • Cornified layer of skin & its appendages • Contact with living tissue, hence inflammatory & allergic responses seen 1. Dermatophytes – skin, hair & nails 2. 3 genera - Trichophyton Microsporum Epidermophyton11/23/2012 Dr.T.V.Rao MD 37
  38. 38. CHARACTERISTICS OF FUNGI (Continued) Dimorphic Fungi Can exist as both multicellular fungi (molds) and yeasts. Many pathogenic species. – Mold form produces aerial and vegetative hyphae. – Yeast form reproduces by budding. Dimorphism in pathogenic fungi typically depends on temperature: – At 37oC: Yeast form. – At 25oC: Mold form. Dimorphism in nonpathogenic fungi may depend on other factors: Carbon dioxide concentration. 11/23/2012 Dr.T.V.Rao MD 38
  39. 39. Mycoses • Superficial • Cutaneous • Subcutaneous •Systemic • Opportunistic11/23/2012 Dr.T.V.Rao MD 39
  40. 40. Deep mycoses Subcutaneous mycoses Systemic mycoses 1. Mycotic 1. Cryptococcoses Mycetoma 2. Blastomycosis 2. Chromoblastomyc 3. Coccidioidomyc oses oses 3. Sporotrichosis 4. Histoplasmoses 4. Rhinosporidiosis11/23/2012 Dr.T.V.Rao MD 40
  41. 41. Candidiasis• Caused by candida sps, forms a bridge between superficial & deep mycoses as it can cause cutaneous as well as systemic infections• Can also cause opportunistc infections11/23/2012 Dr.T.V.Rao MD 41
  42. 42. Opportunistic infections • Pts with debilitating disease, altered physiological state • Mainly caused by fungi which are common lab contaminant on culture media – Aspergillus – Pencillium – Mucor – Rhizopus • Produce serious & fatal infections11/23/2012 Dr.T.V.Rao MD 42
  43. 43. Useful Properties of Fungi Source of food Antibiotic production e.g. mushrooms e.g. Penicillin from Penicillium notatum Fermentation - Production of alcohol, bread, cheese e.g. Sacchromyces spps11/23/2012 Dr.T.V.Rao MD 43
  44. 44. Useful Properties of Fungi Ergot from Claviceps Vaccines for Hepatitis B – purpurea, used to induce Sacchromyces cerevisiae uterine contractions11/23/2012 Dr.T.V.Rao MD 44
  45. 45. Diagnosis/Treatment• Grown in medium that selects for fungal growth – Grow at 25 C and 37 C• KOH preparations of skin biopsies – Dissolves keratin in skin scrapings or biopsies – Leaves only fungal cells• Therapy- amphotericin B or ketoconazole – Toxic to humans11/23/2012 Dr.T.V.Rao MD 45
  46. 46. • Programme Created by Dr.T.V.Rao MD for Medical and Paramedical Students in the Developing World • Email • doctortvrao@gmail.com11/23/2012 Dr.T.V.Rao MD 46

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