Introduction To Medical Mycology PDF

INTRODUCTION TO MEDICAL MYCOLOGY Mycology - - Myco (fungi), logy (study) Mycologists --scientists who study fungi. Mycology --scientific discipline dealing with fungi. Mycoses --diseases caused in animals by fungi. Mykos = mycete = fungus General characteristic A fungus is any member of the...

INTRODUCTION TO MEDICAL MYCOLOGY Mycology - - Myco (fungi), logy (study) Mycologists --scientists who study fungi. Mycology --scientific discipline dealing with fungi. Mycoses --diseases caused in animals by fungi. Mykos = mycete = fungus General characteristic A fungus is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds. These organisms are classified as a kingdom. Most are multicellular, but yeasts are unicellular. Most are aerobes or facultative anaerobes. Growth is their means of mobility. Both sexual and asexual spore may be produced. A characteristic that places fungi in a different kingdom from plants and bacteria is chitin in their cell walls. Fungi are heterotrophic organisms, similar to animals lack of chlorophyll, (plant; autotrophic). Many are ecologically important saprophytes (consume dead and decaying matter) Others are parasites. Store their food as glycogen (plant; starch) Over 100,000 fungal species identified. Only about 100 are human or animal pathogens. Most human fungal infections are nosocomial. The fungal characteristics that use in Classification: Cell wall (the cell wall chemical component), Somatic phase, Reproduction, Nutrition, The structural that formed by fungi, Fruiting bodies, Spores. Depending on Morphology 1. Yeasts 2. Yeast like fungi 3. Molds 4. Dimorphic fungi, mold phase & yeast phase Classified by method of sexual reproduction 1. Zygomycetes (common bread mold—Rhizopus) 2. Basidiomycetes (puffballs & common mushrooms) 3. Ascomycetes (Dutch elm disease/rye smut) 4. Deuteromycetes (fungi imperfection) First three groups is based on their method of sexual reproduction. 4th group, the Deuteromycetes, have NO sexual reproduction. SEXUAL SPORE CLASS Zygospore-------------Zygomycetes Basidiospore----------Basidiomycetes Ascospore-------------Ascomycetes None/Unknown------Deuteromycetes, Fungi Imperfecti. Asexual Spores Conidiospores Chlamydospores Sporangiospores Blastospores Arthrospore YEAST Non-filamentous, unicellular fungi Oval to round, Pasty colonies (resemble bacteria) Facultative Anaerobes, Fermentation produce: ethanol and CO2. Reproduction FISSION, even, reproduction, nucleus divides forming two identical cells, like bacteria. BUDDING, uneven, reproduction, parent cell’s nucleus divides and migrates to form a bud and then breaks away. Fungal Structure Thallus - body Molds & fleshy fungi have these structures Long filaments of cells (hyphae): » Septate hyphae (cross wall): most fungi » Aseptate hyphae (coenocytic ): no cross wall, continous mass with many nuclei. Mycelium Abundance growth of aerial hyphae resulting a mass can be observed with eyes. Vegetative Hypha Composed of cells involved in catabolism and growth. Reproductive Hypha (aerial) Composed of cells involved in reproduction (produce spores). MYCOSES Superficial ( skin, hair, cornea) Cutaneous ( Dermatophytosis ) Subcutaneous Systemic (deep) (endemic) Superficial mycoses (or tineas) mostly occur in the tropics and are restricted to the outer surface of the hair and skin. examples are: Piedraia hortae, a filamentous member of the Ascomycota which causes black piedra, a disease of the hair shaft characterized by brown/black nodules on the scalp hair. Cutaneous mycoses there are three genera of fungi that commonly cause disease in the non-living tissues of skin, hair, or nails/claws of people and animals, by growing in a zone just above where the protein keratin is deposited. These three genera are Microsporum, Trichophyton and Epidermophyton (all filamentous Ascomycota) and they are often labelled dermatophytes (with the disease being called dermatophytosis). Subcutaneous mycoses are generally caused by fungi that are normally saprotrophic inhabitants of soil, which become infective by being introduced through wounds in the skin. Most infections involve people who normally walk barefoot. Madurella mycetomatis and M. grisea (filamentous, Ascomycota) cause human mycetoma (common name: madura foot). Systemic mycoses are infections that affect the whole body. We divide these into mycoses due to primary (usually dimorphic) virulent pathogens, and those due to opportunistic pathogens.