Introduction To Mycology
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Introduction
Mykos: Fungus.
Mycoses: A disease caused by a fungus.
о Fungi are eukaryotic organisms. о Cell wall contains chitin. о Cell membrane contains ergosterol.
Introduction о Most fungi are obligate aerobe, some are facultative anaerobe, but none are anaerobe. о Some fungi reproduce by forming sexual spore & some asexually by forming conidia.
Several Terms о Yeast: Unicellular, oval to round reproduce by asexual budding. о Mold: Long filaments, multicellular (hyphae). May be septate or nonseptate.
Yeast
Structure of a Mushroom
Terminology
Pseudohyphae – “Hyphae” formed by “budding” yeasts when the buds do not separate from the mother cell.
Mycelium – A term describing the “network” of hyphae.
Terminology
Dimorphism: Capable of growing in mold or yeast form under different environmental conditions.
Several medically important fungi are thermally dimorphic; Molds in environment & yeast in human.
Reproduction of fungus Asexual: Spores: Arthrospore, Chlamydospore, Blastospore, Sporangiospore. Budding (yeast): New cell grows on mature cell then breaks off. Sexual: Mating: Hyphae of 2 fungi grow together and exchange genetic material. Spores: Zygospore, Ascospore, Basidiospore.
Importance of fungi
Harmful:
Diseases in plants and animals, Toxins.
Useful:
Primarily decomposers – return organic matter to the soil.
Used to produce antibiotics like penicillin.
Used for food – Pizza, Beer, wine, Bread, mushrooms, yeast.
Risk Factors for Fungal Infections
Trauma to the skin.
Diabetes & immunocompromised (older pts., steroid use, HIV infection).
Poor nutrition.
Restrictive footwear.
Sports participation.
Living in a warm, moist climate.
Fungal Toxin
Fungal toxin includes:
Amanitin & phaloidin – Produced by amanita mushrooms are potent hepatotoxic.
Alkaloids (ergotamine & diethylamide) – Produced by Claviceps purpura causes vascular & neurologic effects.
Aflatoxin – Produced by Aspergillus flavus cause liver damage and hepatic carcinoma.
LABORATORY DIAGNOSIS
Direct microscopic examination: Gram stain, potassium hydroxide (10% KOH), calcofluor white, India ink prperation.
Culture: Sabouraud dextrose agar.
DNA probe.
Serology.
Antifungal drugs
Antifungal drugs includes:
Amphotericin B: Disrupts cell membrane.
Azoles (Fluconazole, ketoconazole, itrakonazole, miconazole etc. inhibits ergosterol synthesis.
Nystatin – Used topically for candida infection.
Mykos: Fungus.
Mycoses: A disease caused by a fungus.
о Fungi are eukaryotic organisms. о Cell wall contains chitin. о Cell membrane contains ergosterol.
Introduction о Most fungi are obligate aerobe, some are facultative anaerobe, but none are anaerobe. о Some fungi reproduce by forming sexual spore & some asexually by forming conidia.
Several Terms о Yeast: Unicellular, oval to round reproduce by asexual budding. о Mold: Long filaments, multicellular (hyphae). May be septate or nonseptate.
Yeast
Structure of a Mushroom
Terminology
Pseudohyphae – “Hyphae” formed by “budding” yeasts when the buds do not separate from the mother cell.
Mycelium – A term describing the “network” of hyphae.
Terminology
Dimorphism: Capable of growing in mold or yeast form under different environmental conditions.
Several medically important fungi are thermally dimorphic; Molds in environment & yeast in human.
Reproduction of fungus Asexual: Spores: Arthrospore, Chlamydospore, Blastospore, Sporangiospore. Budding (yeast): New cell grows on mature cell then breaks off. Sexual: Mating: Hyphae of 2 fungi grow together and exchange genetic material. Spores: Zygospore, Ascospore, Basidiospore.
Importance of fungi
Harmful:
Diseases in plants and animals, Toxins.
Useful:
Primarily decomposers – return organic matter to the soil.
Used to produce antibiotics like penicillin.
Used for food – Pizza, Beer, wine, Bread, mushrooms, yeast.
Risk Factors for Fungal Infections
Trauma to the skin.
Diabetes & immunocompromised (older pts., steroid use, HIV infection).
Poor nutrition.
Restrictive footwear.
Sports participation.
Living in a warm, moist climate.
Fungal Toxin
Fungal toxin includes:
Amanitin & phaloidin – Produced by amanita mushrooms are potent hepatotoxic.
Alkaloids (ergotamine & diethylamide) – Produced by Claviceps purpura causes vascular & neurologic effects.
Aflatoxin – Produced by Aspergillus flavus cause liver damage and hepatic carcinoma.
LABORATORY DIAGNOSIS
Direct microscopic examination: Gram stain, potassium hydroxide (10% KOH), calcofluor white, India ink prperation.
Culture: Sabouraud dextrose agar.
DNA probe.
Serology.
Antifungal drugs
Antifungal drugs includes:
Amphotericin B: Disrupts cell membrane.
Azoles (Fluconazole, ketoconazole, itrakonazole, miconazole etc. inhibits ergosterol synthesis.
Nystatin – Used topically for candida infection.
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