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Lecture 15 - Cutaneous and Opportunistic Fungal Infections

Lecture 15 - Cutaneous and Opportunistic Fungal Infections...

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Lecture 15 - Cutaneous and Opportunistic Fungal Infections MI-34a. List the differences between yeasts and molds regarding macroscopic and microscopic appearance and mode of replication General Class: Fungi Widely distributed in nature (air, water, soil, decaying organic matter) Break down dead plant tissue About 400,000 species Facultative anaerobe/strict aerobe Non are strict anaerobe Structures: Stalk – mycelia (nutrients) the vegetative part – form by mass of hyphae Spores – are the reproductive units The wind blows the spores and spread them (the daughter will grow up away from the fungus) conidiophores – specialized structure for holding spores conidio - spores Cell Wall (usually very thick cell wall) Glucan - beta (alpha) linked glucose Mannan - alpha linked mannose Chitin - beta linked N-acetylglucosamine Cell wall had multi layer – with different types of carbohydrates Membrane Primary sterol is ergosterol rather than cholesterol The reason for the majority of the antifungal drugs They inhibit the synthesis of ergosterol more than cholesterol This difference is the basis for two classes of anti-fungal drugs Amphotericin B (binds to ergosterol and destablizes the membrane) Imidazoles Mycelia Vegetative Undifferentiated , form early , grow into media to obtain nutrients nutrition Aerial Bear spores , form later , grow up into the air reproduce - ***Spores are like the seeds of plants - a form to allow movement of the organism in the environment Nutrients: fungi grow into their food! Most often live on dead organic matter They secrete enzymes that break down complex carbohydrates and proteins Do NOT photosynthesize Ubiquitous!! Found everywhere Fungi are the most common organisms in the air we breathe We are all exposed to fungi on a daily basis Those who live in a moldy environment are more exposed than others Fungi are not spread person to person Fungi = Eukaryotes 80S ribosomes (they are more like us) Membrane bound organelles Sterols in cytoplasmic membranes Multiple linear chromosomes Sexual orientation and name Most, but not all, fungi have a sexual form Fungi typically look different in the sexual vs the asexual state Mycologists give the sexual state a different name than the asexual state We will use the asexual names in this course Yeasts Molds Microscopic - Sabauraud Agar : Colony --- like bacteria (smooth colonies) - black center clear space around it = capsule - Sabauraud Agar : Colony – fuzzy (mold grows up into the air, WET)
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Macroscropic - Do not have specialized structures - forms spores (conidia ) in environment and culture - require spore formation (sporulation) - Special structure (mycelia, spores) - Mode of replication Budding - Through YMC (yeast mother cell) Ph (pseudohypae – a daughter cell) - Daughter cells significantly smaller than mother - NO SPORES - In tissue, ****Aspergillus hyphae: note there are no spores; only see hyphae
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