Transcript MYCOLOGY
MYCOLOGY Xiao-Kui Guo PhD Classification Based on molecular evidence: base sequences from ribosomal RNA (Patterson & Sogin 1992) Comparison of fungi and bacteria feature fungi bacteria diameter 4um 1um nucleus Eukaryotic prokaryotic cytoplasm Mitochondria and endoplasmic reticulum present Mitochondria and endoplasmic reticulum present Cell membrane Sterols present Sterols absent Cell wall chitin peptidoglycan spores Sexual and asexual spores for Endospores for survival, reproduction not for reproduction Thermal dimorphism yes No metabolism Require organic carbon; no obligate anaerobes May do not require organic carbon; many obligate anaerobes Medically important fungi Includes 4 phyla Ascomycota（子囊菌门）- Sexual reproduction in a sack called an ascus with the production of ascopspores. Basidiomycota（担子菌门）-Sexual reproduction in a sack called a basidium with the production of basidiospores. Zygomycota（接合菌门） - sexual reproduction by gametes and asexual reproduction with the formation of zygospores. Mitosporic Fungi（Fungi Imperfecti，半知菌门） - no recognizable form of sexual reproduction. Includes most pathogenic fungi. Structure of fungi Morphology Unicellular fungi Multicellular fungi Hypha: mycelium (vegetative, aerial or reproductive). Spores: asexual spore a) Conidium（分生孢子）: macroconidium, microconidium. b) Thallospore（叶状孢子）: blastospore（芽生）, chlamydospore（厚 膜）,arthrospore（关节）. c) Sporangiospore(孢子囊孢子） Uni cel l ul ar f ungi Multicellular fungi Hypha •spore Hypha 大分生孢子 假菌丝 芽生孢子 孢子囊孢子 关节孢子 厚膜孢子 Dimorphism （二相性真菌） Culture Sabouraud culture medium optimal pH 4-6 optimal temperature 22-28 C some deep pathogenic fungi need 37 C, Aerobic types of colonies– yeast, filamentous Multiplication:budding, hypha formation, branching or disruption of hypha, spore formation Resistance Resistant to dry, sunlight, UV light and many chemicals Sensitive to wet heat four types of mycotic diseases: Hypersensitivity - an allergic reaction to molds and spores. Mycotoxicoses - poisoning of man and animals by feeds and food products contaminated by fungi which produce toxins from the grain substrate. Mycotoxin and tumor Mycetismus - the ingestion of toxin (mushroom poisoning). Infection Immunity Nonspecific immunity Specific immunity DIAGNOSIS 1. Skin scrapings suspected to contain dermatophytes or pus from a lesion can be mounted in KOH on a slide and examined directly under the microscope. 2. Skin testing (dermal hypersensitivity) used to be popular as a diagnostic tool. 3. Serology may be helpful when it is applied to a specific fungal disease. 4. Direct fluorescent microscopy. 5. Biopsy and histopathology. 6. Culture. Pathogenic fungi are usually grown on Sabouraud dextrose agar . It has a slightly acidic pH (~5.6); cyclohexamide, penicillin, streptomycin or other inhibitory antibiotics are often added to prevent bacterial contamination and overgrowth.