Introduction_to_Medical_Mycology.pdf

Dr. Özge YILMAZLI Medical Microbiology Department  The branch of science which investigating yeasts, molds and macrofungi is called mycology.  They are common in nature (in air, water, decomposing organic material).  There are about 400,000 different types of fungi on earth.  Only about...

Dr. Özge YILMAZLI Medical Microbiology Department  The branch of science which investigating yeasts, molds and macrofungi is called mycology.  They are common in nature (in air, water, decomposing organic material).  There are about 400,000 different types of fungi on earth.  Only about 200 of them cause disease in animals and humans.  10-20 species of fungi responsible 90% of all fungal infections. Fungi are non-photosynthetic eukaryotic organisms that do not contain chlorophyll They are eukaryotic organisms that are distinguished from other eukaryotes by a rigid cell wall composed of chitin and glucan and this cell wall is different from the bacteria’s cell wall A cell membrane which has ergosterol as the major sterol component -taking place cholesterol in human cells-  Decomposition of animal and vegetable wastes  Obtaining some vitamins  Thiamin (B1)  Obtaining some cheese types (Roquefort (Penicillium roquefort), Camembert (Penicillium camemberti))  Biotin (B7)  Obtaining antibiotics (penicillin,  Amylas (Starch), Pectinase cephalosporin)  Riboflavin (B2)  Obtaining some enzymes Pectin)  Obtaining hormones  Gibberellin (In plants)  Obtaining fermented products such as bread, wine and beer  Various diseases in humans, animals and plants  Spoilage of food and foodstuffs  They can even develop in the gas tanks of planes and cause to crash. MAIN STRUCTURE OF CELLS Like animal cells, fungi also eukaryotic cells, 1. Nucleus  Nucleus membrane  Nucleolus  2. Cytoplasm  Endoplasmic reticulum  Golgi apparatus  Mitochondria  Vacuoles  80S Ribosomes  3. Cell membrane  4. Cell wall  5. Capsule  Structure: polysaccharide  Functions: prevent phagocytosis/antiphagocytic effect  Virulence factor  Cryptococcus neoformans  It is antigenic structure of fungi  Cell Wall Components  Structure: multilayer  Chitin: N-acetyl glucosamines  Polysaccharides (~90%): chitin, cellulose, glucan, mannan polymers  The type and amount of polysaccharide varies from species to species  Proteins and glycoproteins (~10%)  Functions: gives shape, protects from osmotic shock (NAGA)  Mannan: is a mannose polymer  Glucan: consists of D-glucose monomers linked by glycoside bonds  Cellulose: 𝛽-glucose derivative, also called 𝛽-1,4-glucan  Structure :phospholipid  Sterols (ergosterol, zymosterol)  Since it is similar to the cytoplasm membrane of human cells, most of the drugs used in the treatment of fungal infections also have a toxic effect on the human cell.  Antifungal drugs have been developed that target ergosterol and zymosterol, which are not found in the human cell membrane. These can be effective against fungi without harming human cells.  Protects the cytoplasm  Regulates intracellular uptake and secretion  Regulates capsule and cell wall synthesis 1. Yeasts and yeast-like fungi Uni-cellular Reproduces by budding 2. Molds Multi-cellular Exhibit hyphae structure 3. Dimorphics Mold at room temperature, yeast at body temperature  Reproduces by budding or division  A protrusion forms from the parent cell and this grows to form the daughter cell (blastoconidium)  The daughter cell can elongate without leaving from the parent cell and form sausage-like pseudohyphae  Yeasts are in unicellular form, smooth and creamy colonies on agar  Composed of tubular structures called hyphae  Rope-like and multicellular  Hyphae are elongated by apical elongation  Hyphae can be with or without septum  Colonies formed by molds; referred to as filamentous, hairy or woolly  The hyphae come together to form a complex structure called mycelium  Vegetative hyphae extending to the bottom of the culture medium when molds grow on agar  Forms aerial hyphae extending out of the medium  Some aerial hyphae contain spores (conidia) that allow fungi to reproduce  These are called reproductive micelles  Some fungi exhibit thermal dimorphism  It can be found in the form of yeast or mold depending on environmental conditions.  Yeast form at 37°C and in-vivo conditions  Mold form in natural environment and room temperature (infectious form)  Yeasts and molds cause disease mostly in immunedeficient individuals  Especially being HIV (+), receiving chemotherapy or having an underlying disease is an important risk factor  Opportunistic pathogen  Dimorphic fungi are absolute pathogens.  They are also capable of causing disease in healthy individuals.  Absolute pathogen  1. Zygospore:  Two hypha getting closer  A cell with rich cytoplasm is formed at each end  The septum between two girl cell dissappears  A thick-walled zygospore is formed  3. Basidiospore:  2. Ascospore:  Spores formed in the ascus  Each askus has 2-8 spores  It is found in structures called sterigmata at the ends of the knobshaped formations called basidium  2. Chlamydospore:  The walls of some cells in hyphae  1. Blastospor:  Spore formed as a result of budding from different parts of yeast cells  Spores are released when matured  Sometimes spores form pseudohyphae without leaving the parent cell.  Candida species or pseudohyphae gets thick  It becomes more resistant to environmental conditions  Candida albicans, C. dubliniensis  Used to distinguish C. albicans and C. dubliniensis from other Candida species  3. Arthrospore:  Occurs only in mold form  4. Conidiospore:  Occurs as a result of separation of  Unicellular ones microconidia hyphae by transverse septa  Mold form of Coccidioides immitis  Aspergillus spp.  The multicellular ones are the macroconidia  Microsporum spp.  5. Sporangiospore:  Spores are found in large and round sacs (sporangium) formed at the ends of special hyphae (sporangiophores) that carry them  The lower part of the sporamgium contains the supporting columella  With the bursting of the sporangium, the spores spread and develop under suitable conditions  Penicillium spp.  Superficial Mycoses  Limited to the very superficial surfaces of the skin and hair.  They are non-destructive, cosmetic importance only.  Pityriasis versicolor (Malassezia furfur) is characterized by hyper/hypopigmentation of the skin.  Black piedra (Piedraia hortae) is black and hard to remove macular patches seen only at the ends of the hair.  White piedra (Trichosporon beigelii) is characterized by yellowish macular patches at the ends of the hair.  Subcutaneous Mycoses:  Subcutaneous mycoses involve the deeper layers of the skin, including the cornea, muscle, and connective tissue, and are caused by a broad spectrum of taxonomically diverse fungi  The fungi access to the deeper tissues usually by traumatic inoculation and remain localized, causing abscess formation, non-healing ulcers, and draining sinus tracts  Endemic Mycoses  Opportunistic Mycoses  Histoplasma capsulatum  Cryptococcus neoformans  Coccidioides immitis  Encapsulated yeast can  Blastomyces dermatitidis  Paracoccidoides brasiliensis reproduce at 37°C, is found in pigeon feces and shows CNS spread These fungi exhibit thermal dimorphism (exist as yeasts or spherules at 37°C and molds at 25°C)  Candida sp Endemic in some ecological niches  Class of Zygomycetes (Rhizopus,  Aspergillus sp  Pneumocystis carinii Mucor, Rhizomucor, Absidia) 1. Soil and natural habitat 2. Inhalation of spores Transmission Routes 3. Inoculation from the skin 4. From normal flora (opportunistic pathogen) 5. Human-to-human transmission  3. Culture:  Sabouraud dextrose agar (SDA)  ChromCandida agar  1. Microscopy:  4. Serological Methods:  10% potassium hydroxide for  Latex agglutination for cryptococcal keratinized tissues,  Gram stain yeast and pseudohyphae  Encapsulated yeast with Indian ink  Calcoflor White dye  2. Molecular Methods (PCR) antigen in blood or CSF  Galactomannan test for Invasive Aspergillosis