Medical Mycology (MLSM 507) Introduction PDF

MEDICAL MYCOLOGY (MLSM 507) IMPORTANT TERMINOLOGIES Mycology The branch of science focused on the study of fungi, including their genetics, taxonomy, and pathogenicity in humans and other organisms. Medical Mycology Medical Mycology is the branch of science that...

MEDICAL MYCOLOGY (MLSM 507) IMPORTANT TERMINOLOGIES Mycology The branch of science focused on the study of fungi, including their genetics, taxonomy, and pathogenicity in humans and other organisms. Medical Mycology Medical Mycology is the branch of science that studies fungi capable of causing disease in humans and other animals. It focuses on understanding the biology, taxonomy, and pathology of fungal organisms that lead to infections. These infections, known as mycoses, can range from superficial skin conditions (such as athlete’s foot) to life-threatening systemic diseases (such as cryptococcosis or invasive candidiasis), particularly in immunocompromised individuals. Fungi These are eukaryotic, heterotrophic, unicellular (e.g yeasts and molds) to multicellular (e.g mushrooms), rigid cell walled, spore bearing, non-vascular microorganisms which differ from plants, animals and bacteria. They are ubiquitous in nature and usually reproduce by both sexual and asexual means. Many of which cause infections in humans. Mycotoxin Mycotoxins are toxic compounds produced by certain fungi, typically molds, that can contaminate food, feed, or air. These toxins pose a significant health risk to humans and animals when ingested, inhaled, or absorbed through the skin. Examples include aflatoxins and ochratoxins. Mycotoxicosis Mycotoxicosis refers to poisoning or toxic illness caused by exposure to mycotoxins. Unlike infections caused by fungi, mycotoxicosis results from ingesting or inhaling fungal toxins, often through contaminated food. Symptoms vary depending on the toxin and exposure level, and the condition can lead to serious health issues, including liver damage, immunosuppression, and even cancer. Fungaemia Fungaemia is the presence of fungi or yeast in the bloodstream, typically resulting from invasive fungal infections. It is a serious condition that can lead to sepsis or disseminated fungal infections, especially in immunocompromised individuals. Common fungi causing fungaemia include Candida species and Aspergillus. Hyphae The long, thread-like structures that form the mycelium of fungi. Hyphae can be septate (divided by cross- walls) or non-septate (coenocytic). 1 Mycelium A mass of hyphae that forms the vegetative part of a fungus, from which it absorbs nutrients and grows. Conidia Asexual spores formed by fungi that are dispersed to propagate the organism. Conidia are important in the spread of fungal infections and identification of fungi. Yeasts Unicellular, round or oval-shaped fungi that reproduce mainly by budding. Examples include Candida species which can cause infections in humans. Molds Multicellular fungi that grow in filamentous form with hyphae. Molds like Aspergillus can be pathogenic, especially in immunocompromised individuals. Dimorphic Fungi Fungi that can exist as yeasts or molds, depending on environmental conditions, such as temperature. Pathogenic dimorphic fungi include Histoplasma and Blastomyces. Monomorphic fungi Monomorphic fungi are fungi that exist in a single form (either as a yeast or a mold) throughout their entire lifecycle, regardless of environmental conditions. Unlike dimorphic fungi, which can switch between yeast and mold forms depending on factors such as temperature, monomorphic fungi maintain a consistent morphological state. Sporulation The process by which fungi produce spores for reproduction. In pathogenic fungi, spores are often inhaled and lead to pulmonary infections. Dermatophytes A group of fungi that infect keratinized tissues, including skin, hair, and nails, causing superficial infections like athlete's foot and ringworm. Opportunistic Mycoses Infections caused by fungi that usually do not cause disease in healthy individuals but can become pathogenic in immunocompromised people, such as Candida and Aspergillus. Systemic Mycoses Fungal infections that affect internal organs or the entire body. These infections are often caused by inhalation of fungal spores and can be life-threatening. Examples include Histoplasmosis and Coccidioidomycosis. 2 Histoplasmosis A systemic mycosis caused by Histoplasma capsulatum, a dimorphic fungus found in soil contaminated with bird or bat droppings. It can lead to respiratory illness. Candidiasis An infection caused by Candida species, especially Candida albicans. It can cause superficial infections like thrush or serious systemic infections, especially in immunocompromised patients. Aspergillosis A spectrum of diseases caused by species of the genus Aspergillus. It commonly affects the lungs and can lead to invasive infections in immunocompromised individuals. Antifungal Resistance The ability of fungi to survive and proliferate despite the presence of antifungal agents. This has become an increasing concern in the treatment of fungal infections, particularly in strains of Candida and Aspergillus. Ergosterol A key component of fungal cell membranes, analogous to cholesterol in animal cells. Many antifungal drugs, such as azoles and polyenes, target ergosterol to disrupt fungal cell function. Azole Antifungals A class of antifungal drugs that inhibit the synthesis of ergosterol, disrupting the fungal cell membrane. Examples include fluconazole and itraconazole. Polyene Antifungals A group of antifungal drugs that bind to ergosterol and create pores in the fungal cell membrane, leading to cell death. Amphotericin B is a well-known polyene used to treat severe systemic mycoses. Saprobes Fungi that live on dead or decaying organic matter, obtaining nutrients through decomposition. Some saprobes can be opportunistic pathogens in humans, especially in immunocompromised individuals. Chitin Chitin is a long-chain polymer made of N-acetylglucosamine, a derivative of glucose. It is a key structural component found in the cell walls of fungi, providing rigidity and strength. Chitin is similar in function to cellulose in plants and serves to protect the fungal cell, maintaining its shape and integrity. It is also found in the exoskeletons of arthropods (like insects and crustaceans). Chitin is significant because it forms part of the fungal cell wall, a target for certain antifungal drugs that aim to disrupt the cell wall's integrity and prevent fungal growth. 3 Zygospore A zygospore is a thick-walled, resistant spore formed by the fusion of two specialized cells (gametangia) from different mating types in fungi belonging to the Zygomycota phylum. This spore is produced sexually and can withstand harsh environmental conditions. Upon favorable conditions, the zygospore germinates, leading to the formation of new fungal structures. Zygospores are characteristic of fungi like Rhizopus (black bread mold). Basidiospore A basidiospore is a reproductive spore produced by Basidiomycota, a class of fungi that includes mushrooms, rusts, and smuts. Basidiospores are formed on specialized club-shaped structures called basidia during sexual reproduction. They are typically dispersed by wind or other mechanisms and are key to the fungal life cycle, leading to the formation of new fungal organisms when they germinate. Ascospore An ascospore is a sexually produced spore formed within a sac-like structure called an ascus in fungi of the phylum Ascomycota. Ascospores are usually produced in groups of eight within each ascus, and they play an essential role in the reproductive cycle of fungi such as yeasts (Saccharomyces) and molds (Aspergillus and Penicillium). Sporangiospore A sporangiospore is an asexual spore produced inside a structure called a sporangium. These spores are characteristic of certain fungi, especially those in the Zygomycota phylum. When the sporangium ruptures, sporangiospores are released into the environment and can germinate to form new fungal colonies. Sporangium A sporangium is a specialized, often sac-like structure in fungi where asexual spores (sporangiospores) are produced and stored. Once mature, the sporangium ruptures or releases its spores, which can disperse to new environments and germinate. Fungi like Rhizopus produce sporangia. Sporangiophore A sporangiophore is the specialized hyphal structure or stalk that supports the sporangium. It elevates the sporangium to aid in the dispersion of the sporangiospores. This structure is often seen in fungi that reproduce via sporangiospores. Blastospore A blastospore (or blastoconidium) is an asexual spore formed by budding from a parent fungal cell, typically found in yeasts such as Candida or Cryptococcus. It is a form of vegetative reproduction and can lead to the formation of a new yeast cell. 4 Thallospore A thallospore is a type of asexual spore formed from the thallus (body) of a fungus. This term can include arthrospores (spores formed by fragmentation of hyphae) and chlamydospores (thick-walled spores formed under harsh conditions). Thallospores are produced through vegetative reproduction. Budding Budding is a type of asexual reproduction in fungi, particularly yeasts, where a new daughter cell forms as a small outgrowth (bud) from the parent cell. Once the bud matures, it separates and becomes an independent organism. Budding is a common reproductive mechanism in yeasts like Saccharomyces cerevisiae and Candida species. 5