MYCO

• Mycology is a specialized discipline in the field of biology concerned with the study of fungi
• There are 80,000 species described under mycology/fungi, but only >400 are medically important and >50 can cause 90% of fungal infections in humans and animals
• Fungi are used for both beneficial and harmful activities
• Beneficial activities of fungi include:

  • Food and food production such as cheese, fermentation of alcoholic drinks, beers (yeast), and bread
  • Industrial production of useful bioactive secondary metabolites like antibiotics (penicillin from penicillium) and immunosuppressive drugs (cyclosporin - fungus originated drug)
  • Decomposition, essential in breaking down and recycling organic matter like leaves to return nutrients to the soil
• Harmful activities of fungi include:

  • Destruction of materials
  • Spoilage of stored food
  • Destruction of crops by phytopathogens causing fungal diseases in crops like corn, grains, rice, and other plants
  • Fungal infections termed as Mycosis in skin, tissues, organs, and blood
• Fungi are eukaryotic organisms possessing different cellular organelles like nucleus, nuclear membrane, mitochondria, endoplasmic reticulum, and a secretory apparatus capable of degrading organic substrates into soluble nutrients
• Fungi can be obligate or facultative aerobes, chemotrophic, achlorophyllous, exogenous, and have rigid cell walls with high amounts of carbohydrate layers mainly made up of chitin
• Fungi have virulence factors but unlike bacteria, their infections are generalized and not specific, with clinical manifestations ranging only to 1-2 for specific fungi
• Fungi can reproduce both sexually (teleomorph) and asexually (anamorph)
• Classification of fungi includes forms like yeast (unicellular, reproduce through budding or fission) and mold (multicellular filamentous colonies with hyphae and mycelium)
• Dimorphic fungi can exist as yeast or mold depending on specific temperatures and are the cause of systemic mycoses
• Fungal structures include thallus, hyphae, and different types of hyphae shapes like antler, racquet, spiral, and rhizoid
• Fungal structures can vary in pigmentation with hyaline hyphae being non-pigmented and dematiaceous hyphae being darkly pigmented
• Fungi reproduce through asexual spores (anamorph) like blastopores and chlamydospores
• Asexual spores include Blastopores/Blastocomidia, Chlamydospore, Sporangiospore, Conidiospore, and Arthrospore
• Blastopores/Blastocomidia reproduce through budding from parent cell
• Chlamydospore is a thick-walled spore formed by rounding and enlargement within a hyphal segment, examples include Candida albicans
• Sporangiospore has a sac that is enclosed and a columella which holds the spores, examples include Rhizopus spp.
• Conidiospore is without a sac and is not enclosed, examples include Penicillium
• Arthrospore is barrel-shaped spores formed by fragmentation from hyphal segments, usually occurs in Septate hyphae, examples include Trichosporon spp., Coccidioides spp., and Geotrichum spp.
• Sexual spores are formed through plasmogamy and mating through compatible strains
• Zygospore is large spores enclosed in a thick wall, the sexual form is Zygomycota
• Ascospores are found in the sexual form Ascomycota, each ascus has 4-8 ascospores inside
• Basidiospores usually have 4 basidiospores in each basidium
• Laboratory diagnosis includes specimen collection, direct microscopic examination, culture, mycologic identification, and antifungal agents
• Specimen collection varies based on the site of infection, including superficial, cutaneous, subcutaneous, and systemic
• Direct microscopic examination involves Gram stain, 10% KAH or NaOH, Calcofluor white, India ink method, and Giemsa/Wright stain
• Culture includes primary recovery media and differential test media
• Mycologic identification involves macroscopic examination, microscopic examination using LPCB, and histologic stains like Periodic Acid Shift and Gomori's Methenamine Silver Stain
• Antifungal agents include Polyene antibiotics, Imidazole compounds, Polyoxin compound, and Echinocandins
• Types of light microscopes include Brightfield, Darkfield, Phase Contrast, Ultraviolet, Fluorescence, Inverted, Interference, and Electron microscopes