Mycology and Antifungals Flashcards
what are the general structures of mould and their classification. (6)
Sporangium - enclosed unit where spores are found.
Spores - reproduction structures.
Sporangiphore - hypha as stalk of sporangium.
Hyphae - filamentous structure formed together as a network called mycelium.
Rhiziod - ‘roots’ to absorb nutrients.
Mould → multicellular
what are the general structures of yeast and their classification. (7)
Cytoplasm
Ribosome
Mitochondrion
Nucleus
Cell wall
Cell membrane
Yeast → unicellular
what is an example of a superficial fungal disease (3)
- pityriasis versicolor
- hyper/hypo-pigmented lesions with brownish-red scales
- trunk, neck, arms and face
what are common dermatophyte cases (3)
- Tinea cruris (groin infection)
- Tinea pedis (athlete’s foot)
- Tinea unguium (nail bed, discolouration and thickening) - hard to treat as medicine has to penetrate the nail. Treatment normally lasts weeks - months.
why is cryptococcosis C. neoformans dangerous and what is it treated with (5)
- mould within the soil
- yeast within the human host.
- polysaccharide capsule inhibits phagocytosis
- affects the lung, brain and meninges.
- treated with amphotericin B and 5-fluorocytosine combination.
what are the cellular targets of fungal cell walls and how is this achieved (4)
- Glucans
- Mannans
- Chitans
achieved by administering polyoxins.
what is the cellular target of fungal cell membrane, and how is this achieved
Ergosterol is the cellular target of the CELL MEMBRANE
this can be achieved by administering polyenes.
what is the cellular target of fungal nucleus and how is this achieved (3)
- Nucleic acid and DNA and RNA synthesis
- 5-fluorocytosine inhibits the synthesis of nucleic acid synthesis of DNA and RNA.
- griseofulvin stops the fungi from multiplying by affecting microtubule formation.
what is the cellular target of fungal cytoplasm and how is this achieved
squalene
Azoles and Allylamines work by inhibiting squalene.
What are the differences in fungal eukaryotic and animal eukaryotic cells. (4)
- fungal cell wall is 80-90% polysaccharides made up of glucans, mannans and chitins.
- Mannan linkages & side chains give antigen specificity and aid classification.
- Membrane contains lipids & proteins, traces of nucleotides, carbohydrates glucan and mannan.
- Contains the sterol ergosterol in fungi, which is mechanically stronger than cholesterol, which is present in animal cells.
What are the cellular targets of fungal cells (4)
- DNA, RNA & nucleic acid synthesis - nucleus
- Ergosterol - Cell membrane
- Glucans, mannans, chitons - Cell wall
- Squalene - cytoplasm
what are the barriers to fungal infections (7)
- intact skin
- fatty acid content
- epithelial turnover
- humoural factors (e.g. transferrin)
- mucosal surfaces
- pH
- mucosal & ciliary action of the RT
What are the types of fungal infections (4)
- superficial mycoses - epidermis
- cutaneous mycoses - epidermis to dermis
- subcutaneous mycoses - dermis to subcutaneous tissue
- systemic mycoses - bloodstream
what are superficial mycoses (2)
- infection of the skin/hair shaft - no infected living tissue, no cellular response
- e.g. pityriasis versicolor
what are cutaneous mycoses (3)
- infection of skin, hair and nails
- no living tissue is involved, however, pathological changes occur due to infectious agents and their metabolic products
- dermatophytes are common skin plants which utilise keratin
what are subcutaneous mycoses (2)
- rare chronic localised infections of the skin and subcutaneous tissue
- fungi can adapt to the tissue environment usually following trauma
what are dimorphic mycoses (2)
- fungi that change morphological form to overcome the defences of the normal human host
- e.g. histoplama capsulatum - inhaled as mould, turns into yeast cell
what are opportunistic systemic mycoses (2)
- when fungi wait until the defensive mechanism is impaired
- e.g. candida, cryptococcus & aspergillosis
what are candidias (3)
- dimorphic
- affects skin, mucous membranes and nails
- treated with fluconazole and miconazole
how is ergosterol synthesised (3)
- squalene > squalene-2/-3 epoxide
- squalene-2/-3 epoxide > lansosterol
- lansosterol > ergosterol
what is terbinafine (2)
- allylamine
- used for dermatophytes
what is imidazole (2)
- azole
- systemic fungi & dermatophytes
what is itraconazole (2)
- azole
- histoplasmosis & aspergillosis
what is voriconazole
triazole
what is amphotericin
polyene
what is nystatin (2)
- polyene
- systemic candida & dermatophytes
what is griseofulvin used for
dermatophytosis
what is 5-flucytosine (2)
- antimetabolite
- systemic candida & cryptococcus
what is caspofungin used for
aspergillosis
