Mycology and Antifungals Flashcards

1
Q

what are the general structures of mould and their classification. (6)

A

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

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2
Q

what are the general structures of yeast and their classification. (7)

A

Cytoplasm

Ribosome

Mitochondrion

Nucleus

Cell wall

Cell membrane

Yeast → unicellular

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3
Q

what is an example of a superficial fungal disease

A

pityriasis versicolor

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4
Q

what are common dermatophyte cases (3)

A
  1. Tinea cruris (groin infection)
  2. Tinea pedis (athlete’s foot)
  3. Tinea unguium (nail bed, discolouration and thickening) - hard to treat as medicine has to penetrate the nail. Treatment normally lasts weeks - months.
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5
Q

why is cryptococcosis C. neoformans dangerous and what is it treated with (5)

A
  1. mould within the soil
  2. yeast within the human host.
  3. polysaccharide capsule inhibits phagocytosis
  4. affects the lung, brain and meninges.
  5. treated with amphotericin B and 5-fluorocytosine combination.
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6
Q

what are the cellular targets of fungal cell walls and how is this achieved (4)

A
  1. Glucans
  2. Mannans
  3. Chitans

achieved by administering polyoxins.

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7
Q

what is the cellular target of fungal cell membrane, and how is this achieved

A

Ergosterol is the cellular target of the CELL MEMBRANE

this can be achieved by administering polyenes.

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8
Q

what is the cellular target of fungal nucleus and how is this achieved (3)

A
  1. Nucleic acid and DNA and RNA synthesis
  2. 5-fluorocytosine inhibits the synthesis of nucleic acid synthesis of DNA and RNA.
  3. griseofulvin stops the fungi from multiplying by affecting microtubule formation.
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9
Q

what is the cellular target of fungal cytoplasm and how is this achieved

A

squalene

Azoles and Allylamines work by inhibiting squalene.

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10
Q

What are the differences in fungal eukaryotic and animal eukaryotic cells. (4)

A
  1. fungal cell wall is 80-90% polysaccharides made up of glucans, mannans and chitins.
  2. Mannan linkages & side chains give antigen specificity and aid classification.
  3. Membrane contains lipids & proteins, traces of nucleotides, carbohydrates glucan and mannan.
  4. Contains the sterol ergosterol in fungi, which is mechanically stronger than cholesterol, which is present in animal cells.
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11
Q

What are examples of antifungals (9)

A
  • amphotericin B and 5-fluorocytosine combination → Cryptococcosis C. neoformans
  • Terbinafine (allylamine) → dermatophytes
  • Imidazole → systemic fungi and dermatophytes.
  • Itraconazole (Azole) → histoplasmosis and aspergillosis
  • Fluconazole (triazole) → cryptococcal meningitis, candidiasis and coccidioidomycosis.
  • Voriconazole → Has interaction at CYP450 affecting drug breakdown. Inducers = griseofulvin & rifampicin, which increase the breakdown of the drug. Inhibitors = ketoconazole & fluconazole which decrease the breakdown of the drug.
  • Nystatin → GI use against candida and dermatophytes.
  • Griseofulvin → dermatophytosis
  • 5-flucytosine (antimetabolite) → systemic fungal infection, mainly candida and cryptococcus. Used with amphotericin B and itraconazole to treat long-term fungal skin infections.
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12
Q

What are the cellular targets of fungal cells (4)

A
  1. DNA, RNA & nucleic acid synthesis - nucleus
  2. Ergosterol - Cell membrane
  3. Glucans, mannans, chitons - Cell wall
  4. Squalene - cytoplasm
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