PH1123 - fungi Flashcards
what does mycosis mean ?
a disease caused by infection with a fungus
what are three examples of a cutaneous disease ?
Tinea pedis (athlete’ s foot) Trichophyton rubrum Onychomycosis (nail infection) Trichophyton rubrum Tinea capitis (scalp ringworm) Trichophyton tonsurans
what are three examples of an opportunistic fungal disease ?
Candidosis (superfi cial/systemic) Candida albicans,
Candida glabrata, Candida parapsilosis
Aspergillosis Aspergillus fumigatus
Pneumonia Pneumocystis jirovecii (carinii)
Which of the following statement is correct?
Approximately there are 1000 distinct fungal species.
Approximately there are 40,000 distinct fungal species.
Approximately there are 90,000 distinct fungal species.
Approximately there are 100,000 distinct fungal species.
Approximately there are 150,000 distinct fungal species.
90000
Which of the following is an example a yeast? Trychophyton rubrum Candida albicans Aspergillus fumigatus Amphotericin B Piedraia hortae
Candida albicans
Which of the following statement about hyphae is correct?
Hyphae are fungal species associated with skin infections
Hyphae are long branching filamentous structure and a mode of vegetative growth
Hyphae are structures responsible for sexual or a sexual reproduction
Hyphae are structures responsible for spore production
Hyphae is a pathogen leading to chromoblastomycosis
Hyphae are long branching filamentous structure and a mode of vegetative growth
Which of the following statement is correct?
The term dimorphic means that a fungus can become a bacterium
The term dimorphic reflects cutaneous mycoses caused by a bacterium
The term dimorphic means a yeast can also form a mycelium
The term dimorphic means a bacterium can change shape depending on environmental conditions
The term dimorphic reflects systemic mycoses caused by a bacterium
The term dimorphic means a yeast can also form a mycelium
what type of cells are fungi? (4)
- eukaryotic
- spore-bearing
- absorptive nutrition (from ground)
- no chlorophyll
how do fungi reproduce?
- sexually and asexually
what is fungi cell wall made of?
- chitin
what is thallus?
- a body or vegetative structure of fungi
what are saprophytes?
- live on dead plant and animal material
what are parasites?
- live on/in living material
what are the types of fungal metabolism? (3)
- aerobic (generate ATP from glycolysis)
- facultative anaerobes-fermentation (make ethyl alcohol from glucose)
- obligate anaerobes (rumen of cattle)
what is ergosterol?
- unique sterol in the fungal membrane
what is chitin? (3)
- polymer of N-acetyl glucosamine
- make up 80% of the cell wall
- absent of mammalian cells
what is a target for antifungal chemotherapy?
- cell wall of fungi (chitin)
what does ergosterol do? (2)
- serves similar purposes to cholesterol in animal cell membranes
- makes the plasma membrane sensitive to antimicrobial agents which blocks the synthesis of ergosterol
Because ergosterol is present in cell membranes of fungi, yet absent in those of animals, it is a useful target for antifungal drugs.
what is the difference in the structure of cholesterol and ergosterol?
- no double bond between carbon 22 and 23 in cholesterol
what does sexual reproduction of fungi produce? (2)
- increased genetic diversity
- increased chance of survival
what happens in the asexual reproduction of fungi? (2)
- diploid yeast cell has a plentiful food supply
- this results in budding producing daughter diploid cells
what does asexual reproduction of fungi produce? (2)
- identical to mother cells
- no genetic diversity
what type of reproduction is diploid yeast cell? (2)
- budding
- asexual
what type of reproduction is haploid mould cell? (2)
- spore
- sexual
what is mould? (3)
- long branched thread-like filaments of cells (hyphae)
- hyphae form mycelium
- hyphae can be continuous or crossed walled-septa
what is mould enumeration?
- one single spore produces one new colony
what are fungal diseases called?
- mycoses
what are dimorphic fungi? (2)
- have both a yeast and mould (mycelial) form
- depending on environmental factors
what do dimorphic fungi depend on? (3)
- nutrients
- CO2
- temperature
what is the fungal specie associated with ring worm?
- tinea
what is tinea pedis?
- athlete’s foot
what is tinea cruris?
- jock itch
what is tinea captis?
- ringworm of the scalp
what is tinea corporis?
- ringworm of the body and nails
why is it important to apply cream on outside of inflammation as well as on the inflammation?
- to prevent fungi spreading
what is the dead part of a ringworm colony?
- the middle of the ringworm
what is candida albicans? (3)
- strict aerobe
- dimorphic
- normal microflora
how does Aspergillosis fumigatus usually enter the body?
- respiratory tract
why are fungi treatments difficult? (4)
- more similarity to humans
- drugs tend to be more toxic
- repeated applications
- lengthy treatments
what are antifungal drug targets and why? (2)
- proteins (enzymes); involved in fungal membrane synthesis (ergosterol), enzyme chitin synthase (cell wall)
- membranes; drugs interact with sterols
what is amphotericin B? (4)
- natural antifungal
- very broad spectrum of activity (yeasts and moulds)
- toxicity is a problem (v severe side effects)
- liposomal preparation; slow release to reduce toxicity
how does amphotericin B work? (3)
- treating systemic candidiasis with polyene antifungals
- binds to sterols primarily fungal cell membrane ergosterol
- binding disrupts osmotic integrity of fungal membrane causing leakage of intracellular potassium, magnesium, sugars and metabolites- treating systemic candidiasis with polyene antifungals
- binds to sterols primarily fungal cell membrane ergosterol
- binding disrupts osmotic integrity of fungal membrane causing leakage of intracellular potassium, magnesium, sugars and metabolites
what is itraconazole and how does it work? (2)
- active against moulds
- inhibits cytochrome P450 (P45014DM) that is an enzyme required in the sterol biosynthesis pathway
what are the side effects of itraconazole?
- caution with patients with high risk of heart failure
