Fungi Flashcards by Hannah Meiklejohn

Are fungi eukaryotic or prokaryotic? What is 1 main difference between fungi and plants?

Eukaryotic

Do not have chlorophyll

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What is S. cerevisiae?

Brewer’s/baker’s yeast

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What are the 3 classifications of fungi?

Unicellular (yeasts)
Filamentous (moulds)
Dimorphic

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What is the metabolic classification of unicellular fungi?

Facultative anaerobes

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How do unicellular fungi reproduce?

Asexually by budding

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How do unicellular fungi appear on agar?

Produce colonies

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What is the metabolic classification of filamentous fungi?

Aerobes

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How do filamentous fungi reproduce?

By conidia (asexual spores)

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How do filamentous fungi appear on agar?

Produce mycelia

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What are dimorphic fungi?

Can switch between unicellular and filamentous forms

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How big is the average yeast?

2-3um

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Are fungi saprophytes?

Mostly

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Give an example of a filamentous fungi

Penicillium

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How does filamentous fungi appear under the microscope?

Hyphae and conidia

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List the different types of fungi in order from most to least virulent

Dimorphic fungi
Dermatophytes
Agents of subcutaneous mycoses
Opportunists
Toxic fungi

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Give an example of a dimorphic fungus and the disease it causes

Histoplasma capsulatum

Causes “cave’s disease”

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Which of the fungis are primary pathogens?

Dimorphic fungi

Dermatophytes

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What makes dimorphic fungi good pathogens?

Can grow as filamentous fungi in environment, yeasts in body

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List 3 genera of dermatophytes

Microsporum
Trichophyton
Epidermophyton

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What type of fungi cause ringworm?

Dermatophytes

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Where do dermatophytes grow?

In keratin tissues (e.g. skin, hair, nails)

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How do dermatophytes cause symptoms? Which dermatophytes are more likely to cause symptoms than others?

Release metabolic by-products which can cause symptoms
Zoophilic dermatophytes (e.g. Microsporum canis) more likely to cause symptoms than anthropophilic (e.g. Trichophyton rubrum) dermatophytes

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What type of fungus causes tinea?

Dermatophytes

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Are agents of subcutaneous mycoses generally pathogenic? How are humans innoculated with these organisms?

Low grade pathogens

Innoculated directly onto the skin

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What is tinea corporis?

Tinea of the body

Give 3 examples of subcutaneous mycoses

Mycetoma Chromoblastomycosis Phaeohyphomycosis

What are bacterial mycetomas called?

Acintomycetoma

What is tinea cruris?

Tinea of the groin

What are fungal mycetomas called?

Eumycetoma

What is the proper name of mycetoma?

Maduromycosis

Give an example of an opportunistic mycoses

Candidiasis (caused by Candida albicans)

What is the most common acintomycetoma?

Nocardia spp.

What is the most common eumycetoma?

Madurella spp.

What are the 3 different types of candidiasis?

Mucocutaneous Chronic mucocutaneous (in those who can't clear pathogen) Systemic

Give 2 examples of agents responsible for cryptococcosis. Which of these are opportunistic?

C. neoformans | C. gattii (not necessarily opportunistic)

What are 1 of the defining features of a mycetoma?

Sulphur granules

What diseases are caused by cryptococcosis?

``` Pulmonary infection (usually mild) Meningitis (in immunocompromised, unless C. gattii) ```

Give an example of a toxic fungi

Aspergillus

List 3 presentations of aspergillosis

Saprophytic (fungus ball) Allergic Systemic

When does systemic candidiasis usually occur? What happens with a systemic infection?

``` With immunodeficiency (e.g. in neonates or HIV patients) Causes sepsis, can be fatal ```

What is pseudohyphae?

Hyphae without septa

Give an example of an organism that produce pseudohyphae

C. albicans

Give an example of a fungal AIDS-defining illness

Cryptococcal (fungal) meningitis

Does cryptococcus have a capsule?

Yes

What type of fungi is aspergillus?

Filamentous

What type of fungi is cryptococcus?

Yeast

What type of fungi is candida?

Yeast

How are fungal infections diagnosed?

``` Microscopy Culture Ag detection PCR (pan-fungal if not sure if fungal infection) Other (e.g. mass spectrometry) ```

List 4 systemic drugs used in anti-fungal chemotherapy. Give an example of each

Polyenes (e.g. amphotericin B) Triazoles (e.g. fluconazole, voriconazole) Echinocandins (e.g. capsofungin) 5-fluorocytosine

How can fungi be distinguished?

By conidia (have to grow under special conditions)

What is an India ink stain?

Negative stain

How can skin be viewed with microscopy?

Normally opaque under microscope; keratin must be dissolved

What is the characteristic microscopic feature of epidermophyton?

Distinctive appearance of macroconidia

What is the "quick and dirty" test for C. albicans?

Germ tubes; make pseudohyphae in the lab (usually in horse serum)

What diagnostic method is often used for cryptococcus?

Ag detection (detect capsular Ag in CSF, can be used to monitor treatment)

What is the drawback of amphotericin B?

Very toxic

List 2 classes of topical anti-fungal chemotherapeutic agents and give examples of each

Polyenes (e.g. nystatin) | Imidazoles (e.g. clotrimazole)

What are the 2 main targets of anti-fungals?

Ergosterol | Nucleic acids

What is ergosterol?

Sterol found specifically in fungal cytoplasmic membranes

What do polyenes act on?

Bind to ergosterol to disrupt integrity of fungal cell membrane

What is the mechanism of action of allylamines, triazoles and morpholines?

Affect synthesis of ergosterol

Why are polyenes so toxic?

Also bind to cholesterol and disrupt host cell membranes

How are polyenes usually administered?

What is the mechanism of action of 5-flurocytosine?

Prodrug that is metabolised to 5-flurouracil in the body | Affects DNA and RNA synthesis

How is 5-flurocytosine selectively for fungi?

Only fungi have cytosine deaminase to activate the drug

What is the drawback of 5-flurocytosine?

Resistance occurs readily

What drug is usually used to treat Candida spp.?

Fluconazole

What drugs are usually used to treat cryptococcus?

Amphotericin B + 5-flurocytosine

What drug is usually used to treat Aspergillus?

Voriconazole

What drug is usually used to treat dimorphic fungi?

Amphotericin B

What topical agents are usually used to treat dermatophytes?

Terbinafine ("Lamisil) Clotrimazole ("Canesten") Amorolfine ("Loceryl"

What orally administered agents are usually used to treat dermatophytes?

Terbinafine Fluconazole Griseofulvin (most toxic)

When are orally administered agents used to treat dermatophytes?

When infection is difficult to treat topically or is widely disseminated on the skin Also if in nails (grows slowly, have to treat topically for a long time - oral treatment may be preferred to somewhat reduce treatment time)

Fungi Flashcards

(73 cards)