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Fungi Flashcards

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1
Q

What are 5 features of the fungi kingdom?

A
  1. Eukaryotic
  2. Larger and more complex than bacteria
  3. Cell wall (ergosterol present)
  4. lack chlorophyl
  5. reproduce asexually or sexually
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2
Q

How are fungi classified?

A

based on structures formed during sexual reproduction

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3
Q

What class of fungi do not form sexual structures?

A

The deuteromycetes

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4
Q

Are yeasts multi or single celled?

A

single celled

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5
Q

What are chains of yeast cells called?

A

pseudohyphae

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6
Q

How do yeast reproduce?

A

By budding to form daughter cells/blastopores

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7
Q

Are yeast commensal or pathogenic?

A

there are some of both

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8
Q

Are moulds multi or single celled?

A

multicellular

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9
Q

What structures do moulds form?

A

Tubular structures called hyphae which have either cross walls (called septate) or lack cross walls (aseptate)

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10
Q

What are asexual spores formed by moulds called? what do they give rise to?

A

conidiophores giving rise to conidia

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11
Q

What are arthrospores?

A

Fragmented hyphae that form spores

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12
Q

What are dimorphic fungi?

A

fungi that can behave as either yeast or mould depending on the temperature

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13
Q

What is the temperature differential for mould vs. yeast in dimorphic fungi?

A

grow as mould at RT

Yeast at elevated temps

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14
Q

What form of dimorphic fungi is typically found in the body vs the environment?

A

mould in the environment

yeast in the body

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15
Q

Can dimorphic fungi be passed person to person?

A

no because the form in the body is yeast which doesnt produce spores

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16
Q

What tends to limit the mould form of dimorphic fungi?

A

geographical distribution

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17
Q

Where can the yeast form of dimorphic fungi sometimes be seen ?

A

stained tissue samples

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18
Q

What are 4 ways in which fungi cause disease?

A
  1. growth on body surfaces
  2. Invasion of the body
  3. Allergic reactions by the body
  4. Toxins released after ingestion
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19
Q

What fungi is often a commensal of mucous membranes in the GI tract but can rapidly colonize damaged skin

A

Candida albicans

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20
Q

the sites of Candida infections by C. albicans tend to be?

A

mucocutaneous

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21
Q

What are two common forms of candidiasis?

Study These Flashcards
A

oral and vaginal

22
Q

What are 3 possible presentations of oral candidiasis?

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A
  1. thrush
  2. Stomatitis: denture sore mouth
  3. Chelitis: angular erosions with pustules
23
Q

What is the vaginal presentation of candidiasis like?

Study These Flashcards
A

similar to thrush

24
Q

What are 3 presentations of skin infections by Candida albicans?

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A

Interigo: between toes

Diaper rash: due to ammonia from urine irritating the skin and allowing the candida in

Nail

25
What are 3 systemic infections that candida are often associated with?
1. Urinary tract - due to use of foley catheters 2. Endocarditis - especially with prosthetic heart valves or IV drug use 3. Septicemia in immunosuppressed patients
26
What are two lab methods of diagnosing candida infections
1. Microscopy - KOH or gram stain 2. Culture
27
What is an encapsulated yeast endemic to BC and found in bird droppings?
Cryptococcus neoformans and C. gattii
28
What 2 things does infection with C. neoformans/gattii cause ?
1. Pneumonia - subclinical 2. Meningitis - chronic
29
What widely distributed yeast causes pneumonia in immunosuppressed patients?
Pneumocystis jirovecii
30
What is the closely related group of keratolytic (attack skin, hair, nails) fungi
Dermatophytes
31
What is the pathogenesis for an infection with a dermatophyte?
1. minor trauma to skin = initial infection | 2. Fungal penetration balances turnover of superficial skin squamous cells
32
What 2 factors predispose someone to develop a dermatophyte infection?
1. Minor trauma | 2. Occlusion: no drying of skin. Moisture reduces harshness of skin environment
33
What are some clinical features/presentations of a dermatophyte infection?
1. Red, scaly, rash with pustules (maybe) | 2. Central clearing and migrating margin
34
How are dermatophyte infections passes?
Infected skin squames that contaminate fomites | - rarely by direct contact
35
What is the name given to skin infections typically caused by dermatophytes?
Tinea (capitis, pedis...)
36
How are dermatophyte infections identified?
1. culture - looking for pigment of colonies | 2. growth on plates - looking for macro and microconidia
37
What fungi is the cause of tinea versicolor?
Malassezia furfur
38
What is M. furfur?
A widepread skin commensal that flourishes by feeding on skin fatty acids
39
What is the presentation of Tinea versicolor?
Infection is superficial, and manifests as hyper- or hypo- pigmented lesions with itching, and occasional pustules.
40
How is an infection with M. furfur often identified?
through microscopy - looking for the characteristic spaghetti and meatballs pattern of yeast cells
41
Invasive infection causing fungi can often be divided into two groups... give some examples
1. Opportunistic fungi (widely occurring) - Aspergillus spp., Pneumocystis jirovecii, Candida spp. 2. Geographically defined - dimorphic fungi - Histoplasma capsulatum
42
Where can Aspergillus fumigatus be found?
pretty widespread on rotting vegetation spores are commonly present in the air
43
What is an important predisposing factor to disease being caused by A. fumigatus?
immunosuppression
44
What are 3 clinical presentations of Aspergillus fumigatus?
1. Allergic bronchiopulmonary - Asthma-like symptoms. - Fungus grows in bronchial secretions. 2. Fungal ball in cavities of lungs and sinuses 3. Invasive disease - tissue destruction and pneumonia
45
What lab techniques are used to diagnose invasive fungal infections?
Microscopy - secretions/KOH - histology Culture but multiple positives may occur due to contamination
46
What kind of fungus is Histoplasma capsulatum? Morphology?
dimorphic fungus doesn't actually have a capsule!
47
Where is Histoplasma capsulatum found
Central United States, especially the Mississippi river valley and Southern States, north to Ontario, Montreal.
48
How does an infection with H. capsulatum occur?
Spores are inhaled and germinate in the lung
49
What proportion of people infected with Histoplasma capsulatum develop disease? how is it detected?
only a small portion identification by serology
50
What is characteristic of Histoplama capsulatum in culture?
Growth of cells with extensions

Clinical Micro (28 decks)

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