Fungal Fundamentals Flashcards

1
Q

two forms of pathologic fungi

A

**morphological terms but no taxonomic significance; some organisms are dimorphic (yeast when warmer, moulds when colder)
-moulds
-yeasts

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2
Q

Microbiological characteristics

A

-nucleated
-fungal hyphae (cell walls composed with chitin)
-cell membranes- contain ergosterol as main sterol

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3
Q

Environments

A

-aerobic
-grow at low temp (20-30C)
-high pressure
-low pH
-play a role in carbon cycle
-degrad polymers (biopolymers in wood, synthetic polymers)

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4
Q

Virulence factors

A
  1. tissue invasion
    -mycosis
  2. Toxin production
    -mycotoxicosis
  3. Hypersensitivity
    -moulds grow in damp buildings; exacerbate asthma or hypersensitivity pneumonitis
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5
Q

Mycotoxicosis

A
  1. Aflatoxicosis- aflatoxins in feed affect poultry
  2. Fusariotoxicosis- zearalenone is non toxic for poultry but causes disease in pigs
  3. Ergotism- alkaloids produced by fungi growing on cereals
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6
Q

Taxonomy

A

-based on morphology and sexual reproductive cycles
-increasingly relying on DNA sequencing

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7
Q

Hyphae

A

filaments which make up mycelium

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8
Q

Mycelium

A

a mat of branching hypha

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9
Q

Asexual spores

A

disseminated to other locations and germinate when conditions are favourable
-spores will develop on different structures with different morphologies

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10
Q

Pathogenicity of fungi

A

Very few are pathogenic to mammals
-fungi are opportunistic not contagious
*Dermatophytes are common and contagious
-common cause of disease in ectotherms (plants, insects, fish, amphibians)
-not much effect on endotherms because body temperature is high

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11
Q

Fungi in mammals

A
  1. Commensal/host associated
    -disease in states of immunosuppression
    -candida, Malassezia
  2. Environmentally acquired
    -dimorphic fungi
    -disease following exposure to large inoculum
    -Blastomyces
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12
Q

Dinosaurs and fungal impact

A

-nuclear winter from asteroid killed plants
-large scale deforestation at K/T boundary; fungal breakdown of plants
-dinosaurs loss of plants, inability to warm up (ectotherms), immunosuppression and massive fungal spore plumes

-warm blooded animals (early mammals and birds) were protected by higher temp and ability to eat seeds

**Epidemiological Triad

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13
Q

White nose syndrome in North American Bats

A

-caused by Pseudogymnoascus destructans
-first studies at Usask
-huge mortality in bats

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14
Q

Chytridiomycosis

A

-threatens amphibians on every continent
-caused by Batrachonchytruym dendrobatidis; thought to originate in Xenopus laevis which were resistant and were able to pass it on

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15
Q

Snake fungal disease

A

-emerging in US but found in museum specimens in 1940s
-caused by Ophidiomyces ophiodiicola
-hard to find impact because snakes are reclusive animals

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16
Q

Fungal disease in people

A

Linked with immunosuppression, organ transplant recipients, SLE (lupis), vascular diseases, diabetes mellitus, alcoholics, drug users, AIDS, latrogenic factors (antimicrobial, steroid use)

17
Q

Treatment

A

-difficult to treat
-Most common: use the azoles (Aspergillus, candida)
-many others on table in notes?

*no susceptibility testing really available