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Infectious Agents 2 > Intro to Mycology > Flashcards

Intro to Mycology Flashcards

1
Q

General characteristics of fungi

A
  • aerobic
  • non-photosynthetic (lack chlorophyll)
  • grow well at room temperature
  • prefer dark, moist environments
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2
Q

Do fungi have a true cell wall?

A

Yes, contains cellulose and chitin

  • carb polymers (glucans, mannans) = 50-60% of cell wall
  • 5-10% protein
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3
Q

Are antibiotics that attack the cell wall useful against fungi?

A

No!

  • are eukaryotes with nuclei, membranes, and ribosomes resembling mammals
  • chemotherapeutics against fungi may damage the host
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4
Q

What do fungi cell walls contain instead of cholesterol?

A

Ergosterol

  • common in mammalian membranes or phosphoglycerides
  • helps define apical and basal aspect of cells (helps with cell orientation)
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5
Q

Saprophytes

A

Associated with soil or parasites of plants

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6
Q

How do fungi infect animals?

A

Chance occurrence due to inhalation, ingestion, penetration of wounds

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7
Q

Are fungal infections contagious?

A

Rarely, other than ringworm

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8
Q

What is the important of sexual stages?

A

Only important in establishing taxonomy and classification of individual fungi

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9
Q

What is important in identifying fungal isolates?

A

Asexual structures (conidia)

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10
Q

Dimorphic

A

Exist as both yeasts and hyphae

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11
Q

Yeast

A

Single celled eukaryotic form

- multiply asexually via budding

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12
Q

Hyphae

A

Mutlicellular with a thick cell wall

  • long branching filaments
  • bear conidia
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13
Q

Mycelium

A

Mass of hyphae

- single multicellular life form (aka: colony, thallus)

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14
Q

Septate

A

If the hyphae contain crosswalls

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15
Q

Aseptate

A

If the hyphae do not contain crosswalls

- aka: coenocytic

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16
Q

Thermal dimorph

A

A yeast at 37 C or in animal tissues (aka: parasitic phase) and is a mycelium at room temperature (aka: environmental, or filamentous phase)
- conversion from one to the other is due to a change in temperature, NOT a change in host!

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17
Q

Tissue dimporhs

A

Fungi that convert from mycelial phase to yeast phase due to factors in animal tissue
- phase conversion is not related to temperature, is only accomplished in the lab with artificial media

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18
Q

Conidia

A

Cells that are the product of asexual multiplication

  • functionally similar to seeds of higher plants
  • are not as resistant as bacterial endospores
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19
Q

Sporangium

A

Sac like structure that some conidia are born in

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20
Q

Macro versus microconidia

A
  • macro: large and multicellular

- micro: small and one celled

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21
Q

Conidia produced as buds from hyphal parent

A

Microconidia

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22
Q

Arthroconidia

A

When hyphal cells form conidia and fragment

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23
Q

What are the 4 major subdivisions of fungi?

A
  • zygomycota
  • ascomycota
  • chytridiomycota
  • basidiomycota
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24
Q

Deuteromycota

A

Fungi without a known perfect state

- may represent asexual stages (anamorphs) of either Basidiomycota or Ascomycota

25
Mycophycomycota
Mychorhyzial fungi that have mutualism with tree roots | - truffles
26
Which class is known as the bread or pin molds?
Zygomycetes - fast growing, terrestrial, saprobic - non motile cells - identification based on sporangial morphology
27
Entomophthoromycosis
Entomophthorales subcutaneous zygomycosis - Conidiobolus and Basidiobolus - occurs in horses
28
Mucormycosis
Mucorales, subcutaneous and systemic zygomycosis - Rhizopus, Mucor, Rhizomucor, Absidia, Cunninghamella, Mortierella, Saksenaea, Apophysomyces = mycotic ruminitis/placentitis --> grows on mucosal surfaces, ends with abortion or ruminitis
29
Which classification is known as mushrooms and toadstools?
Basidiomycetes - saprobes and parasites - dolipores allow cytoplasmic migration - main concern with toxicities
30
Filobasidiella
Teleomorphs of known pathogenicity
31
Basidiomycosis
Coprinus and Schizophyllium
32
Mushroom poisoning
Aminita, Lepiotia, Coprinus, Psilocybe
33
What is the common mold?
Ascomycetes - saprobes, parasites, lichen forming - no current classes, have been grouped on how asci were arranged - most pathogens!
34
Medically important Ascomycetes
Teleomorphs of known pathogenic fungi: - Arthroderma - Nannizzia - Ajellomyces - Pseudallescheria - Eurotium
35
Agents of mycetoma
Leptosphaeria and Neotestudina
36
Black piedra
Piedraia hortae
37
What are known as conidial molds?
Hyphomycetes - class of mycelial moulds, mostly comprised of Ascomycetes - no sexual state is present
38
Dermatiaceous hyphomycetes
Produce dark brown, green-black, or black colonies | - causative agents of phaeohyphomycosis
39
Hyaline hyphomycetes
Are not darkly pigmented, colonies may be colorless or brightly colored - agents of hyalohyphomycosis, aspergillosis, dermatophytosis, and dimorphic pathogens (Histoplasma capsulatum)
40
What is the only motile fungi?
Chytridiomycetes | - only causes disease in amphibians!
41
Epidermal changes due to _____ have been found in sick/dying adult anurans during mass mortality events associated with significant population declines
Chytridiomycete fungus | - associated with morbidity and mortality in wild and captive anurans from around the world
42
Cutaneous chytridiomycosis
Fatal disease of anurans | - proximate cause of recent amphibian declines
43
Chytridiales general characteristics
- waterborne - pathogenic to adult amphibians, does not kill tadpoles but they are carriers - prefers cooler temperatures
44
Chytridiomycosis pathogenesis
- hyperkeratosis - sloughing and erosion of epidermis - occasional ulcerations
45
Fungi that cause disease differ from taxonomically similar species by:
- surviving and growing at higher (body) temperatures - growing in reduced oxidation-reduction environments of tissue - overcome host defenses
46
The best example of transient adaptation to invasion and growth within tissue is _____
Dimorphic fungi
47
What are common fungal diseases that are non beneficial to either the host or the fungus?
- histoplasmosis - blastomycosis - coccidiomycosis - sporotrichosis
48
Cryptococcus neoformans
One of the few fungi that produce capsules, except as a yeast - when inhaled, it colonizes in nasal mucosa or can become inoculated into a wound --> produces a huge capsule and becomes a space occupying mass
49
Which species produces keratin and can establish equilibrium with some hosts?
Dermatophytoses - specialized saprophytes that do not invade living tissue (feed only on dead cornified appendages) - clinical disease is a toxic/allergic response to the presence of the organism and its metabolic byproducts
50
Which species gain entry into the body by traumatic implantation?
Subcutaneous mycoses | - limited invasive ability
51
What are some predisposing factors that may contribute to opportunistic fungal infection?
- prolonged administration of antibiotics - administration of immunosuppressive agents or cytotoxic drugs - immune deficiencies, cancer, diabetes, or recent surgery
52
Most fungal infections are chronic _______
Granulomas | - easily mistaken for tumors, bacterial disease, or non-infectious processes
53
What is the most useful tool for the diagnosis of fungal disease?
Appearance of the organism in tissue, aspirates, or exudates!!!
54
What is the only efficacious resistance to fungal infection?
Cellular defenses | - humoral antibodies play no role in fungal infections
55
Common points of entry for fungi
- lung (most common) - skin - gastrointestinal tract
56
Most fungi will grow within
Phagocytic cells - are facultative intracellular organisms - disseminate to other body parts via lymphatics and blood
57
With primary infection _____ immunity prevails, while with progressive disease development, _______ immunity plays a large role
Cellular; delayed hypersensitivity
58
What is one fungus in which the host response is minimal or nonexistent?
Cryptococcosis

Infectious Agents 2 (29 decks)

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