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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
Q

Mycophycomycota

A

Mychorhyzial fungi that have mutualism with tree roots

- truffles

26
Q

Which class is known as the bread or pin molds?

A

Zygomycetes

  • fast growing, terrestrial, saprobic
  • non motile cells
  • identification based on sporangial morphology
27
Q

Entomophthoromycosis

A

Entomophthorales subcutaneous zygomycosis

  • Conidiobolus and Basidiobolus
  • occurs in horses
28
Q

Mucormycosis

A

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
Q

Which classification is known as mushrooms and toadstools?

A

Basidiomycetes

  • saprobes and parasites
  • dolipores allow cytoplasmic migration
  • main concern with toxicities
30
Q

Filobasidiella

A

Teleomorphs of known pathogenicity

31
Q

Basidiomycosis

A

Coprinus and Schizophyllium

32
Q

Mushroom poisoning

A

Aminita, Lepiotia, Coprinus, Psilocybe

33
Q

What is the common mold?

A

Ascomycetes

  • saprobes, parasites, lichen forming
  • no current classes, have been grouped on how asci were arranged
  • most pathogens!
34
Q

Medically important Ascomycetes

A

Teleomorphs of known pathogenic fungi:

  • Arthroderma
  • Nannizzia
  • Ajellomyces
  • Pseudallescheria
  • Eurotium
35
Q

Agents of mycetoma

A

Leptosphaeria and Neotestudina

36
Q

Black piedra

A

Piedraia hortae

37
Q

What are known as conidial molds?

A

Hyphomycetes

  • class of mycelial moulds, mostly comprised of Ascomycetes
  • no sexual state is present
38
Q

Dermatiaceous hyphomycetes

A

Produce dark brown, green-black, or black colonies

- causative agents of phaeohyphomycosis

39
Q

Hyaline hyphomycetes

A

Are not darkly pigmented, colonies may be colorless or brightly colored
- agents of hyalohyphomycosis, aspergillosis, dermatophytosis, and dimorphic pathogens (Histoplasma capsulatum)

40
Q

What is the only motile fungi?

A

Chytridiomycetes

- only causes disease in amphibians!

41
Q

Epidermal changes due to _____ have been found in sick/dying adult anurans during mass mortality events associated with significant population declines

A

Chytridiomycete fungus

- associated with morbidity and mortality in wild and captive anurans from around the world

42
Q

Cutaneous chytridiomycosis

A

Fatal disease of anurans

- proximate cause of recent amphibian declines

43
Q

Chytridiales general characteristics

A
  • waterborne
  • pathogenic to adult amphibians, does not kill tadpoles but they are carriers
  • prefers cooler temperatures
44
Q

Chytridiomycosis pathogenesis

A
  • hyperkeratosis
  • sloughing and erosion of epidermis
  • occasional ulcerations
45
Q

Fungi that cause disease differ from taxonomically similar species by:

A
  • surviving and growing at higher (body) temperatures
  • growing in reduced oxidation-reduction environments of tissue
  • overcome host defenses
46
Q

The best example of transient adaptation to invasion and growth within tissue is _____

A

Dimorphic fungi

47
Q

What are common fungal diseases that are non beneficial to either the host or the fungus?

A
  • histoplasmosis
  • blastomycosis
  • coccidiomycosis
  • sporotrichosis
48
Q

Cryptococcus neoformans

A

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
Q

Which species produces keratin and can establish equilibrium with some hosts?

A

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
Q

Which species gain entry into the body by traumatic implantation?

A

Subcutaneous mycoses

- limited invasive ability

51
Q

What are some predisposing factors that may contribute to opportunistic fungal infection?

A
  • prolonged administration of antibiotics
  • administration of immunosuppressive agents or cytotoxic drugs
  • immune deficiencies, cancer, diabetes, or recent surgery
52
Q

Most fungal infections are chronic _______

A

Granulomas

- easily mistaken for tumors, bacterial disease, or non-infectious processes

53
Q

What is the most useful tool for the diagnosis of fungal disease?

A

Appearance of the organism in tissue, aspirates, or exudates!!!

54
Q

What is the only efficacious resistance to fungal infection?

A

Cellular defenses

- humoral antibodies play no role in fungal infections

55
Q

Common points of entry for fungi

A
  • lung (most common)
  • skin
  • gastrointestinal tract
56
Q

Most fungi will grow within

A

Phagocytic cells

  • are facultative intracellular organisms
  • disseminate to other body parts via lymphatics and blood
57
Q

With primary infection _____ immunity prevails, while with progressive disease development, _______ immunity plays a large role

A

Cellular; delayed hypersensitivity

58
Q

What is one fungus in which the host response is minimal or nonexistent?

A

Cryptococcosis

Infectious Agents 2 (29 decks)

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