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Liz's Mycology Course > Yeast-Like Fungi (YLF) > Flashcards

Yeast-Like Fungi (YLF) Flashcards

1
Q

List various lab methods for identifying yeast isolates

A
  • Size and morphology
  • Germ tube
  • Fermentation (anaerobic)
  • Assimilation (aerobic)
  • Morphology on special media (e.g., pseudohyphae on cornmeal)
  • CHROMagar
  • Urease production
  • India ink
  • Latex agglutination
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2
Q

Name the test

- 2-3 hour incubation in rabbit plasma

A

Germ tube

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3
Q

Principle of CHROMagar

A

Chromogenic (color-producing) substrates; used to ID Candida spp

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4
Q

Fermentation test

A
  • Requires GAS PRODUCTION

- Tubes w/ single CHO (“purple broth sugars”) w/ Durham tube and oil on the surface

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5
Q

Fermentation test

- Pos/Neg result

A
  • Pos: acid production and gas production

- Neg: either no acid or gas production OR acid production but no gas production

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6
Q

Assimilation test

A

CHOs utilized as sole carbon source

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7
Q

Describe Candida albicans morphology on cornmeal agar

A

Pseudohyphae and chlamydoconidia (not always present)

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8
Q

Describe Candida tropicalis morphology on cornmeal agar

A

Pseudohyphae

  • Straight, long, graceful
  • “Starburst”
  • Blastoconidia along side of pseudohyphae
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9
Q

Describe Candida krusei morphology on cornmeal agar

A

Elongated blastoconidia (logs on a stream)

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10
Q

Describe Candida parapsilosis morphology on cornmeal agar

A

Pseudohyphae

- Crooked, tangled appearance

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11
Q

Describe Geotrichum morphology on cornmeal agar

A

Arthroconidia present

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12
Q

Describe Trichosporan morphology on cornmeal agar

A

Oval arthroconidia present

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13
Q

List the yeast that DO NOT produce pseudohyphae on cornmeal agar

A
  • Cryptococcus
  • Candida glabrata
  • Rhodotorula
  • Saccharomyces
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14
Q

Which yeast are urease positive?

A
  • Cryptococcus (all species)
  • Trichosporon
  • Rhodotorula
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15
Q

Which yeast are melanin on birdseed agar?

A

Cryptococcus neoformans

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16
Q

Which yeast are germ tube positive?

A

Candida albicans/dubliniensis

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17
Q

Which yeast are stained by India ink?

A

Cryptococcus spp

18
Q

Which yeast are trehalose positive?

A

Candida glabrata

19
Q

Which yeast are ascospore stain positive?

A

Saccharomyces

20
Q

Is CHROMagar a “rapid” test?

A

NO

21
Q

Is the germ tube test a “rapid” test?

A

YES! Incubates for 2-3 hours!

22
Q

Is the assimilation test a “rapid” test?

A

NO (needs to incubate 48-72 hours)

23
Q

Which yeast is #1 at causing human infection?

A

Candida albicans

24
Q

Which yeast should be associated w/ aggressive infections and treatment failures due to resistance?

A

Candida glabrata

25
Q

Candida krusei has ____ colonies on SAB

A

Dry

26
Q

Rhodotorula is what color pigment?

A

Red/red-orange

27
Q

Cryptococcus are ____ (if it’s encapsulated)

A

Mucoid

28
Q

Candida albicans causes what diseases?

A
  • Yeast infection
  • Can be involved w/ any part of the body (septicemia, UTI, vaginitis, oral thrush, etc.)
  • Normal flora of GI tract, vagina, and often skin
29
Q

Candida glabrata causes what diseases?

A

Diabetic urinary infections

30
Q

Cryptoccocus causes what diseases?

A

Pulmonary and CNS infections (meningitis)

- C. neoformans is a major pathogen in AIDS patients

31
Q

malassezia spp cause what diseases?

A

Systemic infections

- Associated w/ hyperalimentation (TPN) (lipids)

32
Q

Trichosporon causes what diseases?

A

“White piedra” → mat of mycelia around body hair; disseminated disease

33
Q

Cryptococcus neoformans

- Typical sources of infection

A

Associated w/ soil contamination w/ pigeon, turkey, or chicken droppings (inhalation)

34
Q

Cryptococcus neoformans

- Significance of isolation

A

Should always be considered significant until proven otherwise

35
Q

Cryptococcus neoformans

- Patient populations at increased risk

A

AIDS patients

36
Q

Cryptococcus neoformans

- Virulence factors

A
  • Adherence to mucosa

- Resistance to phagocytosis

37
Q

Typical morphology of Cryptococcus spp

A
  • Mucoid colonies (if encapsulated)

- Yeast cells appear larger, irregularly sized

38
Q

Sensitivities of latex agglutination vs. India ink preps for identifying C. neoformans

A

Latex agglutination is more sensitive than India ink

39
Q

Special culture requirements for Malassezia spp

A

Requires fatty acids (virgin olive oil) for growth

40
Q

Which yeast has a “spaghetti and meatball” morphology and fluoresces w/ infected skin lesions

A

Malassezia furfur

41
Q

Which species of yeast produce arthroconidia?

A
  • Trichosporon

- Geotrichum

42
Q

List the pathogenic yeasts

A
  • Candida
  • Cryptococcus
  • Trichosporon
  • Geotrichum
  • Rhodotorula
  • Malassezia
  • Yeast form of dimorphic

Liz's Mycology Course (8 decks)

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