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Mycology > Yeast > Flashcards

Yeast Flashcards

1
Q

Yeast General Info

A

Normal flora of the oropharynx, GI tract, and urogenital tract
Unless predominant numbers are clinical insignificant

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2
Q

Candida albicans Colony Morphology

A

Cream colored, pasty, smooth colony
May form spider-like or starry-feet projections with age

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3
Q

Candida albicans Microscopic

A

After 3 days - pseudohyphae with clusters or round blastoconidia form at the septa and large, thick walled, terminal chlamydospores develop
37 C - inhibits chlamydospores

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4
Q

Candida albicans Pathogenicity

A

1) Mucocutaneous Candidiasis - oral cavity (thrush), vaginal canal, trachea, and bronchi
2) Cutaneous Candidiasis - infection of skin and involves moist areas like fingers, toes, armpits, etc
3) Systemic Candidiasis - rare condition of debilitating, neoplastic, or immunosuppressive diseases

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5
Q

Candida albicans Germ Tube

A

Positive
C. albicans var stellatoidea may also give a positive

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6
Q

Candida tropicalis Colony Morphology

A

Creamy with mycelial fringe (looks like fungus on edges)

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7
Q

Candida tropicalis Microscopic

A

After 3 days - blastoconidia singly or in pairs of very small groups along pseudohyphae. A few teardrop shaped chlamydospores.
“Mickey Mouse Ears”

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8
Q

Candida tropicalis Pathogenicity

A

Cause infections in patients with:
1) Breakdown of body’s immune system
2) Prolonged treatment with antibiotics, corticosteroids, or cytotoxic drugs
3) Diabetes mellitus
4) Drug addicts
5) Found without evidence of disease

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9
Q

Candida tropicalis Germ tube

A

Negative

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10
Q

Candida parapsilosis Colony Morphology

A

Creamy, sometimes develops a lacy appearance

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11
Q

Candida parapsilosis Microscopic

A

After 3 days - round to oval blastoconidia formed singly or in small clusters are seen along the pseudohyphae
Large hyphal elements called giant cells may be present

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12
Q

Candida parapsilosis Pathogenicity

A

Considered nonpathogenic
Has been known to cause infection in susceptible individuals

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13
Q

Candida parapsilosis Germ tube

A

Negative

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14
Q

Candida kefyr Colony Morphology

A

Creamy and smooth

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15
Q

Candida kefyr Microscopic

A

3 days - forms pseudohyphae with found to elongate blastoconidia that can become detached from pseudohyphae
“logs in a stream”

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16
Q

Candida kefyr Pathogenicity

A

Usually nonpathogenic
May cause infection in susceptible individuals

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17
Q

Candida kefyr Germ tube

A

Negative

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18
Q

Candida krusei Colony Morphology

A

Flat, dry, dull
Developing a mycelial fringe

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19
Q

Candida krusei Microscopic

A

3 days - form pseudohyphae with elongate blastoconidia creating a cross-match sticks or treelike appearance

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20
Q

Candida krusei Pathogenicity

A

Nonpathogenic
May cause infections in susceptible individuals

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21
Q

Candida krusei Germ tube

A

Negative

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22
Q

Candida krusei Urease test

A

Positive

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23
Q

Candida guilliermondi Colony Morphology

A

Flat, glossy, smooth, edged, cream color, may develop slight pink color with age

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24
Q

Candida guilliermondi Microscopic

A

3 days - forms small yeast cells and relatively few short pseudohyphae often having small clusters of blastoconidia at septa

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25
Q

Candida guilliermondi Pathogenicity

A

Nonpathogenic
May cause infection in susceptible individuals

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26
Q

Candida dubliniensis Colony Morphology

A

Cream colored, pasty, smooth

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27
Q

Candida dubliniensis Microscopic

A

Chlamydoconidia are often attached at end of short, hyperbranching pseudohyphae and in a characteristic triplet or pair arrangement

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28
Q

Candida dubliniensis Pathogenicity

A

Primarily associated with HIV patients
Concern that this is more virulent than C. albicans - developing fluconazole resistance

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29
Q

Candida dubliniensis Germ tube

A

May be positive

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30
Q

Candida dubliniensis Chromagar

A

Colonies are green but lighter than C. albicans

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31
Q

Candida auris General Info

A

Emerging pathogen originally isolated in Asia
Antifungal resistance is common
Easily transmissible from person to person

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32
Q

Candida auris first isolation

A

Ear canal of patient in Japan

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33
Q

Trichosporon species

A

Two of interest:
1) T. beiglii
2) T. capitatum

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34
Q

Trichosporon Colony Morphology

A

Yeastlike
At first cream colored, moist, soft
Later finely wrinkled, heaped, and darkens to yellowish-grey

35
Q

Trichosporon species Microscopic

A

3 days - true hyphae and pseudohyphae with blastoconidia singly or in short chains.
Arthroconidia form on older cultures

36
Q

Trichosporon species Pathogenicity

A

T. beiglii causes white piedra
Occurs almost exclusively in immunocompromised patients

37
Q

Trichosporon species Germ tube

A

Negative

38
Q

Trichosporon species Urease test

A

Positive

39
Q

Geotrichum candidum Colony Morphology

A

Young colonies: white, yeast-like
Mature colonies: Submerged hypae at periphery giving ground glass appearance
Most strains do NOT grow at 37 C

40
Q

Geotrichum candidum Microscopic

A

3 days - true hyphae form that segment into rectangular arthroconidia, varying in size
NO blastoconidia along hyphae
NO alternating of light/dark

41
Q

Geotrichum candidum Pathogenicity

A

Causes geotrichosis - rare infection that may produce lesions in the mouth, intestines, and lungs
Cause disease mostly in immunocompromised hosts

42
Q

Cryptococcus neoformans General Info

A

Widely distributed in soil mixed with excreta from poultry
Common infection in AIDS population

43
Q

Cryptococcus neoformans Colony Morphology

A

Begins as smooth white to tan colony, may become mucoid
Cream to brown with age
“Stringy” when trying to remove colony

44
Q

Cryptococcus neoformans Microscopic

A

No pseudohyphae,
Irregular sized, spherical, thick-walled yeast cells with spaces between them

45
Q

Cryptococcus neoformans Urease

A

Positive

46
Q

Cryptococcus neoformans Nitrate

A

Positive

47
Q

Cryptococcus neoformans India Ink

A

Positive for capsule

48
Q

Cryptococcus neoformans Niger Seed Agar

A

Positive
Detects phenol oxidase production of yeast resulting in production of melanin
Red-brown pigment

49
Q

Cryptococcus neoformans Pathogenicity

A

Cryptococcosis
Subacute or chronic infection most frequently involving CNS (meningitis)
AIDS patients

50
Q

Cryptococcus albidus General Info

A

Common transient on human skin and has been reported as rare cause of pulmonary, CNS, and vaginal infections

51
Q

Cryptococcus albidus Colony Morphology

A

Cream colored
Smooth to mucoid
Yeast-like

52
Q

Cryptococcus albidus Microscope

A

SAB - demonstrates globose to avoid budding yeast-like cells or blastoconidia

53
Q

Cryptococcus albidus India Ink

A

Positive

54
Q

Cryptococcus albidus Urease

A

Positive

55
Q

Cryptococcus laurentii General Info

A

Rare cause of pulmonary and cutaneous infection and continuous ambulatory peritoneal dialysis (CAPD)

56
Q

Cryptococcus laurentii Colony Morphology

A

Cream colored, sometimes a deeper orange-yellow with age
Smooth mucoid texture

57
Q

Cryptococcus laurentii Microscopic

A

SAB - produces spherical and elongated budding yeast-like cells or blastoconidia

58
Q

Cryptococcys laurentii India Ink

A

Positive

59
Q

Cryptococcus laurentii Urease

A

Positive

60
Q

Candida glabrata Colony Morphology

A

Small yeast-like colonies
Pasty, smooth
White to cream

61
Q

Candida glabrata Microscopic

A

CM 3 days - demonstrates only small, round to oval, single terminal budding
Nonencapsulated yeast cells, tend to form compact clusters
No pseudohyphae

62
Q

Candida glabrata

A

Assimilates only glucose and trehalose

63
Q

Candida glabrata Pathogenicity

A

Causes torulopsosis
Infection occurring usually in blood stream or UTI, sometimes in the lungs

64
Q

Rhodotorula species Colony Morphology

A

Pink to coral
Yeast-like
Soft and smooth

65
Q

Rhodotorula species Microscopic

A

CM 3 days - demonstrates budding round or oval cells variable in size with rare rudimentary pseudohyphae
No ascospores

66
Q

Rhodotorula species Urease

A

Positive

67
Q

Rhodotorula species Pathogenicity

A

Associated with contaminated equipment such as catheters, contaminated IV solutions and brochioscopes
Infections are present in terminal stages of debilitating disease

68
Q

Saccharomyces species Colony Morphology

A

Smooth, moist
White to cream colored

69
Q

Saccharomyces species Microscopic

A

CM 3 days - demonstrates yeast cells of various shapes with multilateral budding
Few very short pseudohyphae

70
Q

Saccharomyces species Kinyoun stain

A

Characteristic ascospores seen when stained with Kinyoun and grown on special media

71
Q

Saccharomyces species Pathogenicity

A

Usually nonpathogenic
Has been implicated in various infections in predisposed individuals

72
Q

Prototheca wicherhamii Colony Morphology

A

Soft, wet yeastlike
White to light tan colonies

73
Q

Prototheca wicherhamii Microscopic

A

Large non-budding cells with a symmetrical morula-like structure
Organism resembles algae Chlorella

74
Q

Prototheca wicherhamii Pathogenicity

A

Previously thought to be a skin saprophyte
Now identified as rare opportunistic pathogen

75
Q

Malssezia furfur General Info

A

Cause of tinea versicolor
Characterized by superficial scaly areas
Lesions occur on smooth surfaces of body
Causes disseminated infection in infants and young children

76
Q

Malassezia furfur Colony Morphology

A

Organism will grow in yeast form only when media has been overlaid with 1-2 ml of olive oil

77
Q

Malassezia furfur Microscopic

A

CM 3 days - no pseudohyphae or true hyphae formed
Round to oval cells
Conidia are produced on a broad base (shoulders may be seen)

78
Q

Germ Tube Positive Organisms

A

Candida ablicans
Candida dubliensis - some strains, not all

79
Q

Trichosporon species

A

Hyphae present
Arthroconidia positive
Urease positive

80
Q

Candida species

A

Hyphae present
Blastoconidia positive

81
Q

Cryptococcus species

A

Hyphae not present
Urease positive
Inositol assimilation
Nitrate positive

82
Q

Rhodotorula species

A

Hyphae not present
Urease positive
Inositol negative

83
Q

Candida glabrata

A

Hyphae not present
Urease negative
Small cells on Cornmeal
Dextrose positive
Trehalose positive

Mycology (9 decks)

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