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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
Candida guilliermondi Pathogenicity
Nonpathogenic May cause infection in susceptible individuals
26
Candida dubliniensis Colony Morphology
Cream colored, pasty, smooth
27
Candida dubliniensis Microscopic
Chlamydoconidia are often attached at end of short, hyperbranching pseudohyphae and in a characteristic triplet or pair arrangement
28
Candida dubliniensis Pathogenicity
Primarily associated with HIV patients Concern that this is more virulent than C. albicans - developing fluconazole resistance
29
Candida dubliniensis Germ tube
May be positive
30
Candida dubliniensis Chromagar
Colonies are green but lighter than C. albicans
31
Candida auris General Info
Emerging pathogen originally isolated in Asia Antifungal resistance is common Easily transmissible from person to person
32
Candida auris first isolation
Ear canal of patient in Japan
33
Trichosporon species
Two of interest: 1) T. beiglii 2) T. capitatum
34
Trichosporon Colony Morphology
Yeastlike At first cream colored, moist, soft Later finely wrinkled, heaped, and darkens to yellowish-grey
35
Trichosporon species Microscopic
3 days - true hyphae and pseudohyphae with blastoconidia singly or in short chains. Arthroconidia form on older cultures
36
Trichosporon species Pathogenicity
T. beiglii causes white piedra Occurs almost exclusively in immunocompromised patients
37
Trichosporon species Germ tube
Negative
38
Trichosporon species Urease test
Positive
39
Geotrichum candidum Colony Morphology
Young colonies: white, yeast-like Mature colonies: Submerged hypae at periphery giving ground glass appearance Most strains do NOT grow at 37 C
40
Geotrichum candidum Microscopic
3 days - true hyphae form that segment into rectangular arthroconidia, varying in size NO blastoconidia along hyphae NO alternating of light/dark
41
Geotrichum candidum Pathogenicity
Causes geotrichosis - rare infection that may produce lesions in the mouth, intestines, and lungs Cause disease mostly in immunocompromised hosts
42
Cryptococcus neoformans General Info
Widely distributed in soil mixed with excreta from poultry Common infection in AIDS population
43
Cryptococcus neoformans Colony Morphology
Begins as smooth white to tan colony, may become mucoid Cream to brown with age "Stringy" when trying to remove colony
44
Cryptococcus neoformans Microscopic
No pseudohyphae, Irregular sized, spherical, thick-walled yeast cells with spaces between them
45
Cryptococcus neoformans Urease
Positive
46
Cryptococcus neoformans Nitrate
Positive
47
Cryptococcus neoformans India Ink
Positive for capsule
48
Cryptococcus neoformans Niger Seed Agar
Positive Detects phenol oxidase production of yeast resulting in production of melanin Red-brown pigment
49
Cryptococcus neoformans Pathogenicity
Cryptococcosis Subacute or chronic infection most frequently involving CNS (meningitis) AIDS patients
50
Cryptococcus albidus General Info
Common transient on human skin and has been reported as rare cause of pulmonary, CNS, and vaginal infections
51
Cryptococcus albidus Colony Morphology
Cream colored Smooth to mucoid Yeast-like
52
Cryptococcus albidus Microscope
SAB - demonstrates globose to avoid budding yeast-like cells or blastoconidia
53
Cryptococcus albidus India Ink
Positive
54
Cryptococcus albidus Urease
Positive
55
Cryptococcus laurentii General Info
Rare cause of pulmonary and cutaneous infection and continuous ambulatory peritoneal dialysis (CAPD)
56
Cryptococcus laurentii Colony Morphology
Cream colored, sometimes a deeper orange-yellow with age Smooth mucoid texture
57
Cryptococcus laurentii Microscopic
SAB - produces spherical and elongated budding yeast-like cells or blastoconidia
58
Cryptococcys laurentii India Ink
Positive
59
Cryptococcus laurentii Urease
Positive
60
Candida glabrata Colony Morphology
Small yeast-like colonies Pasty, smooth White to cream
61
Candida glabrata Microscopic
CM 3 days - demonstrates only small, round to oval, single terminal budding Nonencapsulated yeast cells, tend to form compact clusters No pseudohyphae
62
Candida glabrata
Assimilates only glucose and trehalose
63
Candida glabrata Pathogenicity
Causes torulopsosis Infection occurring usually in blood stream or UTI, sometimes in the lungs
64
Rhodotorula species Colony Morphology
Pink to coral Yeast-like Soft and smooth
65
Rhodotorula species Microscopic
CM 3 days - demonstrates budding round or oval cells variable in size with rare rudimentary pseudohyphae No ascospores
66
Rhodotorula species Urease
Positive
67
Rhodotorula species Pathogenicity
Associated with contaminated equipment such as catheters, contaminated IV solutions and brochioscopes Infections are present in terminal stages of debilitating disease
68
Saccharomyces species Colony Morphology
Smooth, moist White to cream colored
69
Saccharomyces species Microscopic
CM 3 days - demonstrates yeast cells of various shapes with multilateral budding Few very short pseudohyphae
70
Saccharomyces species Kinyoun stain
Characteristic ascospores seen when stained with Kinyoun and grown on special media
71
Saccharomyces species Pathogenicity
Usually nonpathogenic Has been implicated in various infections in predisposed individuals
72
Prototheca wicherhamii Colony Morphology
Soft, wet yeastlike White to light tan colonies
73
Prototheca wicherhamii Microscopic
Large non-budding cells with a symmetrical morula-like structure Organism resembles algae Chlorella
74
Prototheca wicherhamii Pathogenicity
Previously thought to be a skin saprophyte Now identified as rare opportunistic pathogen
75
Malssezia furfur General Info
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
Malassezia furfur Colony Morphology
Organism will grow in yeast form only when media has been overlaid with 1-2 ml of olive oil
77
Malassezia furfur Microscopic
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
Germ Tube Positive Organisms
Candida ablicans Candida dubliensis - some strains, not all
79
Trichosporon species
Hyphae present Arthroconidia positive Urease positive
80
Candida species
Hyphae present Blastoconidia positive
81
Cryptococcus species
Hyphae not present Urease positive Inositol assimilation Nitrate positive
82
Rhodotorula species
Hyphae not present Urease positive Inositol negative
83
Candida glabrata
Hyphae not present Urease negative Small cells on Cornmeal Dextrose positive Trehalose positive

Mycology (9 decks)

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