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Myco > Yeast > Flashcards

Yeast Flashcards

Midterm

1
Q

it is the main factor why yeasts have been prevalent

A

immunosuppression

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2
Q

infections caused by yeasts may be — and —

A

extremely aggressive and difficult to treat

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3
Q

t or f: yeast is often part of the human microbiota

A

true

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4
Q

yeasts can be classified into

A

yeast (mostly asexually but able reproduce sexually) and yeast-like (not capable of sexual reproduction)

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5
Q

generally, yeasts can reproduce asexually through —, but they can also reproduce sexually through —

A

asexually= blastoconidia (budding); sexually= ascopores and basidiospores

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6
Q

give the general characteristics of yeast

A

eukaryotic, unicellular, round-oval, 2-60um, reproduce asexually (blastoconidia)

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7
Q

what are the characteristics for differentiation of yeasts

A

cell size, presence and absence of capsule, budding phase (broad, narrow)

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8
Q

diiferentiation of yeast in — and — is ften impossible

A

direct microscopy and histopathologic examination

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9
Q

an outpouching of the cell wall that becomes tubular and does not have a constriction at its base

A

germ tube

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10
Q

it represents the initial stage of true hyphae formation

A

germ tube

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11
Q

buds elongate, fail to dissociate, and form subsequent buds

A

pseudohyphae

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12
Q

resemble links of sausage

A

pseudohypahe

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13
Q

have cell wall constrictions rather than true intracellular septation delineating the fungal cell borders

A

pseudohyphae

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14
Q

macroscopic appearance of yeasts

A
  • moist
  • creamy
  • may have brght pigments
  • either hyaline/melanized (phaeiod)
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15
Q

t or f: some yeasts may produce a capsule resulting in a shiny or mucoid colonial appearance

A

true

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16
Q

this is responsible for most commonly encountered opportunistic fungal infection

A

candida spp

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17
Q

candida spp is the — most common cause of hospital acquired bloodstream infection (BSI)

A

4th most common

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18
Q

mortality rate of candida spp

A

as high as 50%

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19
Q

this is the most commonly isolated yeast

A

Candida albicans which causes candidiasis

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20
Q

what are the symptoms/clinical manifestations of candidiasis

A

oroesophageal candidiasis, intertriginous candidiasis, paronychia, onychomycosis, vulvovaginitis, thrush

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21
Q

what specific clinical manifestation of candidiasis: skin folds are involved

A

intertriginous candidiasis

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22
Q

what specific clinical manifestation of candidiasis: involves tissues surrounding the nails

A

paronychia

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23
Q

what specific clinical manifestation of candidiasis: affects nail and nail beds

A

onychomycosis

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24
Q

what specific clinical manifestation of candidiasis: fish eye

A

vulvovaginitis

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25
Q

what specific clinical manifestation of candidiasis: an infection of the mucous membranes in the mouth, and is considered a localized infection

A

thrush

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26
Q

what specific clinical manifestation of candidiasis: can be seen in newborns, patients with HIV, and diabetes

A

thrush

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27
Q

thrush is infection of candida albicans in what areas

A

mouth

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28
Q

t or f: thrush caused by candida albicans is a localized infection

A

true

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29
Q

thrush can be seen in what patients

A

newborns, HIV, diabetes

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30
Q

enumerate the non-albicans candida

A

C. glabrata and C. parapsilosis

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31
Q

these are once believed to not cause diseases

A

non-albicans candida

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32
Q

t or f: non-albicans candida was once believed to not cause disease

A

true

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33
Q

it is a common urinary isolate candida

A

C. glabrata

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34
Q

C. glabrata can be differentiated with C. albicans through

A

sugar (trehalose) assimilation

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35
Q

this candida is resistant to antifungal drugs

A

C. glabrata

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36
Q

infections caused by C. glabrata can cause

A

endocarditis and meningitis

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37
Q

C. glabrata is higher in what population

A

higher in older adults than in young adults and children

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38
Q

this candida is seen in neonates

A

C. parapsilosis

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39
Q

this candida is the 2nd most common cause of positive blood culture

A

C. parapsilosis

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40
Q

what candida is positive for germ tube

A

C. albicans

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41
Q

laboratory diagnosis of Candida

A

Microscopic appearance and testing for germ tube (only albicans is +)

42
Q

t or f: in microscopic appearance of candida reveals budding cells

A

true

43
Q

diameter of candida in microscopy

A

2-4um

44
Q

in microscopic appearance of candida — shows regular points of constrictions

A

pseudohyphae

45
Q

what candida demonstrates true septate hyphae

A

C. albicans

46
Q

this candida have a smaller blastoconidia at 1-4um

A

C. glabrata

47
Q

t or f: yeasts are hard to treat because they are hard to distinguish from each other

A

true

48
Q

how to do germ tube

A

add yeast colony to 0.5mL serum

49
Q

possible samples for yeast determination

A
  • vaginal discharge
  • urine
  • sputum
  • stool
  • wound discharges (oberved through gram stain)
  • blood culture
50
Q

what part of the body is vulvovaginitis be observed

A

vaginal canal up to cervix (causes bad odor)

51
Q

thrush is very evident in what part of the body

A

tongue

52
Q

this is one of the diagnostic testing done to do to differentiate yeasts

A

temperature

53
Q

this causes meningitis, pulmonary disease, and septicemia

A

cryptococcus spp

54
Q

these are the most common routine tests done to identify yeasts

A

germ tube and india ink

55
Q

it is the major cause of opportunisitc infections in people with AIDS

A

cryptococcus

56
Q

cryptococcus is commonly found in

A

soil contaminated with pigeon droppings

57
Q

cryptococcus most common specimen

A

CSF (most routine for india ink testing)

58
Q

cryptococcus can be acquired through

A

inhalation

59
Q

this is the mst notable pathogen of the cryptococcus spp

A

C. neoformans

60
Q

this protects the cryptococcus from dry condition

A

polysaccharide capsules

61
Q

the main way of identifying C. neoformans using india ink using microscopy

A

capsulated budding yeast

62
Q

t or f: cryptococcus loves dry conditions

A

false, they prefer mucoid/wetter environment

63
Q

the most widely used and easiest method to test cryptococcus

A

india ink

64
Q

this testing method is able to delineate the large capsule of cryptococcus spp due to the inability of the ink to penetrate the capsule

A

india ink

65
Q

ratio of sample and india ink

A

1 drop sample (CSF):1 drop india ink

66
Q

disadvantage of india ink

A

less sensitive

67
Q

this is an immunoassay type of testing for cryptococcus

A

cryptococcal antigen detection (CAD)

68
Q

t or f: india ink is more sensitive than cryptococcal antigen detection (CAD)

A

false, CAD is more sensitive

69
Q

can be misidentified as positive for india ink

A

bubbles, WBCs

70
Q

t or f: clear capsule/halo of capsule indicates bubbles or WBCs

A

false, clear halo means it is true positive for india ink

71
Q

t or f: C. neoformans can only have single budding

A

false, it can have single or multiple budding

72
Q

shape of C. neoformans

A

spherical

73
Q

describe the wall of C. neoformans

A

thick-walled (due to capsule)

74
Q

size of C. neoformans

A

2-15 um in diameter

75
Q

t or f: polysaccharide capsule is true for all cryptococcus spp

A

false, it is true to most isolates but not all

76
Q

this is an opportunistic, atypical fungus

A

pneumocystis

77
Q

pneumocystis can be acquired

A

in early life

78
Q

t or f: pneumocystis infection is asymptomatic for immunocompetent individuals

A

true

79
Q

this yeast is first considered as a protozoan

A

pneumocystis

80
Q

fun fact: pneumocystis is classified as yeast instead of protozoan (parasite) after what test

A

DNA testing

81
Q

this pneumocystis is previously classified as protozoan and is commonly found in rats

A

P. carinii

82
Q

this pneumocystis is often recovered from humans

A

P. jirovecii

83
Q

other tests for the identification of yeasts

A
  • carbohydrate assimilation
  • chromogenic substrates (CHROMagar)
  • cornmeal agar
  • potassium nitrate assimilation (KNO3)
  • Urease
84
Q

t or f: EIA can be used for yeast identification

A

true, but are not readily available, rigorous, and expensive so its not routinely used

85
Q

this is also called sugar fermentation test

A

carbohydrate assimilation

86
Q

this test is used to identify which carbohydrates a yeast can use aerobically as a sole carbon source

A

carbohydrate assimilation

87
Q

what are observed or the indications in sugar fermentation (carbohydrate assimilation) test

A

turbidity, change in color, indicators

88
Q

this test can be used to differentiate species of candida

A

chromogenic substrates (CHROMagar cacndida)

89
Q

this is a differential type of media, especially in candida spp (you can observe the different colonial growth patterns)

A

CHROMagar candida

90
Q

this presumptively identifies C albicans, C tropicalis, and about 10 other candida spp

A

CHROMagar candida

91
Q

t or f: if you get colonies from CHROMagar, it reveals their true morphologic characteristics microscopically

A

true

92
Q

this allows the identification of morphology of yeasts, not just that of candida

A

cornmeal agar

93
Q

what morphologies can you observe from colonies of cornmeal agar

A
  • blastoconidia
  • chlamydoconidia
  • pseudohyphae
  • arthroconidia
94
Q

this determines the ability of yeasts to use nitrates as the sole source of nitrogen

A

potassium nitrate assimilation (KNO3)

95
Q

what yeast is the positive control for KNO3

A

Cryptococcus albidus

96
Q

what is the negative control for KNO3

A

Candida albicans

97
Q

this is used for the detection of isolates producing the enzyme urease through christensen urea agar

A

urease

98
Q

what agar is used for urease test

A

Christensen urea agar

99
Q

this clinically significant yeast is negative for urease

A

Candida spp

100
Q

t or f: most Cryptococcus are negative for urease

A

false, they are mostly positive

101
Q

what indicator is observed if urease test is positive

A

there will be a change in color of the media

Myco (5 decks)

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