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Myco Viro > Laboratory Methods For Isolation And Identification Of Medically Important Yeast > Flashcards

Laboratory Methods For Isolation And Identification Of Medically Important Yeast Flashcards

1
Q

Eukaryotic, unicellular fungi
Reproduces by budding
Moist to waxy colonies
Round to oval, or less often elongate or irregular in shape

A

Yeast

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2
Q

Yeast cell wall

A

Chitin, glucans and mannans

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3
Q

Yeast cell membrane

A

Ergosterol

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4
Q

CULTURE MEDIA FOR ISOLATION

❏Primary isolation medium for yeasts
❏Acidic pH (5.0) inhibits growth of bacteria
❏High concentration of sugar

A

❏Sabouraud Dextrose Agar (SDA)

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5
Q

Acidic pH of SDA that inhibits the grow of bacteria

A

5.0

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6
Q

Chloramphenicol

A

Inhibits bacteria

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7
Q

inhibits saprobes

A

Cycloheximide

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8
Q

CULTURE MEDIA FOR ISOLATION

❏Selective medium for isolation of fungi

A

❏Mycosel Agar
(SDA with Chloramphenicol and Cycloheximide)

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9
Q

Test to determine if isolated colony is bacteria or yeast
-1 drop of sterile saline/water glass slide

A

Wet mount (from colony)

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10
Q

Germ tube Positive

A

No constriction

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11
Q

Germ tube Negative

A

Constriction

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12
Q

• Screening test used to differentiate Candida albicans and Candida dubliniensis from other yeast.
• Tests the ability of the yeast to produce tube-like projections from a conidia or spore in human serum or fetal bovine serum after 2-3 hours of incubation at 37°C.
No constriction
Germ tube Positive

A

GERM TUBE

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13
Q

• Used in the identification of different yeasts • Same as used in bacteriology

A

Urease Test

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14
Q

Intense pink color (Urease Test)

A

Positive

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15
Q

No color change (Urease Test)

A

Negative

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16
Q

• Corn meal with tween 80 agar test
• For distinguishing various species of Candida and other
yeasts
• Polysorbate (tween) 80 is added to cornmeal agar to reduce the surface tension to allow for the development of pseudohyphal, hyphal, blastoconidial growth, chlamydospores and arthroconidia.

A

Morphology Studies (Dalmau Plate Method)

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17
Q

Morphology Studies (Dalmau Plate Method)

A

Cornmeal Agar, Potato Dextrose Agar, Rice extract agar

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18
Q

Can be found on the terminal end of the pseudohyphae

A

Chlamydospore

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19
Q

Seen on cornmeal agar

A

Presence of blastoconidia, pseudohyphae, and chlamydospores

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20
Q

Organism that has Presence of pseudohyphae, blastocondia

A

C. albicans
C. dubliniensis
C. krusei
C. parapsilosis
C. keyfr (pseudotropicalis)
C. tropicalis

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21
Q

Organism that has presence of pseudohyphae, blastocondia, Chlamydoconidia/ Chlamydospores

A

C. albicans
C. dubliniensis

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22
Q

Organism that has presence of arthroconidia, yeast cells only

A

C. (Torulopsis) glabrata
Cryptococcus spp.
Rhodotorula spp.

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23
Q

Organism that has presence of pseudohyphae and yeast cells only

A

Saccharomyces spp.

24
Q

Organism that has presence of pseudohyphae, arthroconidia

A

Trichosporon spp.

25
Q

Determines the ability of a yeast to degrade a specific carbohydrate
Fermentation is demonstrated by production of gas Useful when other tests fail to identify the isolate

A

Carbohydrate Fermentation Test

26
Q

• Determines the ability of a yeast isolate to use a particular carbohydrate substrate as its sole carbon in a medium
• For precise identification of frequently encountered yeasts
• Identification is obtained through Analytical Profile Index or using Identification Software.

A

Carbohydrate Assimilation Test

27
Q

Carbohydrate Assimilation Test Identification is obtained through

A

Analytical Profile Index or using Identification Software.

28
Q

Principle:
• Composed of 20 cupules for 19 assimilation tests.
• The cupules are inoculated with semi-solid minimal medium.
• Yeast will only grow if they are capable of utilizing each substrate as the sole carbon source.
• Reactions are read by comparing to growth control

A

API 20 C AUX

29
Q

Carbohydate Assimilation Test
• API 20 C Interpretation if posotive

A

Will result to a turbid of the well

30
Q

Carbohydate Assimilation Test
• API 20 C Interpretation if negative

A

No turbid of the well

31
Q

Other ID Methods:
AUTOMATED IDENTIFICATION SYSTEM (Yeast)

A

Vitek 2 system
Microscan walkaway-96/40/ autoscan -4 systems
Phoenix system

32
Q

Incubation of Api 20 C Aux

A

29°C ± 2°C for 48-72 hours

33
Q

Positive color of Carbohydrate Fermentation Test

A

Yellow

34
Q

Negative color of Carbohydrate Fermentation Test

A

Green

35
Q

Used for isolation and differentiation of clinically significant Candida species
• Colonies of C. albicans,
C. tropicalis, and C. krusei produce different colors

A

Chromogenic Agars

36
Q

Color produce of C. albicans/ Candida dubliniernsis in Chromogenic Agars

A

Green

37
Q

Color of C. Tropicalis in chromogenic agars

A

Blue

38
Q

Color of C. Krusei in chromogenic agars

A

Purple

39
Q

Color of C. Glabrata in chromogenic agars

A

It varies (yellow, gold)

40
Q

CGB Agar Used for the differentiation of :

A

Cryptococcus gattii versus Cryptococcus neoformans

41
Q

CGB stands for

A

L-canavanine glycine bromthymol blue

42
Q

Positive reaction of CGB agar

A

Yellow green to cobalt blue

43
Q

Negative reaction of CGB agar

A

Yellow

44
Q

Identification test for C. albicans and C. dubliniensis

A

Germ tube

45
Q

Presumptive Identification Tests for Cryptococcus spp.,Rhodotorula spp., Trichosporon spp. (variable), C. krusei (variable), C. lipolytica

A

Rapid urease

46
Q

Presumptive Identification Tests for Cryptococcus species

A

India ink

47
Q

Other detection method

A

Serology

48
Q

Why use serology?

A

Ag and Ab are easier to detect vs growing the organism

49
Q

Ag and Ab are produced in large quantities and can be found in

A

Body fluids i.e. serum, CSF, urine

50
Q

Ab test:

A

Immunidiffusion
Radioallergosorbent Test RAST

51
Q

Ag test

A

Latex agglutination
Radioimmunoassay
Lateral flow

52
Q

Latex agglutination system

A

Anti-cryptococcal antibody-coated latex particles

53
Q

Lateral flow assay principle

A

Immunochromatographic dipstick assay

54
Q

Advantages of lateral flow assay

A
  1. No specimen pre treatment
  2. 2 years shelf life, room temp storage, condensed packaging
  3. Internal control line eliminates external conteol requirements
  4. As easy as home pregnancy test
  5. Only product fDA-cleared for both C. Neoformans and C. Gattii
55
Q

Lateral flow assay running time

A

10 mins

56
Q

Limitations of latex agglutination system

A

Cross reaction with trichosporon beigelii

57
Q

Latex agglutination system running time

A

45 mins

Myco Viro (11 decks)

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