LESSON 4: LABORATORY METHODS FOR ISOLATION AND IDENTIFICATION OF MEDICALLY IMPORTANT YEAST

Question 1

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

Answer 1

Yeast

Question 2

Cell wall of yeast: ___________

Answer 2

Chitin; also Glucans and Mannans

Question 3

Cell membrane of yeast: _____________

Answer 3

Ergosterol

Question 4

• Primary isolation medium for yeast

Answer 4

a. Sabouraud Dextrose Agar (SDA)

Question 5

• Acidic pH (5.0) inhibits growth of
  bacteria

Answer 5

a. Sabouraud Dextrose Agar (SDA)

Question 6

• High concentration of sugar

Answer 6

a. Sabouraud Dextrose Agar (SDA)

Question 7

inihibits bacteria

Answer 7

Chloramphenicol

Question 8

inhibits saprobes

Answer 8

Cycloheximide

Question 9

• Selective medium for isolation of fungi

Answer 9

b. Mycosel Agar (SDA with Chloramphenicol and
Cycloheximide)

Question 10

• Screening test used to differentiate
  Candida albicans and Candida dubliniensis from
  other yeast

Answer 10

Germ Tube

Question 11

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

Answer 11

Germ tube

Question 12

• Corn meal with Tween 80 Agar Test

Answer 12

Morphology Studies (Dalmau Plate Method)

Question 13

For distinguishing various species
Candida spp. and other yeasts

Answer 13

Morphology Studies (Dalmau Plate Method)

Question 14

is added to
cornmeal agar to reduce the surface tension to allow for the development of pseuodhyphal,
hyphal, blastoconidial growth, chlamydospores,
and arthroconidia

Answer 14

Polysorbate (Tween) 80

Question 15

Used in the identification of different
yeasts

Answer 15

Urease Test

Question 16

Same as used in bacteriology

Answer 16

Urease Test

Question 17

urease test color when positive

Answer 17

intense pink color

Question 18

urease test color when negative

Answer 18

no color change

Question 19

Determines the ability of a yeast isolate
to use a particular carbohydrate substrate as its
sole carbon in a medium

Answer 19

Carbohydrate Assimilation Test (CAT)

Question 20

• For precise identification of frequently
  encountered yeasts

Answer 20

Carbohydrate Assimilation Test (CAT)

Question 21

• Identification is obtained through
  Analytical Profile Index or using Identification
  Software

Answer 21

Carbohydrate Assimilation Test (CAT)

Question 22

• Composed of 20 cupules for 19
  assimilation tests

Answer 22

API 20°C AUX

Question 23

are inoculated with semisolid minimal medium

Answer 23

cupules

Question 24

___________ will grow if they are capable of
utilizing each substrate as the sole carbon source

Answer 24

yeast

Question 25

Reactions are read by comparing to growth control

Answer 25

API 20°C AUX

Question 26

Test use for API 20 degrees C AUX

Answer 26

Carbohydrate Assimilation Test

Question 27

Incubations of API 20°C AUX

Answer 27

29°C ± 2°C for 48-72 hours

Question 28

Limitations for API 20°C AUX

Answer 28

Intended uniquely for ID of yeast including in its database (44 species)

Question 29

- Determines the ability of a yeast to degrade a specific carbohydrate

Answer 29

Carbohydrate Fermentation Test (CFT)

Question 30

- ___________is demonstrated by production of gas

Answer 30

Fermentation

Question 31

- Useful when other tests fail to identify the isolate

Answer 31

Carbohydrate Fermentation Test (CFT

Question 32

Carbohydrate Fermentation test positive color

Answer 32

Green

Question 33

Carbohydrate Fermentation test negative color

Answer 33

yellow

Question 34

- Used for isolation and differentiation of clinically significant Candida spp.

Answer 34

Chromogenic Agar

Question 35

-__________, ________, ________ produce different colors

Answer 35

Colonies of C. albicans, C. tropicalis, and C. krusei

Question 36

CGB means

Answer 36

L-Canavanine, Glycine, Bromothymol Blue

Question 37

Used for the differentiation of: - Cryptococcus gattii vs Cryptococcus neoformans

Answer 37

CBG