Biochemical Tests

Question 1

What are the ingredients in TSI agar

Answer 1

Glucose
Lactose
Sucrose

(Lactose and sucrose 10x greater concentration)

Question 2

What is the principle behind TSI agar?

Answer 2

Glucose fermenter will acidify media (yellow)

If organism can ferment lactose/sucrose will stay acidic (yellow)

Nonfermenter= use protein and neutralize slant (red)

K/A - glucose only
A/A - sucrose/lactose
K/K - no glucose/lactose

Question 3

What ingredient is in the indole test?

Answer 3

Tryptophan

Question 4

principle of the indole test and color of reaction

Answer 4

Detect tryptophanase

Organism ability to convert tryptophan to indole

Red = positive 
Yellow = negative

Question 5

What are the ingredients in methyl red?

Answer 5

PH indicator

Red = < 4.4

Question 6

principle of the methyl red test and reaction colors

Answer 6

End products of glucose fermentation

Mixed acid = Red (positive)

Question 7

What are the ingredients in vogues proskauer?

Answer 7

40% KOH with acetoin

Intensified with alpha-naphthol

Question 8

What is the principle of the vogues proskauer test?

Answer 8

End products of glucose fermentation

Acetoin (neutral) (red)

Question 9

What are the ingredients in the nitrate test?

Answer 9

Nitrate broth 
Reagent A (alpha-naphthylamine)
Reagent B (sulfanilic acid)

Question 10

What is the principle of the nitrate test and color of reactions

Answer 10

Bacteria ability to reduce nitrate to nitrite

Red = positive
Colorless- add zinc dust
PINK AFTER ZINC = negative

Question 11

What is the principle of the lysine iron agar test and colors of reactions

Answer 11

Organism ability to decarboxylate or deaminate lysine

Positive decarboxylation: purple/purple
Positive deamination: red slant

Negative: yellow

Question 12

What is the principle of the urease test and color of reaction

Answer 12

Hydrolysis urea to CO2 and ammonia increase pH

Positive bright pink
Negative: no change

Question 13

What is the principle of the citrate test and color of reaction

Answer 13

Lactose fermenting bacteria
Of organism can only use citrate as carbon source

Blue positive
Green negative

Question 14

What is the principle of LDC, ODC, ADC? Color of reaction?

Answer 14

Ability of organism to produce decarboxylase enzymes

Positive - red purple
Negative - yellow

Question 15

what type of coagulase is being tested for in the slide test?

Answer 15

bound

Question 16

what type of coagulase is being tested for in the tube test?

Answer 16

free

Question 17

what is the purpose of the modified oxidase test?

Answer 17

differentiate micrococcus from staphylococcus

Question 18

what is the principle of the modified oxidase test?

Answer 18

cytochrome oxidase oxidizes tetramethyl-p-phenylenediamine

Question 19

what is the purpose of the PYR test?

Answer 19

ability of organism to hydrolyze a substrate

diff enterococcus from streptococcus

Question 20

positive PYR

Answer 20

pink to red (enterococcus)

Question 21

negative PYR

Answer 21

no color change (strep)

Question 22

what is the purpose of the OF test?

Answer 22

determine if an organism can utilize carbohydrates oxidatively or fermentatively

Question 23

what is the purpose of the string test?

Answer 23

diff vibrio from aeromonas and plesiomonas

Question 24

what is the purpose of the porphyrin test?

Answer 24

detect the presence of enzymes that convert aminolevulinic acid to porphyrin

Question 25

what is the reagent in the catalase test?

Answer 25

3% H2O2

Question 26

what is the reagent in the coagulase test?

Answer 26

EDTA rabbit plasma

Question 27

what does the ONPG test detect?

Answer 27

B-d-galactosidase

Question 28

what color is a positive citrate?

Answer 28

blue

Question 29

what color does LIA turn for lysine deaminase?

Answer 29

red

Question 30

what color is a positive LIA?

Answer 30

purple

Question 31

what is the reagent in the indole test?

Answer 31

Kovac's (p-dimethylaminobenzaldehyde)

Question 32

CAMP test principle

Answer 32

produce extracellular protein that enhances hemolysis of beta hemolytic s. aureus on SBA

Question 33

bile solubility principle

Answer 33

bile salts cause lysis of some organisms

Question 34

bile esculin principle

Answer 34

organisms can grow in 40% bile and produce esculinase hydrolyse esculin = black precipitate

Question 35

Positive oxidase color

Answer 35

Blue / purple

Question 36

What does pink after zinc mean?

Answer 36

Presence of residual nitrates (negative)

Question 37

ONPG purpose

Answer 37

Test for slow lactose fermentation

Question 38

Positive ONPG color

Answer 38

Yellow

Question 39

ONPG is most useful when differentiating what?

Answer 39

Late lactose fermenters from nonfermenters Example: shigella and some strains of E. coli

Question 40

Decarboxylation of lysine, ornithine, and arginine creates?

Answer 40

Alkaline amines

Question 41

Ornithine decarboxylase amine product

Answer 41

Putrescine

Question 42

Lysine decarboxylase product

Answer 42

Cadaverine

Question 43

Arginine decarboxylase product

Answer 43

Citrulline then ornithine

Question 44

Confirmatory test for X factor requirement

Answer 44

ALA

Question 45

ALA purpose

Answer 45

Determines the ability of an organism to synthesize protoporphyrin intermediates to hemin

Question 46

OF peptone to carb concentration

Answer 46

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