3/27/24

Question 1

Urea Hydrolysis Test

Answer 1

used to differentiate rapid urease positive bacteria from slower urease-positive and urease-negative bacteria

Question 2

Urea definition

Answer 2

a product of decarboxylation of some amino acids, and is the primary nitrogenous waste in urine of many land animals

Question 3

Urease enzyme

Answer 3

catalyzes the hydrolysis of urea to ammonia and carbon dioxide (NH3 and CO2)

Question 4

Urea Hydrolysis Agar contains: indicator

Answer 4

Phenyl red indicator
Potassium phosphate ( pH buffer)
Urea

Question 5

Urea Hydrolysis Results

Answer 5

• Urea hydrolysis to ammonia will raise the pH and turn the tubes pink ( positive)
• Within 24 hours = rapid urea hydrolysis
• Between 24 hours – 6 days = weak urea hydrolysis

Question 6

SIM Medium stands for:

Answer 6

A combination medium used for the determination of three activities:
* Sulfur reduction
* Indole production from tryptophan
* Motility

Question 7

What kind of medium is sims and what does it contain

Answer 7

semisolid medium that contains:
* Casein and animal tissue as sources of amino acids
* Iron-containing compound (ferrous ammonium sulfate)
* Sulfur (sodium thiosulfate)
* Agar

Question 8

SIMS test reaction:

Answer 8

Sulfur reduction to H2S (hydrogen sulfide)
* can happen in 2 different ways depending on the enzymes present

Question 9

Sulfur reduction to H2S (hydrogen sulfide) can happen in 2 different
ways depending on the enzymes present:

Answer 9

*Cysteine desulfurase catalyzes the hydrolysis of the sulfur
containing amino acid cysteine to pyruvate and H2S during
putrefaction
*Thiosulfate reductase catalyzes the reduction of sulfur (in the form
of thiosulfate) to H2S at the end of an anaerobic respiratory
electron transport chain

Question 10

SIMS if tryptophanase is present

Answer 10

If tryptophanase is present, indole will be produced from tryptophan
-The presence of indole can then be detected by addition of Kovac’s
reagent

Question 11

SIMS if sulfur is reduced

Answer 11

H2S will react with iron to form ferric sulfide (FeS), a black precipitate
-If indole is produced from tryptophan, addition of Kovac’s reagent will produce a red color

Question 12

Triple Sugar Iron Agar contains:

Answer 12

Digests of casein and animal tissues (sources of carbon and nitrogen)
* Ferrous sulfate
Substrates:
* Glucose
* Lactose
* Sucrose
* Phenol red (pH indicator)

Question 13

TSIA can differentiate

Answer 13

between bacteria on the basis of glucose fermentation,
lactose fermentation, sucrose fermentation, and sulfur reduction

Question 14

Shallow agar slant (aerobic) with a deep butt (anaerobic)

Answer 14

Inoculation is performed by a stab in the agar butt and then a fishtail streak of the slant (TSIA)

Question 15

Glucose-only fermenters TSIA

Answer 15

Acid products lower the pH and turn the entire medium yellow within a few hours
Will appear as a red slant with a yellow butt after 24
hours

Question 16

Glucose and lactose and/or sucrose fermenters TSIA

Answer 16

Acid products lower the pH and turn the entire medium yellow within a few hours
- will appear completely yellow after 24 hrs
- May also have gas production indicated by fissures in the medium or a lifting of the agar in the tube

Question 17

Hydrogen sulfide (H2S) production TSIA

Answer 17

Black precipitate: If the black precipitate obscures the butt, the color of the slant determines which carbohydrates have been fermented
* Red slant – glucose fermentation
* Yellow slant – glucose and lactose/sucrose fermentation

Question 18

(TSIA) Utilization of peptone/amino acids ( without fermenting any available carbohydrates)

Answer 18

products that turn the medium red
- Organisms that can use peptone aerobically and anaerobically will turn both the slant and butt red
- Obligate aerobes will turn only the slant red (can be difficult to differentiate, compared to uninoculated control)

Question 19

Blood Agar Test contains

Answer 19

Contain 5% blood (sheep blood in this case) in a tryptic
soy agar base (undefined)

Question 20

Three types of hemolysis ( Blood Agar Test)

Answer 20

β-hemolysis, α-hemolysis, γ-hemolysis

Question 21

α-hemolysis

Answer 21

partial destruction of RBCs which results in a greenish discoloration of the agar around the colonies

Question 22

β-hemolysis

Answer 22

complete destruction of RBCs and hemoglobin which results in a clearing of the medium around the colonies

Question 23

γ-hemolysis

Answer 23

non-hemolysis (simple growth with no change to the medium)