Lab Quiz

Question 0

What is the goal of differential media

Answer 0

It will aid in the identification of unknown gram negative rods in the Enterobacteriaceae family

Question 1

Enzymatic activity of bacteria can be observed by using what?

Answer 1

Differential media

Question 2

Enterobacteriaceae family include

Answer 2

Normal gastrointestinal microbiota, opportunists, and pathogens.

Question 3

Infections cause by enterics include

Answer 3

Sepsis and meningitis

Question 4

Types of standard differential tube media:

Answer 4

• Simmon’s Citrate Agar (SCA)
• Urea agar
• Sulfide-Indole-Mobility (SIM) medium
• Triple Sugar Iron ( TSI)

Question 5

SIM media

Answer 5

Is a combined media that tests for motility, sulfur reduction to hydrogen sulfide H2S

Question 6

H2S production in SIM:

What does the SIM media contains? What color is it turn when combined to H2S?

Answer 6

SIM contains ferrous sulfate ( iron salt)

That turn black when combine to H2S gas

Question 7

Motility in SIM:

When are bacteria motile? Non motile?

Answer 7

If the bacteria swim away from the line of inoculation (stab), they are motile.
If the bacteria grow only along the stab line, they are non motile.

Question 8

What is tryptophanase?

Answer 8

It is an enzyme produce by some bacteria.

Question 9

What does tryptophanase do?

Answer 9

Are able to hydrolyze the amino acid tryptophan producing Indole and pyruvate.

Question 10

Simmon’s Citrate is used to

Answer 10

Differential gram negative bacteria on the basis of citric acid utilization.

Question 11

What does agar medium contains?

Answer 11

Sodium citrate as the only available carbon source.

Question 12

What indicator the medium agar contain

Answer 12

Bromthymol blue, which is green at pH 6.9 and blue at pH 7.6

Question 13

Organisms which have the enzyme citrase, are able of what?

Answer 13

They are able to to utilize the sodium citrate and nitrogen sources and produce ammonia.
Convert the agar to alkaline pH and a blue color

Question 14

Triple Sugar Agar contains how many carbohydrates?
The medium contain what?
What indicator? Color?

Answer 14

• Three carbohydrates : glucose, sucrose and lactose.
• Peptones as a carbon and nitrogen source
• phenol red ( is yellow in acidic pH and pink red I. Alkaline pH).

Question 15

Peptonization

Answer 15

It is when peptones ( amino acid) are used for food, ammonia is produced

Question 16

Urea hydrolysis:
Urease?
Urea agar contains?
When urease positive bacteria are inoculated, medium do what?

Answer 16

• It is an enzyme which hydrolyze a certain amino acids and urea to ammonia and carbon dioxide.
• urea, peptones, glucose and phenol red.
• medium becomes alkaline turning the phenol red indicator bright pink.

Question 17

&beta galactosidase enzyme causes the release of what?& glucosidase enzyme? Tryptophan deaminase enzyme?

Answer 17

• release of a dye turning the colonies pink.
• turn colonies to blue.
• turn the media to beige brown

Question 18

What is a smear? Its Role?

Why do you the heating treatment?

Answer 18

• It is the application of the bacteria to a slide for purpose of staining.
• so the cells are not piled on top of each other.
• to kill the bacteria and stick them to the plate.

Question 19

Time for gram stain:

• Crystal violet, let stand for?
• Hold the slide at what angle to wash w/c water?
• wash w/c water for?
• Gram ‘s iodine?
• Gram’s alcohol for?
• Safranin for?

Answer 19

• 30 sec
• 45 degree
• 2 sec
• 1 min
• 5 to 10 sec
• 45sec