Microbiology Lab Quiz 03/21

Front 1

What is hemolysin?

Back 1

A hemolysin is a gram positive cocci that produce exotoxins. The exotoxins that it produces have the ability to destroy red blood cells and hemoglobin.

Front 2

Hemolysin produces exotoxins, what do the exotoxins do?

Back 2

Exotoxins have the ability to destroy red blood cells and hemoglobin.

Front 3

What 3 genera of bacteria produces hemolysin?

Hint: think alphabet

Back 3

1. B-hemolysis

2. A-hemolysis

3. Y-hemolysis

Front 4

Name the 3 categories of hemolysin and what genera they are produced from.

Back 4

1. Streptococcus pyogenes - made by B-hemolysis

2. Streptococcus pneumoniae - made by A-hemolysis

3. Staphylococcus epidermis - made by Y-hemolysis

Front 5

How does Streptococcus pyogenes look like on agar?

Back 5

Some growth appears but the area that surrounds it is clear. The area around it is clear because red blood cells are completely destroyed.

Front 6

What does Streptococcus pneumoniae look like on an agar plate?

Back 6

Green areas appear around the colonies. They appear green because the red blood cells are partially destroyed.

Front 7

What does Staphylococcus epidermis look like on an agar plate?

Back 7

No hemolysis is shown so it appears as ordinary growth and no changes to agar.

Front 8

What is Catalase?

Back 8

It's an enzyme that contains aorobes, microaerophiles, and faculative anaerobes which convertes hydrogen peroxide to water and oxygen gas.

Front 9

Catalase can convert hydrogen peroxide into: ______________

Back 9

Water and oxygen gas.

Front 10

What does the chemical reaction formula of Catalase look like?

Back 10

2H2O2 ---Catalase----> 2H20 + O2(g)

Front 11

How can we tell is a test for catalase production is positive?

Back 11

We have to add hydrogen oxide. If oxygen gas bubbles form immediately after adding hydrogen peroxide, it means the culture is positive for catalase production.

Front 12

The catalase test is used to distinguish between what two genera of Gram positive cocci?

Back 12

It is used to distinguish between Micrococcaceae which is catalase positive and Streptococcaceae which is catalase negative.

Front 13

The coagulase test is used to distinguish between this pathogen and Gram-positive cocci...

Back 13

Staphylococcus aureus

Front 14

Name the medium that will be used to perform the coagulase test during the lab.

Back 14

Rabbit plasma that has been treated with anticoagulant.

Front 15

What indicates a test for coagulase production is positive when performing slide test?

Back 15

Bacteria is transferred to a slide that contains a small amount of plasma. Agglutination of the cells occur on the slide within the next 2 minutes if the test organism is positive for coagulase production.

Front 16

What indicates a test for coagulase production is positive when performing tube test?

Back 16

You can tell if an organism is positive for coagulase production when you add the test organism in a test tube then add rabbit plasma. If the plasma begins to coagulate within the next 24 hours it means the test organism is positive for coagulase production. You will also see fibrin threads form and thicken if the test organism is positive.

Front 17

What reaction turns the nutrient phenol red broth into dark pink color (when pH becomes alkalinic)?

Back 17

Deanimation of peptone amino acids which produces ammonia.

Front 18

What reaction turns the nutrient phenol red broth into yellow color (when pH becomes acidic)?

Back 18

Carbohydrates ferment which produces acid.

Front 19

What is the function of a Durham tube in this test?

Back 19

The Durham test is used to tell the difference between members of Entero-bacteriaceae from other Gram negative rods.

Front 20

What does it mean if your blood agar plate has clearing around the bacterial growth?

Back 20

It means the blood agar plate has an exotosin called hemolysins which can destroy red blood cells and hemoglobin. One example of a hemolysin is Streptococcus pyogenes.

Front 21

What does it mean if your phenol red tube with glucose turned yellow?

Back 21

It means the pH level is below 6.8 due to acid production. Acid is produced from fermentation of the glucose in the phenol red tube.

Front 22

What is the purpose of phenol red carbohydrate broth?

Back 22

It's purpose is to differentiate members of Enterobacteriaceae family. It is also used to tell the difference between Enterobacteriaceae from other gram negative rods.

Front 23

What effect does b-hemolysis have on red blood cells? And what does it look like on a blood agar plate?

Back 23

Completely destroys red blood cells and hemoglobin. This results in a clearing around growth on the blood agar plate.

Front 24

What effect does a-hemolysis have on red blood cells? And what does it look like on a blood agar plate?

Back 24

Red blood cells and hemoglobin are partially destroyed which gives a greenish color on blood agar plate.

Front 25

What effect does y-hemolysis have on red blood cells? And what does it look like on a blood agar plate?

Back 25

No hemolysis and no change to the blood agar plate.

Front 26

What is the purpose of the Catalase test?

Back 26

To detect the ability of a Gram-positive, catalase-positive coccus to clot plasma.

Front 27

What specific bacteria can the Catalase test differentiate? (tell the difference?)

Back 27

Can tell the difference between Staphylococus aureus and or Micrococcaceae.

Front 28

What effect does Catalase have on hydrogen peroxide?

Back 28

Can break down hydrogen peroxide down into water and oxygen gas.

Front 29

How does bacteria produce hydrogen peroxide? And which type of bacteria produce it?

Back 29

Bacteria that are aerobic and faculatively anaerobic can produce hydrogen peroxide by non-enzymatic transfer of electrons from reduced flavoprotein to oxygen.

Front 30

What is the purspose of the Coagulase Test?

Back 30

Used to differentiate Staphylococcus aureus from other gram-positive cocci.

Front 31

What is coagulase?

Back 31

An enzyme that forms a protective fibrin barrier around bacterial cells to shield from phagocytosis.

Front 32

What is the purpose of the Fermentation test?

Back 32

Used to detect the ability of an organism to ferment various carbohydrates.

Front 33

What else can the Fermentation test be used for? Hint: think detection.

Back 33

Can be used to identify Gram-negative enteric bacteria.

Front 34

What is fermentation?

Back 34

Fermentation is a metabolic process in which the final electron acceptor is and organic molecule.

Front 35

What color does phenol red turn into when the pH is below 6.8?

Back 35

It turns yellow.

Front 36

What color does phenol red turn into when the pH is above 7.4?

Back 36

Pink to magenta.

Front 37

What does it mean when phenol red goes below pH 6.8?

Back 37

Acid production from fermentation of carbohydrates.

Front 38

What does it mean when phenol red goes above pH of 7.4?

Back 38

Deamination of peptone amino acids.

Front 39

Besides phenol red, what other else can be used to test pH?

Back 39

Bromcresol.

Front 40

What else can bacteria ferment?

Back 40

Some bacteria can convert other sugars into glucose.