Biochemical Reactions.

Question 1

When do we subject bacteria to biochemical reactions?

Answer 1

Once we have isolated the bacteria.

Question 2

What is the catalase test used for?

Answer 2

To differentiate between streptococci and staphylococci.

Question 3

Are streptococci catalase negative or positive?

Answer 3

Catalase negative.

Question 4

Are staphylococci catalase negative or positive?

Answer 4

Catalase positive.

Question 5

How do we carry out the catalase test?

Answer 5

We smear bacteria onto a slide and add hydrogen peroxide and observe what happens.

Question 6

During the catalase test, what indicates that a bacteria is catalase positive?

Answer 6

The sample starts to bubble.

Question 7

During the catalase test, what indicates that a bacteria is catalase negative?

Answer 7

There are no bubbles.

Question 8

What is the coagulase test used for?

Answer 8

To differentiate staphylococcus aureus from staphylococci.

Question 9

Are staph aureus coagulase positive or coagulase neagtive?

Answer 9

Coagulase positive.

Question 10

Are staphylococci coagulase positive or coagulase neagtive?

Answer 10

Coagulase negative.

Question 11

What is the function of coagulase?

Answer 11

It causes plasma to clot by converting fibrinogen to fibrin.

Question 12

What is the oxidase test used for?

Answer 12

To test for bacteria that produce cytochrome C.

Question 13

What is cytochrome C?

Answer 13

An enzyme in the electron transport chain.

Question 14

How can we identify bacteria that produce cytochrome C in the oxidase test?

Answer 14

Organisms that use this enzyme are oxidase positive and will turn the reagent blue or purple.

Question 15

What does a motility test help us to determine?

Answer 15

Whether our unknown organism can move.

Question 16

What happens if we place a gram negative bacterial cell in a 3% KOH solution?

Answer 16

The peptidoglycan on the cell wall will disintegrate and this releases the DNA from the cell.

The DNA can then be isolated from the solution by using a plastic rod.

Question 17

Are gram + bacteria affected by 3% KOH solution?

Answer 17

No, as their peptidoglycan is much thicker than that of gram - bacteria.

Question 18

What is a very fast way of identifying all of the bacteria in your sample?

Answer 18

A commercial bacterial identification test.

Question 19

What is an example of a commercial bacterial identification test?

Answer 19

We place cards that have been inoculated with the organism into a machine.

The machine carries out certain tests to tell us what bacteria is present.

Question 20

What is the zone of inhibition in an antibiotic susceptibility test?

Answer 20

The area around the antibiotic that bacteria will not grow in.

Question 21

What feature about the zone of inhibition tells us how effective the antibiotic is?

Answer 21

The larger the area of inhibition, the more effective the antibiotic is.

Question 22

How do we carry out antibiotic susceptibility testing?

Answer 22

By placing discs covered with antibiotics into a bacterial sample.

Question 23

What is the minimum inhibitory concentration?

Answer 23

The minimum dose necessary to inhibit the growth of the bacterial colony.

Question 24

What agar is antibiotic sensitivity testing carried out on?

Answer 24

Mueller Hinton agar.

Question 25

Why is antibiotic sensitivity testing carried out on Mueller Hinton agar?

Answer 25

As the antibiotic can diffuse through this agar.

Question 26

What does immunological testing involve?

Answer 26

Testing for bacterial antibodies within an animal.

Question 27

What immunological test can we use to test for brucellosis?

Answer 27

A bacterial agglutination test.

Question 28

What immunological test can we use to test for streptococci or the toxin of clostridium perfringens?

Answer 28

The latex particle agglutination.

Question 29

What immunological test can we use to test for black leg?

Answer 29

The fluorescent antibody test.

Question 30

What immunological test can we use to test for lyme disease?

Answer 30

The ELISA test.

Question 31

What immunological test can we use to test for E.coli?

Answer 31

Serotyping.

Question 32

What immunological test can we use to test for tuberculosis?

Answer 32

Delayed hypersensitivity test.

Question 33

How is the agglutination test for brucella carried out?

Answer 33

Blood is removed from the animal and mixed with killed brucella organisms.

If there is clumping then the test is positive.

Question 34

How do we carry out a delayed hypersensitivity test?

Answer 34

We measure the thickness of the skin and then inject antigens into the skin.

We then measure any changes in size and this tells us whether the test is positive or negative.