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Flashcards in Selective and Differential Tests Deck (34)
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1

A media that encourages the growth of some organisms but suppresses the growth of others

Selective Media

2

This media causes an observable change (color or change in pH) in the medium when a particular biochemical reactions occurs. So most bacteria will grow, but they will grow different colors based on their interaction with the media

Differential Media

3

This media contains special nutrients that allow growth of a particular organism that might not otherwise be present in sufficient numbers.

Enrichment Media

4

Used for the isolation and differentiation of Staphylococcus Aureus

Mannitol Salt Agar (MSA)

5

What makes the MSA agar selective

Sodium Chloride (Salt)

6

Staphylococcus bacteria thrive in high salt concentrations. But what happens to other bacteria such a E.coli

They Dehydrate (shrivel) and die

7

What makes the MSA agar differential

The Mannitol

8

If Staphylococcus bacteria ferment the Mannitol what color will the growth be

Yellow

9

If Staphylococcus bacteria do not ferment the Mannitol what color will the growth be

Pink

10

When Mannitol is fermented what happens to the pH in the media

Because acids are released the pH goes down

11

Used to isolate and differentiate members of enterobacteriaceae based on the ability to ferment lactose

MacConkey Agar (MAC)

12

What makes the MAC agar selective

Bile salts and crystal violet

13

In MAC agar what type of bacteria are inhibited from growing

Gram positive bacteria

14

In MAC agar what makes the media differenital

The lactose

15

When bacteria such as E.coli ferment lactose what color is the growth on a MAC agar plate

Pink

16

Used for the isolation of fecal coliforms

Eosin Methylene Blue Agar (EMB)

17

What sugars are present in an EMB agar plate

Sucrose and Lactose

18

What type of bacteria are inhibited from growing on an EMB plate

Gram positive bacteria

19

What components of the EMB plate make it selective

Eosin Y Dye and Methylene Blue

20

What type of bacteria typically grow with a metallic green sheen on an EMB plate?

E.coli

21

What color will the bacteria grow on an EMB plate if they ferment sucrose?

They retain the color of the medium.

22

What color will the bacteria grow on an EMB plate is they ferment lactose?

Depending on the bacteria it could be dark purple, black or metallic green.

23

The citrate test is used to determine the ability of an organism to use citrate as its sole source of _____

Carbon

24

The enzyme _______ will transport citrate to the cell and perform citrate fermentation

Citrate Permease

25

Will the pH of the Citrate media increase or decrease after citrate has been utilized

Increase

26

A citrate positive test will turn which color (assuming you add enough bacteria)

Blue

27

During a urea test you are testing bacteria to see if they have what enzyme?

The enzyme urease

28

How long do you have to read the results of a urea test?

24 hours

29

Will the pH of the media increase or decrease when urea is broken down?

Increase

30

What color is a positive urea test?

Pink

31

Allows for differentiation of bacteria based on their ability to hemolyze RBCs

Blood Agar

32

The complete destruction of RBCs and hemoglobin, results in a clear growth around the colonies

Beta Hemolysis

33

The partial destruction of RBCs and produces a greenish discoloration of agar around the colonies.

Alpha Hemolysis

34

Non-hemolysis and appears as simple growth with no change to the medium.

Gamma Hemolysis