Intro To Biochemical Testing II: Differential And Selective Media Flashcards Preview

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Flashcards in Intro To Biochemical Testing II: Differential And Selective Media Deck (28):
0

Define selective medium

Permits the growth of certain organisms while preventing or retarding the growth of others

1

What are the ways selection can be carried out through?

1. Control of ingredients of the medium
2. Alteration of atmospheric conditions
3. Adjustment of the incubation temperature

2

Define differential medium

Causes certain colonies to develop differently from other organisms present

3

What media type is the MacConkey Agar?

Selective and differential

4

Components and selective agents of MacConkey Agar are:

Bile salts, crystal violet, lactose, and neutral red.
Bile salts and crystal violet inhibit growth of gram + while lactose and neutral red help to differentiate lactose fermenters (pink colonies) and non-fermenters (clear colonies)

5

Organisms encourages to grow in MacConkey Agar:

Differentiates among gram - while inhibiting gram +

6

What media type is the Hektoen Enteric Agar?

Selective and differential

7

What components or selective agents are in Hektoen Enteric Agar?

Bile salts and sugars. Bile salts inhibit growth of gram + while the sugars help to show fermenters (yellow or pink colonies) and non-fermenters (blue or green with black centers)

8

Organisms encouraged to grow on Hektoen Enteric Agar?

Gram - rods, particularly Enterobacteriaceae family bacteria from fecal material

9

Hektoen Enteric Agar also detects:

Rapid sugar-fermenting organisms in fecal specimens and hydrogen sulfide producers

10

What media type is the Eosin Methylene Blue (EMB)?

Selective and differential

11

What components or selective agents are in Eosin Methylene Blue?

Eosin, methylene blue, lactose: eosin and methylene blue inhibit growth of gram + bacteria while lactose fermenters appear purple-pink (low acid) or metallic green (high acid) and have a dark center. Non-lactose fermenters appear colorless

12

Organisms encouraged to grow on Eosin Methylene Blue

Gram - rods, particularly Enterobacteriaceae family bacteria from fecal material

13

What media type is Mannitol-Salt Agar (MSA)?

Selective and differential

14

What components or selective agents are in Mannitol-Salt Agar?

Mannitol and sodium chloride: mannitol differentiates. If mannitol fermentation occurs, lactic acid produced, pH drops making plate yellow. Salt portion selective for halophiles (orgs that survive high salt conc.), orgs that can't withstand high salt content will not grow.

15

What organism is encouraged to grow on Mannitol-salt Agar?

Halophiles, including Staphylococcus aureus

16

What media type is blood agar?

Differential

17

What components or selective agents are in blood agar?

Blood from a mammal to show the organisms reaction to hemoglobin and it's capability to break down hemoglobin.

18

Organisms encouraged to grow on blood agar:

Used to isolate fastidious organisms and detect hemolytic activity

19

What is alpha hemolysis?

Incomplete breakdown of hemoglobin. Results in formation of green zone around colonies in blood agar

20

What is beta hemolysis?

Complete breakdown of hemoglobin. Creates clear zone around colonies in blood agar

21

What is gamma hemolysis?

No reaction. Absence of any visible reaction around colonies in blood agar.

22

What media type is Tryptic Soy Agar (TSA)?

General purpose

23

Components or selective gents of Tryptic soy agar?

General purpose media produced via enzymatic digestion of soybean meal and caesin

24

How can one enhance resolution?

Better optics

25

What is the max. resolution of a light microscope?

0.2 μm

26

What is the max. resolution of SEM?

1nm

27

What is the max. resolution of TEM?

0.5 nm