APPEARANCE OF ENTEROBACTERIACEAE ON SELECTED MEDIA

Question 1

What does TSI stand for in microbiological media?

Answer 1

Triple Sugar Iron

Question 2

What are the three sugars present in TSI media?

Answer 2

Glucose, lactose, and sucrose

Question 3

True or False: Enterobacteriaceae can ferment lactose in MacConkey agar.

Answer 3

True

Question 4

What color indicates lactose fermentation on MacConkey agar?

Answer 4

Pink

Question 5

What type of bacteria does HEKTOEN Enteric agar primarily differentiate?

Answer 5

Enteric Gram-negative bacteria

Question 6

What color do H2S-producing bacteria turn on HEKTOEN Enteric agar?

Answer 6

Black

Question 7

Fill in the blank: XLD agar is selective for __________.

Answer 7

Enterobacteriaceae

Question 8

What does the ‘X’ in XLD agar stand for?

Answer 8

Xylose

Question 9

What color indicates xylose fermentation on XLD agar?

Answer 9

Yellow

Question 10

True or False: TSI media can be used to detect hydrogen sulfide production.

Answer 10

True

Question 11

What indicates a gas production in TSI media?

Answer 11

Cracks or lifting in the agar

Question 12

What is the pH indicator used in TSI media?

Answer 12

Phenol red

Question 13

What color does TSI turn when acid is produced?

Answer 13

Yellow

Question 14

Which Enterobacteriaceae is characterized by producing a blue-green pigment on HEKTOEN Enteric agar?

Answer 14

Enterobacter aerogenes

Question 15

What is the selective agent in MacConkey agar?

Answer 15

Bile salts and crystal violet

Question 16

Fill in the blank: Non-lactose fermenters on MacConkey agar appear __________.

Answer 16

Colorless

Question 17

What does a yellow slant and yellow butt in TSI indicate?

Answer 17

Fermentation of glucose and lactose/sucrose

Question 18

True or False: Salmonella produces a red colony on XLD agar.

Answer 18

False

Question 19

What is the appearance of Shigella on MacConkey agar?

Answer 19

Colorless colonies

Question 20

What does HEKTOEN Enteric agar differentiate between?

Answer 20

Lactose fermenters and non-fermenters

Question 21

When testing for Enterobacteriaceae, which media is used to identify hydrogen sulfide production?

Answer 21

TSI and HEKTOEN Enteric agar

Question 22

What does a black precipitate in TSI media indicate?

Answer 22

Hydrogen sulfide production

Question 23

What color do fermenters appear on XLD agar?

Answer 23

Yellow

Question 24

What is the main carbohydrate source in XLD agar?

Answer 24

Xylose

Question 25

True or False: All Enterobacteriaceae are lactose fermenters.

Answer 25

False

Question 26

How can you differentiate E. coli from other lactose fermenters on MacConkey agar?

Answer 26

E. coli produces a pink colony with a metallic sheen

Question 27

TSI: A/A, gas MacConkey: flat, dry pink halo Hektoen Enteric: yellow XLD: Yellow

Answer 27

e. coli

Question 28

TSI: K/A MacConkey: Colorless Hektoen Enteric: green XLD: colorless

Answer 28

Shigella

Question 29

TSI: K/A, gas, H2S MacConkey: colorless Hektoen Enteric: colorless XLD: red, yellow or colorless w or w/o black centers

Answer 29

Edwardsiella

Question 30

TSI: A/A or K/A gas, w or w/o H2S MacConkey: Colorless @ 24hr, may become pink @48Hrs Hektoen Enteric: colorless XLD: red, yellow or colorless w or w/o black centers

Answer 30

Citrobacter

Question 31

TSI: K/A, gas, H2S MacConkey: Colorless Hektoen Enteric: Green XLD: Red with black center

Answer 31

Salmonella

Question 32

TSI: A/A, gas MacConkey: Pink mucoid Hektoen Enteric: yellow XLD: yellow

Answer 32

Klebsiella

Question 33

TSI: A/A gas MacConkey: pink may be mucoid Hektoen Enteric: yellow XLD: yellow

Answer 33

Enterobacter

Question 34

TSI: K/A MacConkey: Colorless @ first, turning pink. S. marcescens may have red pigement at RT Hektoen Enteric: colorless XLD: yellow or colorless

Answer 34

Serratia

Question 35

TSI: K/A (mirabilis) A/A (vulgaris) gas H2S MacConkey: Colorless may swarm Hektoen Enteric: colorless XLD: yellow or colorless, w or wo black centers

Answer 35

Proteus

Question 36

TSI: K/A gas MacConkey: colorless Hektoen Enteric: colorless XLD: red or colorless

Answer 36

Morganella

Question 37

TSI: K/A MacConkey: Colorless Hektoen Enteric: Colorless XLD: Yellow or Colorless

Answer 37

Providencia

Question 38

TSI: Yellow/ Orange MacConkey: Colorless to peach Hektoen Enteric: salmon XLD: Yellow or colorless

Answer 38

Yersinia