Lysine Decarboxylase Test/ Kigler Iron Agar Test

Question 1

What is the purpose of the Lysine Decarboxylase Test?

Answer 1

to detect the presence of lysine decarboxylase

Question 2

What is the application of Lysine Decarboxylase Test?

Answer 2

differentiate GNR

Question 3

What medium is used for Lysine Decarboxylase Test? What else is found in that media?

Answer 3

Mollers Lysine Decarboxylase Medium

• peptone: nutrients
• glucose: induce fermentation
• lysine: amino acid substrate for lysine decarboxylase
• bromcresol purple: pH indicator
  
  • acidic: yellow
  • neutral: gray
  • basic: purple

Question 4

What is the inoculation guide for Lysine Decarboxylase Test??

Answer 4

loopful; layer with mineral oil (keep O2 out and induce fermentation)

Question 5

What is the incubation guide for Lysine Decarboxylase Test??

Answer 5

37C for 48 hours

Question 6

What is the theory of Lysine Decarboxylase Test??

Answer 6

Decarboxylation will occur if amino acid is present (already in media), low pH environment: glucose and mineral oil –>induce fermentation

lysine decarboxylation breaks down lysine into cadauarine and CO2

Question 7

What are the results of Lysine Decarboxylase Test?

Answer 7

(+)- purple

-)- gray/ yellow (no change

Question 8

What is the purpose of the Kigler Iron Agar Test?

Answer 8

to determine if your organism ferments glucose, lactose; reduces hydrogen sulfide

Question 9

What is the application of the Kigler Iron Agar Test?

Answer 9

differentiate GNR

Question 10

What media is used for the Kigler Iron Agar Test? what else is found in it?

Answer 10

Kigler iron media

• 0.1% glucose: fermentable sugar, low concentration
• 1% lactose: fermentable sugar, high concentration
• 0.02% ferrous sulfate: detects hydrogen sulfide
• phenol red: pH indicator
• nutrient agar

Question 11

What is the theory/ results for Kigler Iron Agar Test?

Answer 11

ferments only glucose

• yellow butt: acid reacts with phenol red
• slant/ red butt: after the low concentration of glucose is used, amino acid oxidation follows fermentation

Ferment lactose or lactose/glucose:

• yellow butt: acid reacting with phenol red
• yellow slant: acid reacting with phenol red, high concentration of lactose

Hydrogen sulfide production: black precipitate
- H2S reacts with ferrous sulfate to form black ppt

Gas production:
-butt lift