Kligler Iron Agar

Peptone digest of casein and meat peptone provide nitrogen, vitamins, minerals and amino acids essential for growth. Yeast extract is a source of vitamins, particularly of the B-group. Glucose and lactose are the fermentable carbohydrates producing acid, indicated by the phenol red indicator. The color changes that result are yellow for acid production and red for alkalinization. Sodium thiosulfate is reduced to hydrogen sulfide, which reacts with the iron salt to give the black iron sulfide. Sodium thiosulfate is the H₂S indicator. Ferrous sulfate provides sources of sulfates and metallic ions. Bacteriological agar is the solidifying agent.

Interpretation of color changes:

• Yellow: glucose-positive (fermentation of glucose).
• Red or without changes: glucose-negative (glucose doesn't ferment).
• Black: formation of H₂S.
• Bubbles: formation of gas.

Slanted position:

• Yellow: lactose-positive (use of lactose).
• Red or without change: lactose-negative (no use of lactose).

Preparation

Suspend 57.5 grams of the medium in one liter of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. Dispense into tubes and sterilize in autoclave at 121 °C for 15 minutes. Allow to cool in a slanted position in order to obtain butts of 1.5-2.0 cm depth.

Instructions for use

Once the colonies are purified in the Nutrient Agar (LC-1060), spread them on Kligler Iron Agar and incubate at 30 °C for 24-48 hours.

• ISO 10273:2003 Microbiology of food and animal feeding stuffs - Horizontal method for the detection of presumptive pathogenic Yersinia enterocolitica.