Hektoen Enteric Agar

Hektoen enteric agar was developed by King and Metzger as a differential selective medium for the isolation of Shigella spp. and Salmonella spp. species from enteric pathological samples.

The meat peptone and yeast extract provide the required nitrogen, carbon and vitamins. Lactose, sucrose and salicin are fermentable carbohydrates. Bromothymol blue is added as a pH indicatorin order to identify carbohydrate fermenting organisms.

The combination of ferric ammonium citrate and sodium thiosulfate allows the production of hydrogen sulphide. Hydrogen sulphide positive colonies produce black centred colonies. Sodium chloride maintains the osmotic balance. The bile salts and acid fuchsin inhibit Gram-positive organisms.

A differential selective medium for the isolation of Shigella spp. and Salmonella spp. species from enteric pathological samples.

Additional Information

Shelf Life (days): 1095 days

Storage Temp (C): 10-30C

Dehydrated Medium Appearance: Fine Powder

Prepared Medium Appearance: Firm Gel

Dehydrated Medium Colour: Light Green/Beige

Prepared Medium Colour: Green

Dehydrated PH: 7.5 0.2

Prepared PH: 7.5 0.2

Recommended Incubation: Aerobically at 35-37C for 18-24 hours

Formula*g/l

Meat peptone: 12

Yeast Extract: 3

Sucrose: 12

Lactose: 12

Salicin: 2

Sodium deoxycholate: 2.4

Bile salts: 7

Sodium chloride: 5

Sodium thiosulfate: 5

Ferric ammonium citrate: 1.5

Acid fuchsin: 0.1

Bromothymol blue: 0.065

Agar: 14

Total: 76