KM0032 – Hektoen Enteric Agar

//KM0032 – Hektoen Enteric Agar

KM0032 – 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 indicator

in 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.

Additional Information

Shelf Life (days)

Storage Temp (°C)

Dehydrated Medium Appearance

Prepared Medium Appearance

Dehydrated Medium Colour

Prepared Medium Colour

Dehydrated PH

Prepared PH

Product Description

OrganismRef. No.Result
Salmonella thyphimuriumNCTC 12023Growth, translucent colonies with black centre
Shigella flexneriATCC 12022Growth, green colonies
Enterococcus faecalisNCTC 12697Partial inhibition
Escherichia coliNCTC 12241Partial inhibition

Formula*

FORMULA*g/l
Meat peptone12
Yeast Extract3
Sucrose12
Lactose12
Salicin2
Sodium deoxycholate2.4
Bile salts7
Sodium chloride5
Sodium thiosulfate5
Ferric ammonium citrate1.5
Acid fuchsin0.1
Bromothymol blue0.065
Agar14
Total76

Preparation

Suspend 76 g of the medium in one litre of deionised / purified water. Allow the medium to soak whilst mixing for 10 minutes. Heat with frequent agitation and boil for one minute to completely dissolve the medium. DO NOT AUTOCLAVE this medium. Cool to 45-50°C and aseptically dispense into appropriate sterile containers