Hektoen Enteric Agar

/Hektoen Enteric Agar

Hektoen Enteric Agar

Cat. Number: CM-HEA207 Categories: , ,

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Description

Use and description:

For the isolation and cultivation of Gram-negative enteric microorganisms (Salmonella and Shigella) from clinical specimens. Salicin, sucrose and lactose fermenting bacteria appear as yellow to orange colonies. H2S producing organisms appear as colonies with black centres because of the presence of ferric citrate which forms iron sulphide. Bile salts inhibits most of Gram positive bacteria. Non fermenting Salmonella and Shigella colonies are blue green. The additional carbohydrate (sucrose) and salicin with the high concentration of peptones give better growth of Salmonella and Shigella spp.

 

Composition per litre:

Peptones……………………………………..………12.0g

Yeast extract……………………………….…………3.0g

Sodium chloride………………………..…………..5.0g

Agar……………………………………………………..14.0g

Lactose…………………………………………..…….12.0g

Saccharose…………………………………..……….12.0g

Bile salt no. 3.……………………………….…………2.0g

Sodium thiosulphate……………….…….………..5.0g

Salicin………………………………………………..……2.0g

Ferric ammonium citrate…………………………1.5g

Acid fuchsin…………………………………….…..0.100g

Bromthymol blue…………………………..……..0.06g

 

Final pH of the ready to use medium: 7.5 ± 0.2

 

Medium preparation:

Add 69.1 grams of dehydrated culture medium to 1 litre of distilled water. Heat with repeated stirring and boil for one minute to dissolve completely. DO NOT AUTOCLAVE OR OVERHEAT THIS MEDIUM. Pour plates can be prepared after the medium has cooled to 45-50°C.

 

Quality specifications:

Dehydrated medium: homogeneous, light greenish-beige fine powder. Ready to use medium: clear to trace hazy and light to dark green in colour.

 

Microbiological response:

Organism Result
Enterobacter aerogenes ATCC 13048 Growth/yellow to salmon coloured colonies with bile precipitate
Escherichia coli ATCC 25922 Inhibited/yellow-orange bile
Proteus vulgaris ATCC 13315 Inhibited/clear to yellowish
Salmonella typhimurium ATCC 14028 Growth/green black centres
Shigella flexneri ATCC 12022 Growth/blue-green colonies

 

Storage:

Dehydrated medium should be stored between 10 to 25°C. Once opened, place the container in a dark, dry place. The dehydrated medium should not be used if there is any lump or the colour has changed from the original.