Handbook of Culture Media for Food and Water Microbiology
Chapter H1: Hektoen Enteric (HE) agar
Published:06 Dec 2011
Special Collection: 2011 ebook collection , 2011 ebook collection , 2011-2015 food science subject collection
2011. "Hektoen Enteric (HE) agar", Handbook of Culture Media for Food and Water Microbiology, Janet E L Corry, Gordon D W Curtis, R M Baird
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This medium for the isolation of Shigella and Salmonella was originally developed by King and Metzger (1968) of the Hektoen Institute. It relies on the use of bile salts for selective inhibition and two indicator systems: (i) bromothymol blue and acid fuchsin as indicators of carbohydrate dissimilation and (ii) ferric iron as an indicator of the formation of hydrogen sulfide from thiosulfate. HE agar allows good growth of Shigella spp. because the inhibition of these organisms by bile salts is reduced by the addition of relatively large amounts of peptone and carbohydrates. The medium provides good colonial differentiation and inhibits some coliforms and other non-lactose-fermenting bacteria, thereby facilitating the identification of Salmonella and Shigella from food products.