Hektoen Enteric Agar (HEK, HE or HEA) is a selective and differential agar mainly used to recover salmonella and shigella from patient samples. Compared to other selective culture media (e.g. SS agar, GLP agar and bismuth sulfite agar), Hektoen Enteric Agar has the advantage of only slightly inhibiting the growth of Salmonella and Shigella, resulting in high yields of these microorganisms, while ensuring adequate inhibition of accompanying microorganisms. Lactose-positive colonies have a distinctly different color from lactose-negative colonies due to the presence of the two indicators bromothymol blue and acid fuchsin. This color difference is also observed for colonies that can only ferment lactose slowly due to the presence of sucrose and salicin. These reactive compounds can be fermented more easily - false positive pathogenic results are thus avoided. The combination of thiosulfate as a reactive compound with an iron salt as an indicator causes the H2S-positive colonies to turn black. The bile salt mixture suppresses the growth of most accompanying microorganisms.