Hektoen enteric agar is a selective and differential agar primarily used to recover Salmonella

Salmonella

Salmonella is a genus of rod-shaped, Gram-negative, non-spore-forming, predominantly motile enterobacteria with diameters around 0.7 to 1.5 µm, lengths from 2 to 5 µm, and flagella which grade in all directions . They are chemoorganotrophs, obtaining their energy from oxidation and reduction...

 and Shigella

Shigella

Shigella is a genus of Gram-negative, nonspore forming, non-motile, rod-shaped bacteria closely related to Escherichia coli and Salmonella. The causative agent of human shigellosis, Shigella causes disease in primates, but not in other mammals. It is only naturally found in humans and apes. During...

 from patient specimens. HE contains indicators of lactose

Lactose

Lactose is a disaccharide sugar that is found most notably in milk and is formed from galactose and glucose. Lactose makes up around 2~8% of milk , although the amount varies among species and individuals. It is extracted from sweet or sour whey. The name comes from or , the Latin word for milk,...

 fermentation and H₂S production; as well as inhibitors to prevent the growth of gram positive bacteria. The pattern of lactose fermentation and H₂S production aids in the identification of the organism subbed to the plate. Specifically, Salmonella produces black colonies, whereas Shigella produces translucent green colonies. The color of the agar itself is green. Sugars in media usually include lactose, sucrose, and salicin.

External links

• More details of HEK