Hektoen enteric agar is a medium designed for the isolation and recovery of fecal specimens belonging to the Enterbacteriaceae family, especially Salmonella and Shigella. It can differentiate between bacteria that ferment lactose and those that don't. Acid produced from fermenting lactose imparts a yellow-orange color to the medium due to the presence of a pH indicator. Non-lactose fermenters do not significantly change the color of the medium. HE agar can also detect the production of hydrogen sulfide gas, which turns parts of the medium black.

	发酵乳糖的某种肠杆菌。
	不发酵乳糖的某种肠道菌，而且产生硫化氢，可能是沙门氏菌
	不发酵乳糖的肠道菌，可能就是志贺氏菌。