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.
 | 發(fā)酵乳糖的某種腸桿菌。 |
 | 不發(fā)酵乳糖的某種腸道菌，而且產(chǎn)生硫化氫，可能是沙門氏菌 |
 | 不發(fā)酵乳糖的腸道菌，可能就是志賀氏菌。 |
