Levine's Eosin Methylene Blue (EMB)

Purpose:  To isolate and differentiate between various members of the family Enterobacteriaceae.

Principle:  EMB is an undefined selective/differential medium.  It contains aniline dyes (methylene blue and eosin), which inhibit the growth of Gram-positive bacteria selecting for Gram-negative bacteria.  EMB also contains lactose which makes the media differential based on an organisms ability to ferment lactose.