Enterobacter bacteria (Enterobacter aerogenes) colonies being cultured on an agar growth medium in a petri dish. E. aerogenes is part of the flora found in the human intestines. As an opportunistic pathogen it may infect immuno-compromised patients in the urinary and respiratory tracts. It rarely infects healthy people. Grown on eosin methylene blue (EMB) agar. EMB agar contains the indicator dyes eosin and methylene blue. These allow the identification and isolation of certain bacteria, and so EMB agar is a differential agar.