Pseudomonas is referred to as an oxidase positive bacteria while E. Coli is an oxidase negative bacteria. The use of the oxidase test will be helpful in the differentiation of the two Bacteria according to their oxidase activity/properties.
Colonies of Red without black center color is what is expected on HE agar if shigellosis is suspected.
Colonies of Salmon/Orange color is what is expected on HE agar if Enterococcus sp. is suspected.
