MacConkey Sorbitol Agar Base w/ Rhamnose is recommended for improved differentiation of Escherichia coli O157:H7 from background flora. This medium contains two sugars as sorbitol and rhamnose. Since Escherichia coli O157:H7 do not usually ferment sorbitol or rhamnose it appears as colourless to straw coloured colonies. While rhamnose positive and sorbitol negative appear as pink or red coloured colony and it should not be counted as presumptive Escherichia coli O157:H7. Addition of cefixime significantly reduces the number of sorbitol non-fermentors that are to be screened during the attempted isolation of Escherichia coli O157: H7.