MacConkey Sorbitol HiCynthâ„¢ Agar (Sorbitol HiCynthâ„¢ Agar) is recommended for isolation of enteropathogenic Escherichia coli O157: H7. E.coli O157:H7 grows as colourless colonies on this medium wile most of the faecal flora that ferment sorbitol appear as pink coloured colonies. This medium is prepared by completely replacing animal peptones with chemically defined peptones to avoid BSE/TSE/GMO risks associated with animal peptone.