Studies of Escherichia coli cultured on Rainbow Agar O157 with particular reference to enterohaemorrhagic Escherichia coli (EHEC).

Rainbow Agar O157 is designed for the rapid isolation and identification of enterohaemorrhagic Escherichia coli (EHEC), particularly O157, characterised by black colonies. Five-hundred-eighty-five E. coli strains, including O157, O111 and O113 serogroups from many sources were examined on Rainbow Agar O157. EHEC O157 could readily be isolated and recognized uniquely by typical black colonies. Some other EHEC also stand out as blue-black, whereas O113 and some other EHEC strains were mauve, red or pink and indistinguishable from SLT-negative strains of E. coli.