Rainbow O157 agar (BIOLOG, Inc.), a new selective and differential medium, was incorporated into the SELeCT system (14) (an acronym for a diagnostic system of isolation, identification, and detection of Salmonella spp., E. coli O157:H7, Listeria monocytogenes, and Campylobacter spp. in raw red meat and poultry) of isolation and identification of E. coli O157:H7 in foods to enhance the specificity for E. coli O157: H7.