Ans. is 'a' i.e.. Sorbitol containing agar Culture of 0157: H7 E.colio E.coli 0157:H7 is not identified on routine stool cultures.o E.coli 0157:H7 can be specifically detected by the use of modified Mac Conkey media which containssorbitol in place of lactose (SMAC).o Sorbitol Mac Conkey media is specifically useful for the detection of E.coli 0157:H7 as unlike most strains of E. coli, the 0157: H7 strain does not ferment sorbitol.o Non fermenting colonies on a Sorbitol Mac Conkey plate (SMAC) therefore suggest the diagnosis of E.coli 0157:H7.o Sorbitol Mac Conkey media is the screening method of choice for E.coli Ol57:H7.