An improved selective medium for the isolation of Escherichia coli O 157 Chapman, P. A. and Siddons, Christine A. and Zadik, P. M. and Jewes, Linda,, 35, 107-110 (1991), doi = https://doi.org/10.1099/00222615-35-2-107, publicationName = Microbiology Society, issn = 0022-2615, abstract= Summary. Sorbitol-MacConkey medium has become widely used for the isolation of verotoxigenic (VT+) Escherichia coli O157. However, many organisms other than VT+ E. coli O157, especially other serogroups of E. coli and Proteus spp., may not ferment sorbitol, and thus may be confused initially with VT+ E. coli O157. Rhamnose is not fermented by VT+ E. coli O157, but is by most sorbitol non-fermenting E. coli of other serogroups. Cefixime is a cephalosporin antibiotic that is more active against Proteus spp. than against E. coli. Inclusion of rhamnose and cefixime in sorbitol-MacConkey agar improves its selectivity for the isolation of VT+ E. coli O157., language=, type=