A stool culture can detect the bacterium, although it is not a routine test and so must be specifically requested. The sample is cultured on sorbitol-MacConkey (SMAC) agar, or the variant cefixime potassium tellurite sorbitol-MacConkey agar (CT-SMAC). On SMAC agar,<unk> :H7 colonies appear clear due to their inability to ferment sorbitol, while the colonies of the usual sorbitol-fermenting serotypes of E. coli appear red. Sorbitol nonfermenting colonies are tested for the somatic<unk>  antigen before being confirmed as E. coli<unk> :H7. Like all cultures, diagnosis is time-consuming with this method; swifter diagnosis is possible using quick E. coli DNA extraction method plus PCR techniques. Newer technologies using fluorescent and antibody detection are also under development.
Escherichia coli O157:H7
Escherichia coli O104:H4
Escherichia coli O121
Escherichia coli O104:H21
Campylobacter upsaliensis
Enteroaggregative Escherichia coli
Salmonella
Vibrio cholerae