Which agar is specifically used to differentiate E. coli O157:H7?

Sorbitol-MAC agar (Sorbitol-MacConkey agar) is specifically used to differentiate E. coli O157:H7 from other strains of Escherichia coli. This particular strain has the unique characteristic of not fermenting sorbitol, which is a sugar alcohol that many other E. coli strains can ferment.

When E. coli O157:H7 is cultured on Sorbitol-MAC agar, it will produce colorless colonies because it does not ferment sorbitol and thus does not produce acid that would turn the agar pink. In contrast, typical E. coli strains that can ferment sorbitol will produce pink colonies on this medium.

In clinical microbiology, identifying E. coli O157:H7 is crucial due to its association with severe gastrointestinal illness and potential complications, such as hemolytic uremic syndrome. Sorbitol-MAC agar's ability to exploit this metabolic difference makes it an essential tool in laboratories for the investigation of suspected foodborne outbreaks or gastrointestinal infections.

Other agar types mentioned in the options, while useful for different purposes, do not provide the same level of differentiation specifically for E. coli O157:H7. For example, Mannitol Salt Agar is primarily selective for St