Which Enterobacteriaceae species are often tested for their ability to ferment sorbitol?

The species Escherichia coli O157:H7 is specifically tested for its ability to ferment sorbitol because this strain is known for its public health significance and its association with severe foodborne illnesses. When cultured on sorbitol-MacConkey agar, non-sorbitol-fermenting colonies of E. coli O157:H7 appear as colorless or pale compared to pink colonies of other E. coli strains that do ferment sorbitol. This biochemical test is particularly useful in identifying E. coli O157:H7 in clinical and food samples, contributing to outbreak investigations and ensuring food safety.

Testing for sorbitol fermentation is a distinct method used to differentiate this pathogenic strain from other non-pathogenic strains of E. coli that typically can ferment sorbitol. Other species within the Enterobacteriaceae family have different biochemical properties and do not serve the same purpose in the context of identifying E. coli O157:H7 through sorbitol fermentation.