Sorbitol MacConkey Agar is used for the isolation of pathogenic Escherichia coli in a laboratory setting. Sorbitol MacConkey Agar is not intended for use in the diagnosis of disease or other conditions in humans.
Sorbitol MacConkey Agar is based on the formula by Rappaport and Henig. Originally developed for isolating enteropathogenic (EPEC) serotypes, O11 and O55, this medium is recommended for the isolation and differentiation of enterohemorrhagic E. coli O157:H7. Serotype O157 has been implicated in serious foodborne diseases.
MacConkey Agar W/ Sorbitol contains sorbitol instead of lactose for differentiating enteropathogenic E. coli serotypes; these strains are typically sorbitol negative. MacConkey Agar W/ Sorbitol is recommended for food testing.
Enzymatic Digest of Gelatin, Enzymatic Digest of Casein, and Enzymatic Digest of Animal Tissue are the nitrogen and vitamin sources in MacConkey Agar W/ Sorbitol. Sorbitol is the fermentable carbohydrate; typically enteropathogenic strains produce colorless colonies. Bile Salts Mixture and Crystal Violet are the selective agents, inhibiting Gram-positive cocci. Sodium Chloride maintains the osmotic environment, and Neutral Red is the pH indicator. Agar is the solidifying agent. The selectivity of the medium can be increased through the addition of Cefixime and tellurite.
