Eosin-methylene blue agar is commonly used for growing which type of bacteria?

Eosin-methylene blue (EMB) agar is a selective differential medium primarily utilized for the cultivation of Gram-negative bacteria, particularly members of the Enterobacteriaceae family, such as Escherichia coli and Enterobacter. The dyes eosin and methylene blue in the agar inhibit the growth of Gram-positive bacteria, which allows for the selective isolation of Gram-negative organisms.

In addition to selectivity, EMB agar also provides a means of differentiating among Gram-negative bacteria based on their fermentation abilities. For instance, lactose fermenters produce acid that reacts with the indicators in the medium, resulting in color changes—typically producing a metallic green sheen for strong fermenters like E. coli.

Thus, the specificity of EMB agar for Gram-negative bacteria, as well as its ability to distinguish between lactose fermenters and non-fermenters, confirms its role as a valuable tool in microbiological studies focused on this group of microorganisms.