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28: EMB Agar

  • Page ID
    90574
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    Eosin-Methylene Blue (EMB) agar is a selective & differential medium used to isolate Gram-negative enteric bacteria and distinguish between them. EMB contains 2 dyes--Eosin and methylene blue--which act as selective agents to inhibit Gram-positive bacteria but allow for the growth of Gram-negative bacteria.

    EMB also contains the sugars lactose and sucrose--and it distinguishes or differentiates between lactose or sucrose fermenters from non-fermenters. The fermenters form colored colonies and the non-fermenters form colorless colonies, similar to the MacConkey agar.

    EMB plate with E. coli

    Figure 1: Eosin-methylene blue ( EMB) agar plate inoculated with Escherichia coli (a Gram-negative coliform bacterium) showing good growth of dark blue-black colonies with metallic green sheen indicating vigorous fermentation of lactose and acid production which precipitates the green metallic pigment. Image by Naowarat Cheeptham, Thompson Rivers University, Kamloops, BC, Canada.


    This page titled 28: EMB Agar is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Rosanna Hartline.

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