Eosin Methylene Blue Agar Flashcards, test questions and answers

Discover flashcards, test exam answers, and assignments to help you learn more about Eosin Methylene Blue Agar and other subjects. Don’t miss the chance to use them for more effective college education. Use our database of questions and answers on Eosin Methylene Blue Agar and get quick solutions for your test.

What is Eosin Methylene Blue Agar?

Eosin Methylene Blue Agar, commonly referred to as EMBA, is a selective and differential medium used for the isolation and identification of certain bacterial species. This growth medium contains eosin Y dye which has a high affinity for Gram-positive bacteria and methylene blue dye which has a high affinity for Gram-negative bacteria. Additionally, this agar also contains an indicator system (a combination of sugars) that differentiates between lactose fermenters and non-lactose fermenters. As such, EMB Agar can be used to differentiate between various species of microorganisms based on their color reactions when grown on the surface or in butt sections of the plate. EMB Agar is considered one of the most useful media due to its ability to produce distinct colonies with visible color differences that are easily distinguishable from each other. It works by creating an environment where both Gram-positive and Gram-negative organisms can be clearly differentiated from each other based on their staining characteristics upon inoculation onto the agar surface. For example, when enteric bacilli such as Salmonella or Shigella are grown on EMB Agar, they will appear deep red because these bacteria contain large amounts of indole. In contrast, when Staphylococcus aureus is cultured on EMB Agar it appears yellowish green due to lack of Indole production. In addition to being able to differentiate different bacterial groups based on their staining characteristics upon inoculation onto the agar surface, EMB agar is also capable of detecting whether or not certain organisms are capable of fermenting specific carbohydrates (such as lactose). This detection occurs through an indicator system composed primarily of sucrose and lactose sugar mixtures in order to determine if organisms have been able to metabolize either one type or both types of sugars resulting in an acid reaction (byproducts produced during fermentation) which changes the pH level making it more acidic than neutral thus causing characteristic colors within colonies found growing around those particular areas on plates known as Butts. An alkaline reaction indicates no fermentation occurred while yellow/green colored colonies indicate successful fermentation occurred while clear zones indicate unsuccessful fermentation took place.