Eosin methylene blue agar (EMB) is a selective and differential medium used to isolate fecal coliforms. Eosin Y and methylene blue are pH indicator dyes which combine to form a dark purple precipitate at low pH; they also serve to inhibit the growth of most Gram positive organisms.

Is EMB a differential or selective media?

EMB agar contains peptone, lactose, sucrose, and the dyes eosin Y and methylene blue; it is commonly used as both a selective and a differential medium. EMB agar is selective for gram-negative bacteria.

Are MacConkey and EMB agar selective differential or both?

Both emb and macconkey agars are differential and selective, for gram-negative enteric bacteria.

What type of media is EMB agar?

Eosin Methylene Blue (EMB) agar is a differential microbiological medium, which slightly inhibits the growth of Gram-positive bacteria and provides a color indicator distinguishing between organisms that ferment lactose (e.g., E. coli) and those that do not (e.g., Salmonella, Shigella).

Which of the following media is both selective and differential?

MacConkey agar is an example of a medium that is both differential and selective. The presence of bile salts, as well as crystal violet, within the media prevent gram-positive organisms from growing.

Is EMB agar defined or undefined?

Is EMB agar a defined or an undefined medium? Provide the reasoning behind your choice and explain why this formulation is desirable. EMB agar is an undefined medium. It contains multiple ingredients in which the composition is unknown, including beef extract and pancreatic digest of gelatin.

What does an EMB plate selective for quizlet?

-Eosin Methylene Blue (EMB) agar are selective for Gram-negative organisms and contain indicators to differentiate lactose fermenters from lactose non-fermenters.

Is EMB Agar complex or defined?

EMB agar is an example of a selective medium, a differential medium, and a complex medium. Haemophilus influenzae must be grown on chocolate agar, which is blood agar treated with heat to release growth factors in the medium.

Why are crystal violet agar and 7.5% sodium chloride agar considered selective media?

Why are crystal violet agar and 7.5% sodium chloride agar considered selective media? They are used to select or isolate specific bacteria. Gram-positive organisms are very sensitive to the basic dye in CV. NaCL produces an osmotic environment not conductive for any organism besides halophiles.

What type of bacteria does EMB Agar inhibit?

EMB is a differential microbiological medium, which slightly inhibits the growth of Gram-positive bacteria and provides a color indicator distinguishing between organisms that ferment lactose (e.g., E. coli) and those that do not (e.g., Salmonella, Shigella).

Article first time published on

What does the EMB Agar have in common with the MacConkey Agar?

How is MacConkey Agar similar to EMB agar? 1. They are both used to differentiate lactose fermenters from non lactose fermenters.

What makes the identified media selective and/or differential?

Selective media generally selects for the growth of a desired organism, stopping the growth of or altogether killing non-desired organisms. Differential media takes advantage of biochemical properties of target organisms, often leading to a visible change when growth of target organisms are present.

Which of the following is not an example of selective media?

Which of the following is not an example of selective media? Explanation: Tryptic Soy is an example of broth which is used in broth formula. Mannitol agar, MacConkey’s agar, crystal violet blood agar, Thayer Martin agar, etc.

What is the main use of the EMB agar plate?

Eosin Methylene Blue (EMB) agar is both a selective and differential culture medium. It selectively promotes the growth of Gram-negative bacteria (inhibits Gram-positive bacteria) and aids in the differentiation of lactose fermenter and non-lactose fermenting colonies.

What type of agar is EMB select all that apply?

EMB is a selective, differential agar medium used for isolation of gram negative rods in a variety of specimen types.

What is the function of the 7.5% NaCl in mannitol salt agar?

It contains a high concentration (about 7.5–10%) of salt (NaCl) which is inhibitory to most bacteria – making MSA selective against most Gram-negative and selective for some Gram-positive bacteria (Staphylococcus, Enterococcus and Micrococcaceae) that tolerate high salt concentrations.

Which of the components gives EMB media is selective properties?

Eosin Methylene Blue (EMB) Agar: is a selective AND a differential medium. The selective components are the eosin and methylene blue dyes that inhibit the growth of Gram-positive bacteria and permit the growth of Gram-negative enteric rods.

Which of the components gives EMB media its selective properties Why?

EMB contains the dyes eosin and methylene blue that inhibit the growth of gram-positve bacteria. Therefore, EMB is selective for gram-negatives. In addition, the gram-negatives that grow can be differentiated based on their ability to ferment lactose.

Are Uninoculated controls positive or negative?

Were the uninoculated controls in this lab positive or negative, and what purpose did they serve? The controls were negative, and served as color comparison for experimental tubes as well as verification for media sterility.

Which media are selective and differential quizlet?

For what is MacConkey Agar selective and differential? Selective: for Gram-negative bacteria because bile salts and crystal violet inhibit the growth of Gram-positive bacteria. Differential: based on ability to ferment lactose (bacteria that can ferment lactose cause a drop in pH which turns indicator pink).

What are examples of selective media?

• Eosin methylene blue contains dyes that are toxic for Gram-positive bacteria. …
• YM (yeast extract, malt extract agar) has a low pH, deterring bacterial growth.
• MacConkey agar is for Gram-negative bacteria.
• Hektoen enteric agar is selective for Gram-negative bacteria.

Is mannitol salt agar selective or differential?

This type of medium is both selective and differential. The MSA will select for organisms such as Staphylococcus species which can live in areas of high salt concentration (plate on the left in the picture below). The differential ingredient in MSA is the sugar mannitol. …

How is MacConkey agar selective and differential?

This medium is both selective and differential. The selective ingredients are the bile salts and the dye, crystal violet which inhibit the growth of Gram-positive bacteria. The differential ingredient is lactose.

Which types of bacteria should grow in EMB and MacConkey media and which will not?

Note: Red colonies and red precipitate due to acid production as a result of lactose fermentation. Note: Neisseria does not grow on MacConkey. Note: Growth, but no fermentation of lactose. Colorless colonies, medium is slightly yellow due to the increased pH resulting from bacterial digestion of peptone in the medium.

Why does EMB inhibit gram positive?

Selective for Gram negative Organisms Eosin and methylene blue act as indicators to differentiate between Gram negative organisms that ferment lactose and those that do not ferment lactose. … The growth of Gram positive bacteria is generally inhibited on EMB agar because of the toxicity of methlyene blue dye.