Asked by: Jianxiao Echeuarri
medical health infectious diseases

What makes eosin methylene blue selective?

Last Updated: 5th February, 2020

Eosin Methylene Blue (or EMB) Agar is a Selective & Differential Medium. The selective and differential aspects are due to the dyes Eosin Y and Methylene Blue, and the sugars lactose and sucrose in the medium. It is Selective because it encourages some bacteria to grow while inhibiting others.

Click to see full answer.

In this manner, what ingredient makes eosin methylene blue agar selective?

Eosin methylene blue (EMB, also known as "Levine's formulation") is a selective stain for Gram-negative bacteria. EMB contains dyes that are toxic to Gram-positive bacteria. EMB is the selective and differential medium for coliforms. It is a blend of two stains, eosin and methylene blue in the ratio of 6:1.

Likewise, why does EMB inhibit gram positive? Most bacteria that ferment lactose form colonies on EMB agar that are dark blue to black with a metallic sheen due to precipitation of the dyes by the acid by-products of fermentation. The growth of Gram positive bacteria is generally inhibited on EMB agar because of the toxicity of methlyene blue dye.

Hereof, what is the purpose of eosin and methylene blue dyes in eosin methylene blue agar?

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.

What specific ingredient makes MacConkey agar selective and which ingredient makes it differential?

MacConkey Agar. 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.

Related Question Answers

Chahinaz Evstigneev


How do you make eosin methylene blue agar?

Preparation Instructions
Suspend 36 grams of EMB Agar in 1000 mls of distilled water. Heat to dissolve the medium completely. Dispense and sterilize by autoclaving at 15 lbs. pressure (121 °C) for 15 minutes.

Luciene Mazterreka


What organisms grow on eosin methylene blue agar?

Some strains of Salmonella and Shigella may fail to grow on EMB Agar. Some gram-positive bacteria, such as enterococci, staphylococci, and yeast will grow on this medium and usually form pinpoint colonies. Non-pathogenic, non-lactose-fermenting organisms will also grow on this medium.

Bouchta Fouet


Is TSA selective or differential?

TSA (Trypticase Soy Agar) and NA (Nutrient Agar) are General Purpose Media that are not selective or differential, their purpose is simply to grow many types of bacteria cheaply. If you obtain growth on TSA or NA, but not on a selective or differential media, your results are most likely valid.

Miruna Sanders


What is the difference between EMB agar and MacConkey Agar?

MacConkey Agar Plates
These additives cause the agar to only allow growth of Gram-negative bacteria, while inhibiting the growth of Gram-positive organisms. Eosin Methylene Blue (EMB) agar plates do the same thing but use two dyes, eosin and methylene blue, to differentiate between the bacteria.

Atou Gorst


What types of bacteria are inhibited on MacConkey Agar?

MacConkey's is a selective medium that inhibits the growth of Gram-positive bacteria due to the presence of crystal violet and bile salts. Gram-negative bacteria grow well on MAC.

Leanne Demas


Is MacConkey agar selective or differential?

MacConkey Agar (MAC) is a selective and differential medium designed to isolate and differentiate enterics based on their ability to ferment lactose. Bile salts and crystal violet inhibit the growth of Gram positive organisms. Lactose provides a source of fermentable carbohydrate, allowing for differentiation.

Deshawn Fiallegas


How is eosin methylene blue agar selective and differential?

Eosin Methylene Blue (or EMB) Agar is a Selective & Differential Medium. The selective and differential aspects are due to the dyes Eosin Y and Methylene Blue, and the sugars lactose and sucrose in the medium. It is Selective because it encourages some bacteria to grow while inhibiting others.

Tiantian Irureguigoitia


Is MacConkey Agar defined or complex?

Nutrient broth, tryptic soy broth, and chocolate agar, are all examples of complex media. Selective media are used for the growth of only selected microorganisms. An example of a selective medium is MacConkey agar (Table 9.1 & Figure 9.26).

Bertin Twers


What is MacConkey agar used for?

MacConkey agar is an indicator, a selective and differential culture medium for bacteria designed to selectively isolate Gram-negative and enteric (normally found in the intestinal tract) bacilli and differentiate them based on lactose fermentation.

Immanuel Tabarra


Is blood agar selective or differential?

Blood agar is a differential medium that distinguishes bacterial species by their ability to break down red blood cells. The ability to break down the cells will cause a change in the color of the blood agar. Some media are both differential and selective.



Is E coli a lactose fermenter?

E. coli are facultative anaerobic, Gram-negative bacilli that will ferment lactose to produce hydrogen sulfide. Up to 10% of isolates have historically been reported to be slow or non-lactose fermenting, though clinical differences are unknown.

Alphonso Bartos


Is E coli Gram positive or negative?

Escherichia coli (/ˌ???ˈr?ki? ˈko?la?/), also known as E. coli (/ˌiː ˈko?la?/), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus Escherichia that is commonly found in the lower intestine of warm-blooded organisms (endotherms).

Mildrey Boeschlin


What is the sugar present in EMB Agar?

EMB contains lactose and sucrose sugars, but it is the lactose that is the key to the medium.

Charlesetta Dupont


What is EC broth?

EC Broth (Escherichia coli Broth) is a selective enrichment broth designed for the isolation of coliforms, including E. coli, from water and food samples. It was the recommended medium of the American Public Health Association (APHA) and the AOAC.

Ausra Paeper


How would you recognize a coliform on EMB Agar?

The confirmed test involves taking a sample from a positive lactose broth tube and streaking it onto Eosin Methylene Blue (EMB) agar. The appearance of dark colonies, often with a metallic sheen, indicate a coliform. EMB is a selective and differential medium. It selects for Gram-negative bacteria.

Kostyantyn Argelich


Why can mannitol salt agar and EMB?

Why can mannitol salt agar and EMB agar be described as both selective and differential media? They encourage the growth of both gram negative and gram positive bacteria. Mannitol salt agar is used to isolate staphylococci from clinical and nonclinical samples. EMB agar is used for the detection of E.

Aura Kimig


How does methylene blue inhibit gram positive?

Why does Methylene Blue inhibit gram positive? - Quora. Why does Methylene Blue inhibit gram positive? Methylene blue is a basic redox dye that oxides disulfide/sulfhydryl bonds which are found more frequently in cell walls of Gram Positive bacteria. It can also cause potassium efflux from yeast and some Gram positives

Ambrosia Brudermanns


What does nutrient agar contain?

Nutrient agar is a general purpose medium supporting growth of a wide range of non-fastidious organisms. It typically contains (mass/volume): 0.5% Peptone - this provides organic nitrogen. 0.3% beef extract/yeast extract - the water-soluble content of these contribute vitamins, carbohydrates, nitrogen, and salts.

Dame Bilichenko


Would Removing eosin Y and R methylene blue from EMB alter the mediums sensitivity or specificity?

Would removing eosin Y and.or methylene blue from EMB agar alter the medium's sensitivity or specificity? Both. It would alter the sensitivity because it would alter the growth and it would alter the specificity because it would affect the results of the indicator.