Asked by: Luanna Reintgens

Asked in category: medical health, infectious diseases

Last Updated: 1st Jul 2024

What is the EMB agar test?

Eosin-methylene blue (EMB), a selective and differential medium, is used to isolate fecal bacteria. Eosin Y is a pH indicator dye that forms a dark purple precipitate at low acid. They also inhibit most Gram positive organisms.

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Hence, EMB is selective and different.

Eosin Methylene Blue (or EMB Agar) is a Selective and Differential Medium. Eosin Y, Methylene Blue and the sugars sucrose and lactose in the medium are responsible for the selective and differential features. It is selective because it promotes certain bacteria growth while inhibiting others.

EMB agar can also be used to detect E coli. EMB agar can be used to detect E coli in water samples. E.coli in the water sample/river indicates possible fecal contamination.

Then, you might also wonder, "What can grow on EMB-agar?"

EMB Agar may not be suitable for some strains of Salmonella or Shigella. EMB Agar can be used to grow gram-positive bacteria such as staphylococci and enterococci. These bacteria will usually form small colonies. Non-pathogenic, non-lactose-fermenting organisms will also grow on this medium.

Is EMB Agar complex or defined?

Answer d. EMB-agar is an example medium that can be used to select, differential, or complex media. Chocolate agar is blood agar that has been heated to release growth factors.

17 Related Question Answers Found

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.

What makes MacConkey Agar 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.

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.

What ingredient makes EMB Agar differential?

Eosin–Methylene Blue (EMB) Agar is a differential medium for the detection of Gram negative enteric bacteria. The medium contains peptone, lactose, sucrose, dipotassium phosphate, eosin and methylene blue dyes.

Does E coli ferment lactose?

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.

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 MSA agar selective or differential?

Mannitol Salt Agar (MSA) is a selective and differential medium. The high concentration of salt (7.5%) selects for members of the genus Staphylococcus, since they can tolerate high saline levels. Organisms from other genera may grow, but they typically grow very weakly.

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.

What Bacteria grows on blood agar?

Blood Agar is used to grow a wide range of pathogens particularly those that are more difficult to grow such as Haemophilus influenzae, Streptococcus pneumoniae and Neisseria species. It is also required to detect and differentiate haemolytic bacteria, especially Streptococcus species.

What type of agar does E coli grow on?

Selective growth media for E. coli

Product No.	Name
70143	Mac Conkey Agar No. 1
19352	Mac Conkey Agar No. 1, Vegitone
94216	MacConkey Agar with Crystal Violet, Sodium Chloride and 0.15 % Bile Salts
M8302	MacConkey Agar with Crystal Violet, Sodium Chloride and 0.15 % Bile Salts

Why is blood agar used?

Blood agar contains general nutrients and 5% sheep blood. It is useful for cultivating fastidious organisms and for determining the hemolytic capabilities of an organism. Some bacteria produce exoenzymes that lyse red blood cells and degrade hemoglobin; these are called hemolysins.

Does E coli grow on EMB agar?

Only gram-negative bacteria grow on EMB agar. Gram-positive bacteria are inhibited by the dyes eosin and methylene blue added to the agar. Because of vigorous fermention of lactose and producion of large quantities of acid, colonies of Escherichia coli appear dark and blue-black with a metallic green sheen.

Why is E coli green on EMB Agar?

On EMB if E. coli is grown it will give a distinctive metallic green sheen (due to the metachromatic properties of the dyes, E. coli movement using flagella, and strong acid end-products of fermentation). Some species of Citrobacter and Enterobacter will also react this way to EMB.

Is E coli gram positive?

Escherichia coli (commonly abbreviated E. coli) is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms (endotherms). Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans.

What media is used for E coli?

LB Media (Luria-Bertani) are common bacterial growth media for Escherichia Coli. Although already described in the fifties in the early days of phage genetics these media are still widely used in molecular biology. The two main components of LB media are Tryptone and Yeast Extract.

Does yeast grow on MacConkey Agar?

MacConkey agar not only selects for Gram-negative organisms by inhibiting Gram-positive organisms and yeast but also differentiates the Gram-negative organisms by lactose fermentation. Lactose ferments will stain pink while the nonlactose ferments will be clear colonies.

How do you make Salmonella Shigella Agar?

Preparation of Salmonella Shigella Agar

Suspend 60.0 grams of Salmonella Shigella Agar in 1000 ml distilled water.
Heat to boiling to dissolve the medium completely.
Do not autoclave.
Mix well and pour into sterile Petri plates.

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