Violet Red Bile Agar. M Violet Red Bile Agar is selective medium used for the isolation, detection and enumeration of coli-aerogenes bacteria in water, milk. Violet Red Bile Agar (VRB Agar). APHA / COMPF / IDF-FIL / ISO Medium for the detection and enumeration of coliforms in milk and other dairy products. Violet Red Bile Agar is used for the enumeration of coliforms in food and the presumptive test for coliforms uses Violet Red Bile Agar, (VRBA).

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Surface colonies of Escherichia coli appear as entire-edged colonies, while deep colonies appear lens-shaped.

Non-lactose-fermenting microorganisms result in colorless colonies. Consult listed references for information on sample collection. American Public Health Association.

Hardy Diagnostics Violet Red Bile Agar is recommended for the detection of coliforms in food or dairy products. A covered waterbath will help to reach and maintain the temperature. There should be enough water in the waterbath to reach the media line.


Growth; pink to red colonies, may have a slight precipitate around colonies colonies. Heat in waterbath until melted. Non-lactose-fermenting microorganisms produce colorless colonies. Violet Red Bile Agar is a selective medium used to detect and enumerate lactose-fermenting coliform microorganisms.


Experimental Results: Experiment 4

Using a sterile spreader device, distribute the inoculum evenly over the agar surface. Colonies of Enterobacter aerogenes often appear mucoid and pinkish in color. Melt agar by placing in a boiling waterbath until liquified. The medium contains bile salts and crystal violet which serve as inhibitory agents toward some gram-positive microorganisms, especially staphylococci.

Violet Red Bile Agar (VRB Agar)

Spread the dilution evenly over the surface of the medium. Allow medium to warm to room temperature prior to inoculation. Place a 1ml inoculation into a sterile petri plate. Alternatively, a covered, boiling waterbath degrees C.

U Violet Red Bile Agar, 8oz. Enterococci may grow, and if so, usually appear pinpoint in size and rose colored.

Aseptically inoculate agar surface with 0. Lactose-fermenting microorganisms produce pink to red colonies that are generally surrounded by a reddish zone of precipitated bile. Neutral red is employed as the pH indicator.

Consult listed references vrg information concerning inoculation procedures. Product is light and temperature sensitive; protect from light, excessive heat, moisture, and freezing.

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For melting bottled media: Media should not be used if there are any signs of deterioration shrinking, cracking, or discolorationcontamination, or if the expiration date has passed.


Carefully swirl the plate to mix the inoculum evenly. Violet Red Bile Agar contains a low concentration of bile salts, and therefore is not completely specific for enterics. This product is not intended to be used for the diagnosis of human disease.

Violet Red Bile (VRB) Agar – for the detection of coliforms

Lactose-fermenting microorganisms, including coliforms, produce pink to red colonies that are generally surrounded by a reddish zone of precipitated bile. Prepare decimal dilutions in sterile diluent to obtain CFU per plate. Standard microbiological supplies and equipment such as loops, slides, staining supplies, Lauryl Sulfate Broth, other culture media, microscopes, incinerators, and incubators, etc.

The medium is recommended for use in the microbiological analysis of milk and other dairy products, and for use in the examination of water.