Violet Red Bile Agar (VRBA)

Item No.  NCM0025A

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Violet Red Bile Agar is used for the enumeration of coliforms in food and dairy products in a laboratory setting. Violet Red Bile Agar is not intended for use in the diagnosis of disease or other conditions in humans and conforms to American Public Health Association (APHA).

The coliform group of bacteria includes aerobic and facultative anaerobic, gram-negative, non-spore forming bacilli. Coliforms ferment lactose and form acid and gas at 35°C within 48 hours. Members of Enterobacteriaceae comprise the majority of the group, but other lactose fermenting organisms may also be included.

Procedures to detect, enumerate, and presumptively identify coliforms are used in testing foods and dairy products. One method for performing the presumptive test for coliforms uses Violet Red Bile Agar, (VRBA). If typical coliform colonies appear, they are tested further to confirm their identification as coliforms. Coliform colonies lower the pH of the medium, subsequently causing their colonies to look red (Neutral Red Dye) and to precipitate the bile salts.

Analyte Coliforms, E. coli
Brand NEOGEN® Culture Media
Formula Liter
Yeast Extract 3.0 g/L
Enzymatic Digest of Gelatin 7.0 g/L
Bile Salts 1.5 g/L
Lactose 10.0 g/L
Sodium Chloride 5.0 g/L
Neutral Red 0.03 g/L
Crystal Violet 0.002 g/L
Agar 15.0 g/L
Grams per Litre 41.50
Litres per 500g 12.00
Mass 500 g
Package Dimensions 4.60 IN x 2.90 IN x 8.60 IN
Package Weight 1.35 LB
Plates per 500g 660.00
  1. Suspend 41.5 grams of the medium in one liter of purified water.
  2. Heat with frequent agitation and boil for two minutes. DO NOT AUTOCLAVE.
  3. Cool the medium to 45-50ºC and dispense 15-20 mL into 100 mm petri dishes containing inoculum.
  4. After solidification of the inoculated medium, evenly add a cover layer of 4 mL of the cooled (45-50ºC) agar medium.
Previous Item Number Product was previously known as Acumedia Product: 7165 Violet Red Bile Agar



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