Intended Use
Violet Red Bile Glucose Agar is used for detecting and enumerating Enterobacteriaceae in food and dairy products.
Meets United States Pharmacopeia (USP), European Pharmacopoeia (EP) and Japanese Pharmacopoeia (JP) performance specifications, where applicable.

Summary and Explanation
The Enterobacteriaceae group includes lactose-fermenting coliform bacteria, lactose-nonfermenting strains of E. coli, and lactose-nonfermenting species, such as Salmonella and Shigella.
When examining some foods, it is desirable to detect Enterobacteriaceae rather than the coliform bacteria.
Enterobacteriaceae are glucose-fermenting bacteria. Mossel et a modified lactose-containing Violet Red Bile Agar by adding glucose to improve the recovery of Enterobacteriaceae. Later work by Mossel et al. demonstrated that lactose could be omitted,
resulting in the formulation known as Violet Red Bile Glucose Agar (VRBGA).
Violet Red Bile Glucose Agar is recommended for the detection and enumeration of Enterobacteriaceae in food and dairy products. Violet Red Bile Glucose Agar is also listed in the USP as the recommended solid medium for use in the isolation of bile-tolerant gram-negative bacteria from nonsterile pharmaceutical products.
The Violet Red Bile Glucose Agar formulation is available as a dehydrated culture medium, as prepared plated media, and in Difco™ Hycheck™ Enterobacteriaceae hygiene contact slides.
Hycheck™ Enterobacteriaceae slides are double-sided paddles containing both Violet Red Bile Glucose Agar and Tryptic Soy Agar surfaces for immersing into fluids or for sampling surfaces.

User Quality Control
NOTE: Differences in the Identity Specifications and Cultural Response testing for media offered as both Difco™ and BBL™ brands may reflect differences in the development and testing of media for industrial and clinical applications, per the referenced publications.

Identity Specifications
Difco™ Violet Red Bile Glucose Agar
Dehydrated Appearance: Pink-beige to pink, free-flowing, homogeneous (may contain small dark particles).
Solution: 4.15% solution, soluble in purified water upon boiling. Solution is reddish purple, very slightly to slightly opalescent.
Prepared Appearance: Reddish purple, very slightly to slightly opalescent.
Reaction of 4.15%
Solution at 25°C: pH 7.4 ± 0.2

Principles of the Procedure
Violet Red Bile Glucose Agar contains pancreatic digest of gelatin as a source of carbon, nitrogen, vitamins and minerals. Yeast extract supplies B-complex vitamins which stimulate bacterial growth. Glucose is a carbohydrate. Bile salts and crystal violet
inhibit gram-positive bacteria. Glucose fermenters produce red colonies with red-purple halos (bile precipitation) in the presence of neutral red, a pH indicator. Sodium chloride maintains the osmotic balance. Agar is the solidifying agent.

Formula
Difco™ Violet Red Bile Glucose Agar
Approximate Formula* Per Liter
Yeast Extract : 3.0 g
Pancreatic Digest of Gelatin : 7.0 g
Bile Salts No. 3 : 1.5 g
Glucose : 10.0 g
Sodium Chloride : 5.0 g
Neutral Red : 0.03 g
Crystal Violet : 2.0 mg
Agar : 15.0 g
*Adjusted and/or supplemented as required to meet performance criteria.