VIOLET RED BILE WITH GLUCOSE AGAR (VRBGA), USP

Cat. no. G178 Violet Red Bile with Glucose Agar, USP, 15x100mm Plate, 18ml 10 plates/bag

INTENDED USE

Hardy Diagnostics Violet Red Bile with Glucose Agar is recommended for the detection and enumeration of Enterobacteriaceae in food and dairy products.

This product is not intended to be used for the diagnosis of human disease.

SUMMARY

Enterobacteriaceae include lactose-fermenting coliform bacteria, non-lactose-fermenting strains of Escherichia coli , and other non-lactose-fermenting species of Salmonella and Shigella involved in food spoilage. Because of their potential contamination of food and dairy products, it is important to detect members of the Enterobacteriaceae , rather than traditional coliform bacteria. (1-4)

All species in the Enterobacteriaceae family ferment glucose. Mossel et al. modified traditional Violet Red Bile Agar, adding glucose, resulting in the formulation now known as Violet Red Bile Glucose Agar. (5-7)

Violet Red Bile with Glucose Agar contains peptones and yeast extract to supply carbon, nitrogen, essential minerals, and B-complex vitamins to stimulate the growth of bacteria. Glucose supplies energy for growth and metabolism. Bile salts and crystal violet inhibit the growth of gram-positive bacteria. Neutral red is added as a pH indicator. Agar is the solidifying agent. Organisms that ferment glucose will produce red to purple colonies with red-purple halos, demonstrating bile precipitation in the presence of neutral red.

FORMULA

Ingredients per liter of deionized water:*

Glucose 10.0gm
Enzymatic Digest of Gelatin 7.0gm
Sodium Chloride 5.0gm
Yeast Extract 3.0gm
Bile Salts 1.5gm
Neutral Red 0.03gm
Crystal Violet 2.0mg
Agar 15.0gm

Final pH 7.4 +/- 0.2 at 25ºC.

* Adjusted and/or supplemented as required to meet performance criteria.

STORAGE AND SHELF LIFE

Storage: Upon receipt store at 2-8ºC. away from direct light. Media should not be used if there are any signs of deterioration (shrinking, cracking, or discoloration), contamination, or if the expiration date has passed. Product is light and temperature sensitive; protect from light, excessive heat, moisture, and freezing.

PRECAUTIONS

PROCEDURE

Consult listed references for information on sample collection and procedures for use. (1-8)

Spread Plate Method:

1. Prepare decimal dilutions in sterile diluent to obtain 30-300 CFU per plate.

2. Aseptically inoculate agar surface with 0.1ml of well mixed diluted sample.

3. Spread the dilution evenly over the surface of the medium.

4. Using a sterile spreader device, distribute the inoculum evenly over the agar surface.

5. Incubate plates aerobically for 48 +/- 2.0 hours at 35ºC.

INTERPRETATION OF RESULTS

Enterobacteriaceae ferment glucose, thereby producing acid by-products, and form red to dark purple colonies surrounded by a reddish zone, or halo, of bile precipitate.

LIMITATIONS

Due to a variation in nutritional requirements, some strains encountered may grow poorly or fail to grow at all on this medium.

MATERIALS REQUIRED BUT NOT PROVIDED

Standard microbiological supplies and equipment such as loops, swabs, spreaders, applicator sticks, other culture media, incinerators, and incubators, etc., as well as serological and biochemical reagents, are not provided.

QUALITY CONTROL

Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Escherichia coli
ATCC ® 8739
J 18-24hr 30-35°C Aerobic Growth; pink to red colonies with bile precipitate
Pseudomonas aeruginosa
ATCC ® 9027
J 18-24hr 30-35°C Aerobic Growth

** Tested in accordance with USP <62>.

USER QUALITY CONTROL

Physical Appearance

Violet Red Bile with Glucose Agar should appear clear, slightly opalescent, and reddish-purple in color.

REFERENCES

1. American Public Health Association. Standard Methods for the Examination of Dairy Products, APHA, Washington, D.C.

2. APHA Technical Committee on Microbiological Methods for Foods. Compendium of Methods for the Microbiological Examination of Foods, APHA, Washington, D.C.

3. Draft Standard Methods for Microbiological Examination of Meat Products. 1977. Part 3: Detection and enumeration of Enterobacteriaceae . BS5393: Part 3, ISO/DIS 5552.

4. Mossel, D.A.A. 1985. Media for Enterobacteriaceae . Int. J. Food. Microbiol. ; 2:27.

5. Mossel, D.A.A., W.H.J. Mengerink, and H.H. Scholts. 1962. Use of a modified MacConkey agar medium for the selective growth and enumeration of Enterobacteriaceae . J. Bacteriol .; 84:381.

6. Mossel, D.A.A., I. Eelderink, M. Koopmans, and F. van Rossem. 1978. Lab Practice ; 27:1049-1050.

7. Mossel, D.A.A., I. Eelderink, M. Koopmans, and F. van Rossem. 1979. Influence of carbon source, bile salts and incubation temperature on recovery of Enterobacteriaceae from food using MacConkey-type agars. J. Food Protect. ; 42:470.

8. The Official Compendia of Standards. USP General Chapter <62> Microbiological Examination of Nonsterile Products: Tests for Specified Microorganisms. USP-NF . United States Pharmacopeial Convention Inc., Rockville, MD.


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