CRITERION™ BILE ESCULIN AGAR (BEA)

Cat. no. C5180 CRITERION™ Bile Esculin Agar (BEA) 124gm
Cat. no. C5181 CRITERION™ Bile Esculin Agar (BEA) 500gm
Cat. no. C5182 CRITERION™ Bile Esculin Agar (BEA) 2kg
Cat. no. C5183 CRITERION™ Bile Esculin Agar (BEA) 10kg
Cat. no. C5184 CRITERION™ Bile Esculin Agar (BEA) 50kg

INTENDED USE

Hardy Diagnostics CRITERION™ Bile Esculin Agar (BEA) is recommended for use as a differential medium in the isolation and presumptive identification of enterococci/group D streptococci.

This dehydrated culture medium is a raw material intended to be used in the making of prepared media products, which will require further processing, additional ingredients, or supplements.

SUMMARY

Esculin hydrolysis was first described by Rochaix in 1924.(8) Swan first introduced the use of Bile Esculin Agar in 1954.(9) In 1970, Facklam and Moody determined that the use of the bile esculin test was a reliable way of identifying group D streptococci from non-group D streptococci.(3) When using BEA in biochemical testing of group D streptococci, they found that all group D streptococci will blacken this medium.(3) Other researchers have used BEA for the presumptive identification of Enterobacter spp., Klebsiella spp., and Serratia spp., among the Enterobacteriaceae.

This medium contains esculin, ferric citrate to provide ferric ions, and 4% oxbile to inhibit most other strains of non-group D streptococci. Esculin is hydrolyzed by group D streptococci to form dextrose and esculin. This compound reacts with the ferric ions contained within the medium, turning the medium from its original amber color to a dark brown to black. Thus the tolerance to the presence of bile and the hydrolysis of esculin provide the means to presumptively identify group D streptococci.

FORMULA

Gram weight per liter: 64.0gm/L
Oxbile (Oxgall) 40.0gm
Peptone 5.0gm
Beef Extract 3.0gm
Esculin 1.0gm
Ferric Citrate 0.5gm
Agar 15.0gm

Final pH 6.6 +/- 0.2 at 25ºC.

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

STORAGE AND SHELF LIFE

Store the sealed bottle(s) containing dehydrated culture medium at 2-30ºC. Dehydrated culture medium is very hygroscopic. Keep lid tightly sealed. Protect dehydrated culture media from moisture and light. The dehydrated culture media should be discarded if it is not free-flowing or if the color has changed from its original greenish-beige.

Store the prepared culture media at 2-8ºC.

PRECAUTIONS

METHOD OF PREPARATION FOR DEHYDRATED CULTURE MEDIA

1. Suspend 62.0gm of the dehydrated culture media in 1 liter of distilled or deionized water.

2. Heat to boiling and mix to dissolve completely.

3. Sterilize in the autoclave at 121. for 15 minutes. Heat sensitive. Overheating may cause blackening of media.

4. Cool to 50-55ºC. and aseptically add enrichments (50ml of filter-sterilized horse serum), if desired.

5. Dispense as desired.

PROCEDURE AND INTERPRETATION OF RESULTS

For information on procedures and interpretation of results, consult listed references or refer to the prepared media Instructions for Use (IFU) for Cat. No. G12.

LIMITATIONS

Some strains of Staphylococcus, Aerococcus, and Listeria monocytogenes may grow in the presence of bile and hydrolyze esculin. L. monocytogenes will form minute black colonies.

A heavy inoculum on BEA may cause interpretation of the bile esculin test difficult to read. Excess inoculum decreases the ability of the bile to inhibit growth of other gram-positive organisms that may hydrolyze esculin.

There are a few streptococci that do not hydrolyze esculin but will grow in the presence of bile. Growth without blackening of this medium does not constitute a positive test.

BEA does not contain azide; as a result, gram-negative rods will grow on this medium. Many of these organisms may hydrolyze esculin.

Occasional viridans strains testing Escherichia coli on Bile Esculin Agar or will display reactions that are difficult to interpret. Of the viridans group, 5 to 10% may be able to hydrolyze esculin in the presence of bile.(4)

MATERIALS REQUIRED BUT NOT PROVIDED

Standard microbiological supplies and equipment such as autoclaves, incinerators, and incubators, etc., are not provided.

QUALITY CONTROL

Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Enterococcus faecalis
ATCC® 29212
A 18-48hr 35°C Aerobic Growth; blackening of media around colonies
Streptococcus pyogenes
ATCC® 19615
B 18-48hr 35°C Aerobic Partial to complete inhibition

User Quality Control

PHYSICAL APPEARANCE

CRITERION™ Bile Esculin Agar (BEA) powder should appear homogeneous, free-flowing, and greenish-beige in color. The prepared media should appear slightly opalescent with a bluish-tinge, and greenish to medium amber in color.

REFERENCES

1. Anderson, N.L., et al. Cumitech 3B; Quality Systems in the Clinical Microbiology Laboratory, Coordinating ed., A.S. Weissfeld. American Society for Microbiology, Washington, D.C.

2. Jorgensen., et al. Manual of Clinical Microbiology, American Society for Microbiology, Washington, D.C.

3. Facklam, R.R. and M.D. Moody. 1970. Appl. Microbiol.; 20:245.

4. Tille, P., et al. Bailey and Scott's Diagnostic Microbiology, C.V. Mosby Company, St. Louis, MO.

5. Isenberg, H.D. Clinical Microbiology Procedures Handbook, Vol. I, II & III. American Society for Microbiology, Washington, D.C.

6. Koneman, E.W., et al. Color Atlas and Textbook of Diagnostic Microbiology, J.B. Lippincott Company, Philadelphia, PA.

7. MacFaddin, J.F. 1985. Media for Isolation, Cultivation, Identification, Maintenance of Bacteria, Vol. I. Williams & Wilkins, Baltimore, MD.

8. Quality Assurance for Commercially Prepared Microbiological Culture Media, M22. Clinical and Laboratory Standards Institute (CLSI - formerly NCCLS), Wayne, PA.

9. Rochaix. 1924. Cr. Soc. Biol., Paris; 90:771.

10. Swan, A. 1954. J. Clin. Path.; 7:160-163.


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