Enterococci · Differentiation
Bile Esculin Agar – differentiation of enterococci and group D streptococci
Bile Esculin Agar is a differential medium for the presumptive identification of enterococci and group D streptococci by their ability to grow in the presence of bile and to hydrolyse esculin.
- Bile tolerance and esculin hydrolysis
- Black or brown colonies and medium
- For colonies from water, food and clinical samples
How Bile Esculin Agar works
Bile inhibits most Gram-positive bacteria other than enterococci and group D streptococci. These hydrolyse esculin, and the esculetin formed reacts with ferric citrate, so the colonies and the surrounding medium turn black or brown.
Typical colony appearance
| Organism | Colonies |
| Enterococcus faecalis | Growth, brown-black halo |
| Escherichia coli | Colourless colonies |
| Staphylococcus aureus | Inhibited |
Technical data
| Preparation | 44.5 g/L; boil to dissolve, autoclave 121 °C 15 min, cool to about 50 °C and pour plates |
| Final pH | 7.1 ± 0.2 |
| Incubation | 35–37 °C, 18–24 h |
| Storage | Dry, dark place; keep the container tightly closed |
| Shelf life | 3 years |
Applications and practical notes
Enterococci and streptococci are tested in drinking, bathing and waste water, in food and in clinical and dairy laboratories, for example according to ISO 7899-2. Typical applications include:
- Drinking, bathing and recreational water
- Waste water and environmental samples
- Food and dairy products
- Clinical and veterinary microbiology
Working with Bile Esculin Agar: Inoculate a pure colony and read the result after 18–24 hours; blackening of at least half of a slant counts as positive.
Good practice with dehydrated media: keep the bottle tightly closed in a cool, dry place, weigh the powder quickly to avoid moisture uptake, and use fresh distilled or deionised water. Check the pH of each new batch after preparation and before use, and label prepared media with the date. Performance of each lot can be verified with reference strains according to ISO 11133, the standard for the preparation, production, storage and performance testing of culture media.
About the Enterococcus methods: intestinal enterococci are indicators of faecal contamination of water. ISO 7899-2 counts them by membrane filtration on Slanetz and Bartley Agar, where typical colonies are red, maroon or pink, and confirms them by transferring the membrane to Bile Esculin Azide Agar, where esculin hydrolysis turns the medium black. In food, enterococci are counted on bile esculin azide media. Streptococci are cultivated on blood agar, where the type of haemolysis is read, and grouped by Lancefield antigens. COLO.Science offers media, supplements, rapid tests and identification kits for these methods.
Complete sets from one supplier: COLO.Science supplies culture media, supplements, rapid tests, identification kits and QC strains as complete sets for the method you follow. Send us your sample types and standards, and we will prepare an offer with the matching products and documentation.
Bile Esculin Agar is supplied by COLO.Science in the pack sizes listed under Ordering information. For larger quantities, regular deliveries or method-specific sets that include Bile Esculin Agar, please send us a request. With every delivery of Bile Esculin Agar you receive the lot number and expiry date, and on request we send the available documentation for Bile Esculin Agar.
Where Bile Esculin Agar fits in Enterococcus and Streptococcus testing
- Enumeration in water – membrane filtration on Slanetz and Bartley Agar
- Confirmation – transfer of the membrane to Bile Esculin Azide Agar; Bile Esculin Agar for single colonies
- Streptococci – Blood Agar Base with blood for haemolysis, Mitis Salivarius Agar with potassium tellurite
- Identification – Lancefield grouping latex, qPCR or LAMP for Enterococcus faecalis
See all Enterococcus and Streptococcus products in the Microbiology Catalogue →
Ordering information
| Product | COLO code | Pack |
|---|---|---|
| Bile Esculin Agar (BEA) | PRO7560 | 500 g |
Product notice: preparation, storage conditions and shelf life are given on the label. Technical data on this page are for orientation; the label and the lot documentation apply. B2B prices are quoted net, excluding VAT.
Sales and technical support
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Quotations and technical support for culture media and microbiology products across our international sales territory. B2B prices are net, excluding VAT.
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Need the complete set for your method?
Send the sample type, target organism and the standard you follow. COLO.Science will put together the media, supplements, QC strains and confirmation tests for the whole procedure.
