Liofilchem® Bile Esculin Agar, Liquid

Liofilchem® Bile Esculin Agar is a selective differential culture medium specifically formulated for the isolation and presumptive identification of Group D streptococci, particularly Enterococcus species, from food, pharmaceutical, and water samples. The medium is also widely used for the detection and enumeration of fecal enterococci in water quality testing, in accordance with international microbiological standards including ISO 7899-2 and NCCLS guidelines.

This ready-to-use medium is supplied in glass tubes containing 14 ± 1 mL of agar, allowing convenient inoculation and reliable microbial differentiation. The presence of bile salts provides selectivity by inhibiting most Gram-positive organisms except Group D streptococci, while esculin hydrolysis serves as a differential indicator. Enterococci hydrolyze esculin to produce esculetin, which reacts with ferric ammonium citrate in the medium to form a dark brown or black complex—providing a clear visual confirmation of positive isolates.

Principle of the Medium

Bile Esculin Agar combines selective and differential properties to enable reliable identification:

• Peptone and Tryptone: Provide essential nitrogen, peptides, and amino acids for bacterial growth
• Yeast Extract: Supplies vitamins, especially B-complex vitamins, and additional growth factors
• Oxgall (Bile Salts): Selective agent that inhibits most Gram-positive bacteria except Group D streptococci and enterococci
• Esculin: Differential substrate hydrolyzed by enterococci to produce esculetin
• Ferric Ammonium Citrate: Reacts with esculetin to produce a dark brown or black coloration indicating esculin hydrolysis
• Sodium Chloride: Maintains osmotic balance
• Agar: Solidifying agent providing a stable surface for microbial growth

Positive esculin hydrolysis is indicated by blackening of the medium surrounding bacterial colonies.

Typical Formula (g/L)

Product Specifications

Applications

• Isolation of Group D streptococci (Enterococcus spp.)
• Enumeration of fecal enterococci in water samples
• Microbiological testing of food products
• Pharmaceutical microbiological quality control
• Environmental microbiology and hygiene monitoring
• Clinical microbiology laboratories

Technique

1. Inoculate the medium by streaking the agar surface or slope.
2. Incubate aerobically at 36 ± 1 °C for 18–24 hours.
3. Examine for growth and esculin hydrolysis.

Interpretation of Results

Quality Control Performance

Storage and Handling

• Store at 10–25 °C
• Protect from light
• Do not use after expiration date
• Inspect for contamination or deterioration before use

Key Advantages

• Selective and differential identification of Enterococcus spp.
• Ready-to-use format reduces preparation time
• Clear visual indication of esculin hydrolysis
• Suitable for food, pharmaceutical, clinical, and environmental testing
• Compliant with ISO and international microbiological standards

Liofilchem® Bile Esculin Agar is a reliable, standardized selective differential medium for isolating and identifying Group D streptococci and enterococci. Its bile salt selectivity and esculin hydrolysis detection mechanism provide rapid and accurate presumptive identification, making it an essential tool for microbiological quality control, water testing, clinical diagnostics, and pharmaceutical microbiology laboratories.