Liofilchem Bile Aesculin Azide Agar

Bile Aesculin Azide Agar is a selective medium specifically formulated for the detection, enumeration, and confirmation of enterococci in water and other environmental samples. The medium is designed to comply with ISO 7899-2 standards, ensuring accuracy and reliability in laboratory testing for water quality and microbiological monitoring.

Key Features

1. Selective for Enterococci
   • Incorporates ox-bile and sodium azide to inhibit non-enterococcal Gram-positive and Gram-negative bacteria, ensuring selective growth of enterococci.
2. Confirmatory Medium
   • Used to confirm red-pink colonies grown on primary isolation media (e.g., Slanetz Bartley Agar) for enterococci by the bile-aesculin reaction.
3. Aesculin Hydrolysis Indicator
   • Enterococci hydrolyze aesculin to produce aesculetin, which reacts with ferric ammonium citrate to form a black-brown complex.
4. Compliance with ISO Standards
   • Meets the requirements of ISO 7899-2 for water quality testing via the membrane filtration method.
5. Versatile Applications
   • Suitable for detecting enterococci in water samples, environmental testing, and other material analyses.
6. Convenient Packaging
   • Available in 100 g, 500 g, and 5 kg formats for laboratory flexibility.

Composition (per liter)

Preparation Instructions

1. Suspend 56.7 g of the powder in 1 liter of distilled or deionized water.
2. Heat to boiling while mixing thoroughly to dissolve the medium completely.
3. Autoclave at 121°C for 15 minutes.
4. Cool to 45–50°C and pour into sterile Petri dishes.
5. Store the prepared plates at 2–8°C and protect from light.

Technique

ISO 7899-2 (Membrane Filtration Method):

1. Filter the water sample through a 0.45 µm membrane filter.
2. Transfer the membrane onto Slanetz Bartley Agar and incubate aerobically at 36 ± 2°C for 40–48 hours.
3. Transfer colonies (red-maroon-pink) from Slanetz Bartley Agar onto Bile Aesculin Azide Agar (preheated to 44°C).
4. Incubate at 44 ± 0.5°C for 2 hours.
5. Interpret Results: Enterococci produce colonies with a tan-black coloration in the surrounding medium due to aesculin hydrolysis.

Alternative Inoculation Methods:

• Spread Plating, Pour Plating, or Direct Streaking.
• Incubate plates at 35 ± 2°C for 18–24 hours.

Interpretation of Results

• Positive Reaction: Blackening of the medium indicates aesculin hydrolysis, confirming the presence of enterococci.

Applications

1. Water Quality Testing
   • Detect and enumerate enterococci in drinking water, wastewater, and environmental samples in compliance with ISO 7899-2.
2. Environmental Monitoring
   • Effective for assessing the microbiological quality of environmental samples.
3. Food and Beverage Testing
   • Used in detecting enterococcal contamination in food materials and beverages.
4. Clinical and Veterinary Microbiology
   • Identifies enterococci in diagnostic samples to monitor contamination or infections.

Advantages

1. Highly Selective
   • Sodium azide inhibits Gram-negative bacteria, and ox-bile suppresses non-enterococcal Gram-positive organisms.
2. Reliable Confirmatory Test
   • Aesculin hydrolysis provides a rapid and clear visual result for enterococcal confirmation.
3. Compliance with Standards
   • Complies with ISO 7899-2, ensuring reliability in regulatory water testing.
4. Versatility
   • Suitable for various sample types (water, food, and environmental materials).
5. Ease of Use
   • Simple preparation and clear interpretation of results for routine laboratory work.

Storage

Precautions

• For professional use only in laboratories by trained personnel.
• Follow biosafety guidelines when handling bacterial cultures.
• Dispose of used media and materials following local and national regulations.

References

1. ISO 7899-2:2000. Detection and enumeration of intestinal enterococci—Membrane filtration method.
2. Facklam R.R. and Moody M. D. (1970). Applied Microbiology, 20:245–250.
3. Slanetz L.W. and Bartley C.H. (1957). Journal of Bacteriology, 74:591–595.
4. Isenberg H.D. and Goldberg D. (1970). Applied Microbiology, 20:433–436.

The Liofilchem Bile Aesculin Azide Agar is a robust and selective medium for detecting enterococci in water and other samples, offering reliable results compliant with ISO standards.