Lactobacillus Selection Agar Base

Intended Use:

Recommended for isolation and enumeration of Lactobacilli from food.

Composition**

Final pH (at 25°C): 5.5±0.2

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 84.73 grams in 1000 ml purified/distilled water containing 1.32 ml glacial acetic acid. Heat with frequent stirring. Heat to boiling for 1-2 minutes to dissolve the medium completely. DO NOT AUTOCLAVE. If storage is necessary, autoclave at A118°C for 15 minutes. Cool to 45-50°C. Mix well and pour into sterile Petri plates. A Corresponds to 12 lbs pressure.

Principle And Interpretation

Lactobacillus Selection Agar is used for isolation and enumeration of Lactobacilli. Rogosa et al (1,2) developed LBS Agar as a selective medium for isolation and enumeration of Lactobacilli from oral, faecal specimens (3), food (4) and dairy products (5). Lactobacillus Selection Medium was demonstrated to be more suitable for growth of lactobacilli than Tomato Juice Medium traditionally used to isolate lactobacilli. Lactobacilli Selection Media can be further enriched by addition of tomato juice (6).

Tryptone, yeast extract and dextrose are the nitrogen and carbon sources. Polysorbate 80 provides fatty acids required for the metabolism of Lactobacilli. Selectivity of the medium is obtained due to the presence of ammonium citrate and sodium acetate. These inhibit the accompanying microbial and fungal flora and also restrict swarming of colonies (7). Addition of acetic acid lowers the pH which is inhibitory to many microorganisms but favours the growth of Lactobacilli. Lactobacillus on this medium appears as large, white colonies. Growth from Lactobacillus Selection HiVeg™ Broth Base (MV1166) can be isolated on Lactobacillus Selection Agar Base. Since these media are highly selective, they should not be used for maintenance of lactobacilli.

Type of specimen

Food and dairy samples.

Specimen Collection and Handling

For food and dairy samples, follow appropriate techniques for sample collection and processing as per guidelines (4,8). After use, contaminated materials must be sterilized by autoclaving before discarding.

Warning and Precautions

Read the label before opening the container. Wear protective gloves/protective clothing/eye protection/face protection. Follow good microbiological lab practices while handling specimens and culture. Standard precautions as per established guidelines should be followed while handling specimens. Safety guidelines may be referred in individual safety data sheets.

Limitations :

• The Bacterias sustaining low pH, may grow on this media.
• Some organisms may show poor growth due to nutritional variations.

Performance and Evaluation

Performance of the medium is expected when used as per the direction on the label within the expiry period when stored at recommended temperature.

Quality Control

Appearance Cream to yellow homogeneous free flowing powder

Gelling Firm, comparable with 1.5% Agar gel

Colour and Clarity of prepared medium Yellow coloured slightly opalescent gel forms in Petri plates

Reaction Reaction of 8.47% w/v aqueous solution at 25°C. pH : 5.5±0.2

pH 5.30-5.70

Cultural Response Cultural characteristics observed in presence of 3-5% Carbon dioxide (CO2) after an incubation at 35-37°C for 48 hours.

Key: (*) Corresponding WDCM numbers.

## Formerly known as Proteus vulgaris $ Formerly known as Lactobacillus plantarum

Storage and Shelf Life

Store dehydrated and the prepared medium at 2-8°C. Use before expiry date on the label. On opening, product should be properly stored dry, after tightly capping the bottle in order to prevent lump formation due to the hygroscopic nature of the product. Improper storage of the product may lead to lump formation. Store in dry ventilated area protected from extremes of temperature and sources of ignition. Seal the container tightly after use. Product performance is best if used within stated expiry period.

Disposal

User must ensure safe disposal by autoclaving and/or incineration of used or unusable preparations of this product. Follow established laboratory procedures in disposing of infectious materials and material that comes into contact with sample must be decontaminated and disposed of in accordance with current laboratory techniques (9,10).

Reference

1. Rogosa, Mitchell and Wiseman, 1951, J. Bacteriol., 62:132.
2. Rogosa, Mitchell and Wiseman, 1951, J. Dental Res., 30:682.
3. Ellis and Sarles, 1958, J. Bacteriol., 75:272.
4. Salfinger Y., and Tortorello M.L. Fifth (Ed.), 2015, Compendium of Methods for the Microbiological Examination of Foods, 5th Ed., American Public Health Association, Washington, D.C.
5. Richardson (Ed.), 1985, Standard Methods for the Examination of Dairy Products, 15th ed., APHA, Washington, D.C.
6. Sabine D. B. and Vaselekos J., 1965, Nature, 206:960.
7. MacFaddin J. F., 1985, Media for Isolation-Cultivation-Identification-Maintenance of Medical Bacteria, Vol. 1, Williams and Wilkins, Baltimore.
8. Wehr H. M. and Frank J. H., 2004, Standard Methods for the Microbiological Examination of Dairy Products, 17th Ed., APHA Inc., Washington, D.C.
9. Isenberg, H.D. Clinical Microbiology Procedures Handbook 2nd Edition.
10. Jorgensen, J.H., Pfaller, M.A., Carroll, K.C., Funke, G., Landry, M.L., Richter, S.S and Warnock., D.W. (2015) Manual of Clinical Microbiology, 11th Edition. Vol. 1.