LV Agar (Liver Veal Agar)

Intended Use

Recommended for cultivation of fastidious anaerobic organisms.

Composition**

**Formula adjusted, standardized to suit performance parameters

# Equivalent to Liver, infusion from $ Equivalent to Veal, infusion from ## Equivalent to Casein, purified

Directions

Suspend 97.0 grams in 1000 ml warm purified/distilled water. Heat to boiling to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Cool to 45-50°C. Mix well and pour into sterile Petri plates.

Principle And Interpretation

Anaerobic bacteria live in an oxygen-free environment. Some anaerobic bacteria actually die if oxygen is present while others fail to grow and multiply (1). One of the methods of cultivation of anaerobes is using the Sprays medium by using the anaerobic culture dish (2). Liver Veal Agar is formulated as per the medium of Spray (3). Liver Veal Agar is recommended by APHA (4) and the FDA Bacteriological Analytical Manual (BAM) (5). Liver Veal Agar on supplementation of 50% egg yolk is recommended for the cultivation of anaerobic organisms (4,5,6). The medium is highly nutritious and therefore is an excellent medium for growth of sporulating anaerobic bacteria.

HL infusion from, HMV infusion from. Tryptone and gelatin serve as sources of carbon, nitrogen, amino acids and various vitamins. Dextrose serves as the carbon source. Starch enhances growth of anaerobic bacteria. Spray reported isolation of Clostridium perfringens within 6 hours of inoculation and Clostridium tetani within 8 hours. When the medium is inoculated with a small inoculum, gas production is not evident. Spray recommended that the medium should be taken directly from the sterilizer or should be boiled for 10 minutes to drive off dissolved oxygen and cooled without agitation. Serial inoculations are made and the medium is poured into plates. After solidification, 5 ml sterile Liver Veal Agar is poured over the medium as a cover layer to prevent the spreading of surface colonies. Refer standard procedures for isolation and cultivation of anaerobic bacteria (7,8). C. botulinum and C. tetani are highly hazardous and extreme care should be taken while handling these cultures.

Type of specimen

Food and dairy samples Clinical samples - pus

Specimen Collection and Handling

For clinical samples, follow appropriate techniques for sample collection and processing as per guidelines (7,9).

For food and dairy samples, follow appropriate techniques for sample collection and processing as per guidelines (4,10,11).

After use, contaminated materials must be sterilized by autoclaving before discarding.

Warning and Precautions

In Vitro Diagnostic use. For professional use only. 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 clinical specimens. Safety guidelines may be referred in individual safety data sheets.

Limitations

1. Individual organisms differ in their growth requirement and may show variable growth patterns on the medium
2. Each lot of the medium has been tested for the organisms specified on the COA. It is recommended to users to validate the medium for any specific microorganism other than mentioned in the COA based on the user’s unique requirement.

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 Light yellow to brownish yellow homogeneous free flowing powder

Gelling Firm,comparable with 1.5% Agar gel

Colour and Clarity of prepared medium Amber coloured clear to slightly opalescent gel forms in Petri plates, may have slight precipitate.

Reaction Reaction of 9.7% w/v aqueous solution at 25°C. pH : 7.3±0.2

pH 7.10-7.50

Cultural Response Cultural characteristics observed after an incubation at 35-37°C for 18-24 hours (under the atmospheric requirement of organism).

Storage and Shelf Life

Store between 10-30°C in a tightly closed container and the prepared medium at 20-30°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 clinical sample must be decontaminated and disposed of in accordance with current laboratory techniques (7,9).

Reference

1. Alcamo I. E., 2001, Fundamentals of Microbiology, 6th Ed., Jones and Bartlett Publishers
2. Spray R. S., 1930, J. Lab. Clin. Med. 16:203.
3. Spray R. S., 1936, J. Bacteriol., 32:135.
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. U.S. Food and Drug Administration, 1995, Bacteriological Analytical Manual, 8th Ed., AOAC International, Gaithersburg, Md
6. Atlas R. M., 2004, Handbook of Microbiological Media, CRC Press, Boca Raton, Fla.
7. Isenberg, (Ed.), 1992, Clinical Microbiology Procedures Handbook,Vol. I, ASM, Washington, D.C.
8. Murray P. R., Baron J. H., Pfaller M. A., Jorgensen J. H. and Yolken R. H., (Eds.), 2003, Manual of Clinical Microbiology, 8th Ed., American Society for Microbiology, Washington, D.C.
9. 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.
10. American Public Health Association, Standard Methods for the Examination of Dairy Products, 1978, 14th Ed., Washington D.C.
11. Wehr H. M. and Frank J. H., 2004, Standard Methods for the Microbiological Examination of Dairy Products, 17th Ed., APHA Inc., Washington, D.C.