Listeria Selective Agar (Twin pack)

Intended Use:

Recommended for selective isolation and cultivation of Listeria species from clinical specimens.

Composition**

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 39.0 grams of Part A and 37.5 grams of Part B in 1000 ml 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

Listeria Selective Agar was proposed by Feindt (1) for the cultivation of Listeria species from clinical and non-clinical specimens. Obiger and Schonberg (2) reported the superiority of these media to yield Listeria from mix-infected specimens. Tryptone, Peptone provides essential nutrients. Thiaminium dichloride is the vitamin B source added to improve the growth of Listeria. Thiocyanate and Nalidixic acid inhibits gram-negative bacteria (3,4). Bockemühl (5) reported suppression of Enterococci by combination of selective agents and acridine dyes. The combination of Acriflavin hydrochloride and Nalidixic acid was recommended by Ralovich et al (6) and Kampelmacher and Van Noorle Jansen (7) for the isolation of Listeria. The mix infected specimen is added directly to Listeria Enrichment Broth or subjected to cold enrichment and then cultured on Listeria Selective Agar. Haemolytic forms can be identified by inoculating Blood Agar (M073).

Type of specimen

Clinical samples and Food samples.

Specimen Collection and Handling

For clinical samples follow appropriate techniques for handling specimens as per established guidelines (8,9). For food samples, follow appropriate techniques for sample collection and processing as per guidelines (10). After use, contaminated materials must be sterilized by autoclaving before discarding.

Warning and Precautions :

In Vitro diagnostic Use only. 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 specimens. Safety guidelines may be referred in individual safety data sheets.

Limitations :

1. Some organism may show poor growth due to nutritional variation.

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
Part A : Cream to yellow homogeneous free flowing powder Part B : White to cream homogeneous free flowing powder

Gelling
Firm, comparable with 1.3% Agar gel.

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

Reaction
Reaction of medium (3.9% w/v Part A + 3.75% w/v Part B) at 25°C. pH : 7.4±0.2

pH
7.20-7.60

Cultural Response
Cultural characteristics observed in presence of 10% Carbon dioxide (CO2) after an incubation at 35-37°C for 48 hours.

Key : (*) Corresponding WDCM numbers.

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 clinical sample must be decontaminated and disposed of in accordance with current laboratory techniques (8,9).

Reference

1. Feindt E., 1972, Inuug. Diss., Würzburg.
2. Obiger G. and Schonberg A., 1973, Fleischwirtschaft, 10:1450.
3. Beerens H. and Tahon-Castel M.M., 1966, Ann. Inst. Pasteur, 111:90.
4. Lebnert C., 1964, Arch. Exp. Vet. Med.,8:891 and 1247.
5. Bockemühl J., Seeliger H.P.R. and Kathke R., 1971, J. Med. Microbiol. Imm. 157:84.
6. Ralorich B., et al, 1971, Zbl. Bakt. I.Orig., 216:88.
7. Kampelmacher E.H. and Van Noorle-Jansen L.M., 1972, Zbl. Bakt. J.Orig.,221:139.
8. Isenberg, H.D. Clinical Microbiology Procedures Handbook 2nd Edition
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. 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.