Semisolid RV Medium w/0.9% Agar

Intended Use

For the enrichment of Salmonellae under high osmotic pressure, low pH and at 43°C with modest nutritional requirements.

Composition

Final pH (at 25°C): 5.2 ± 0.2

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 61.68 grams in 1000 ml purified / distilled water. Heat to boiling to dissolve the medium completely. Dispense in tubes or flasks or as desired. Sterilize by autoclaving at 10 lbs pressure ( 115°C) for 15 minutes.

Principle And Interpretation

Semisolid RV Medium w/0.9% agar can be used for enrichment of Salmonellae from human faeces without pre-enrichment (1,2,3). Similar medias are prescribed for the detection of motile Salmonella species from food and environmental specimens (4).

Soya peptone and yeast extract provides the nitrogenous and carbonaceous substances and other essential growth nutrients. Sodium chloride maintains the osmotic balance. Malachite green and high concentration of magnesium chloride inhibits gram positive bacteria. Potassium phosphate buffers the medium well. This medium is used for enrichment of Salmonella and incubated at 43°C.

Type of specimen

Clinical samples - Faeces; Food samples.

Specimen Collection and Handling

For clinical samples follow appropriate techniques for handling specimens as per established guidelines (5,6).

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

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. The medium should be incubated at 43°C only.
2. Further biochemical identification of organisms is required for confirmation.

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 light blue homogeneous free flowing powder

Gelling: Firm comparable with 0.9% Agar gel.

Colour and Clarity of prepared medium: Blue coloured clear to slightly opalescent gel forms in tubes.

Reaction: Reaction of 6.17% w/v aqueous solution at 25°C. pH : 5.2 ± 0.2

pH: 5.00-5.40

Cultural Response

Cultural characteristics observed after an incubation at 42-43°C for 18 - 24 hours.

Key : (*) Corresponding WDCM numbers.

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 (5,6).

Reference

1. Peterz, M., et al., (1989). J.Appl. Bact. 66,523
2. Van Schothorst, M., et al., (1987). Food Microbiol. 4,11
3. Van Schothorst, M., et al., (1983). J.Appl. Bact.54, 209
4. De Smedt J.M., Balderdijk R., Rappold H. and Lautenschlaeger D., 1986, J. Food Prot., 49:510.
5. Isenberg, H.D. Clinical Microbiology Procedures Handbook. 2nd Edition.
6. 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.
7. 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.