ß-Streptococcus Selective Agar Base

Intended Use

Recommended for the isolation of beta-haemolytic Streptococci from clinical specimens heavily contaminated with other bacteria.

Composition**

Final pH (at 25°C): 7.3±0.2

**Formula adjusted, standardized to suit performance parameters

# Equivalent to Meat peptone

$ Equivalent to Meat extract

Directions

Suspend 25.12 grams 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 and add 7-10% sheep blood. Mix well and pour into sterile Petri plates.

Principle And Interpretation

The majority of β-haemolytic streptococci causing infections in man belong to group A and are given the species name of Streptococcus pyogenes. This pathogen causes a variety of inflammatory and suppurative conditions such as sore throat, scarlet fever, cellulites, wound infections, erysipelas, impetigo, puerperal fever, otitis media, septicemia and necrotizing fasciitis. It is also found in the throat or nasal cavity (2). β-Streptococcus Selective Agar Base was described by Liebermeister and Braveny (1,5) for isolating β-haemolytic streptococci. This medium proves to be a nutritionally limiting medium for the accompanying flora, so that their growth is markedly reduced. β-haemolytic streptococci also show reduced colony size but exhibit distinct β-haemolysis. This medium gives higher yields of β-haemolytic streptococci than the regularly used blood agar. The β-haemolysis of streptococci, producing a greenish discoloration is restricted on this medium. Yeast extract and lysine promote the haemolytic action of β-haemolytic streptococci (1, 6). HM peptone and HM extract serve as sources of carbon, nitrogen and essential growth factors. Sodium chloride maintains the osmotic equilibrium of the medium whereas disodium hydrogen phosphate buffers the medium.

Type of specimen

Clinical samples

Specimen Collection and Handling

For clinical samples follow appropriate techniques for handling specimens as per established guidelines (3,4). 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 clinical specimens. Safety guidelines may be referred in individual safety data sheets.

Limitations

1. Further biochemical and serological tests must be carried out for further identification.

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: Basal medium yields light amber coloured clear to slightly oplalescent gel. On addition of 7-10% v/v sterile sheep blood cherry red coloured opaque gel forms in Petri plates.

Reaction: Reaction of 2.5% w/v aqueous solution at 25°C. pH : 7.3±0.2

pH: 7.10-7.80

Cultural Response

Cultural characteristics observed after an incubation at 35-37°C for 18-48 hours with added 7-10% v/v sterile defibrinated blood.

Key : *Corresponding WDCM numbers.

Storage and Shelf Life

Store between 10-30°C in a tightly closed container 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 (3,4).

Reference

1. Bernheimer A. W., Rodbart M., 1948, J. Exp. Med, 88; 149
2. Collee J. G., Fraser A. G., Marmion B. P., Simmons A., (Eds.), Mackie and McCartney, Practical Medical Microbiology, 14th Edition, 1996, Churchill Livingstone.
3. Isenberg, H.D. Clinical Microbiology Procedures Handbook 2nd Edition.
4. 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.
5. Liebermeister K., Braveny J., 1971 Z. med. Mikrobiol. u. Immunol, 156, 149 -1534.
6. Okamoto H., Kyoda S., Ito R., 1939, Jap. J. Med. Sci, VI Pharmacol, 12, 167.