Streptococcus Selection Agar

Intended Use

Recommended for selective isolation and enumeration of all types of Streptococci including group A ß-haemolytic strains from clinical samples.

Composition

Final pH (at 25°C): 7.4±0.2

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 45.6 grams in 1000 ml purified / distilled water. Heat to boiling to dissolve the medium completely. Autoclaving is not required if medium is used on the same day. If storage is desired, sterilize by autoclaving at 118°C for 15 minutes. Avoid overheating.

Principle And Interpretation

Streptococcus Selection Agar / Broth is formulated as per Pike (1), for the selective isolation of Streptococci from various materials, especially those which are heavily contaminated with accompanying heterogenous microbial flora (2). Abilities of these media to recover group A ß-haemolytic Streptococci has been reported by Welch et al (3). Tryptone, Soya peptone, dextrose and salts in the medium provide nutrients essential for the growth of Streptococci. Sodium azide and sodium sulphite inhibit gram-negative rods while crystal violet suppresses Staphylococci. However, Streptococci are not affected by these inhibitors at these concentrations. Due to this reason, this media is useful in studies of streptococcal flora from nutritional, dental and epidemiological specimens. Growth of coliforms, Proteus, Pseudomonas and Bacillus species is markedly suppressed in this medium.

However, some strains of Staphylococci and Pneumococci may grow in this medium. All streptococcal colonies must be confirmed for identification.

Type of specimen

Clinical samples - Urine; Water samples

Specimen Collection and Handling

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

For water samples, follow appropriate techniques for sample collection, processing as per guidelines and local standards(4).

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. All presumptive streptococci must be confirmed for 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: Light yellow with purple tinge to light purple coloured clear to slightly opalescent gel forms in Petri plates

Reaction: Reaction of 4.56% w/v aqueous solution at 25°C. pH : 7.4±0.2

pH: 7.20-7.60

Cultural Response: Cultural characteristics observed after an incubation at 35 - 37°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. Pike R. M., 1945, Am. J. Hyg., 41:211.
2. 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.
3. Welch D. F., Henel D., Pickett D., Johnson S., 1991, Am. J. Clin. Pathol., 95:587.
4. Baird R.B., Eaton A.D., and Rice E.W., (Eds.), 2015, Standard Methods for the Examination of Water and Wastewater, 23rd ed., APHA, Washington, D.C.
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