GROUP A BETA STREP AGAR

Cat. no. A72 Group A Beta Strep Agar, 15x100mm Plate, 17ml 10 plates/bag
Cat. no. GA72 Group A Beta Strep Agar, 15x100mm Plate, Reduced Stacking Ring, 17ml 10 plates/bag
Cat. no. J92 Group A Beta Strep Agar / Blood Agar, 15x100mm
Biplate, 10ml/10ml
10 plates/bag

INTENDED USE

Hardy Diagnostics Group A Beta Strep Agar is an enriched media for the selective isolation of group A streptococci ( Streptococcus pyogenes ).

SUMMARY

Group A Beta Strep Agar is a selective media for isolation of group A streptococci (GAS) from respiratory sources. Group A streptococci are virulent pathogens and timely detection, reporting and antibiotic treatment decreases the risk of non-suppurative sequela.

The recovery of group A beta-hemolytic streptococci from throat swabs is a widely applied and well-accepted method. However, problems can occur with routine cultures because overgrowth of normal upper respiratory tract flora will obscure the presence of GAS and result in false-negative results. Additionally, delays in reporting can be caused by attempting to re-isolate the organism. Other formulations using selective agents resulted in inhibition and slow growth rate of the group A streptococci. By utilizing a nutritive growth medium as the base, inhibitory effects of the selective agents on group A streptococci are almost entirely eliminated.

Tryptic Soy Agar is the basal medium for Selective Strep Agar. Organic nitrogen, particularly amino acids and long-chained peptides are supplied by the combination of casein and soy peptones. This combination renders the medium highly nutritious. Osmotic equilibrium is maintained by sodium chloride. Sheep blood (5%) has been added to facilitate growth and to detect hemolytic activity. Selective agents are added to inhibit most other normal respiratory flora including Neisseria spp., most Enterobacteriaceae, diptheroids, Pseudomonas species, and Streptococcus mitis . Streptococcus pneumoniae and streptococci groups C, F, and G are also inhibited.

FORMULA

Ingredients per liter of deionized water:*

Casein Peptone 15.0gm
Soy Peptone 5.0gm
Sodium Chloride 5.0gm
Selective Agents 35.5mg
Sheep Blood 50.0ml
Agar 15.0gm

Final pH 7.3 +/- 0.2 at 25ºC.

* Adjusted and/or supplemented as needed to meet performance requirements.

STORAGE AND SHELF LIFE

Storage: Upon receipt store at 2-8ºC. away from direct light. Media should not be used if there are any signs of deterioration (shrinking, cracking, or discoloration), hemolysis, contamination, or if the expiration date has passed. Product is light and temperature sensitive; protect from light, excessive heat, moisture, and freezing.

PRECAUTIONS

PROCEDURE

Specimen Collection: Infectious material should be submitted directly to the laboratory without delay and protected form excessive heat and cold. If there is to be a delay in processing, specimens should be inoculated into an appropriate transport media and refrigerated until inoculation.

Method of Use: Prior to inoculation, the medium should be brought to room temperature. Inoculate media with specimen and streak for isolation using four quadrant technique. For testing an isolated organism, touch the top of a colony with a sterile wire loop and streak for isolation. Stab the medium several times with the inoculating loop in the area of heavy inoculation in order to create anaerobic conditions to stimulate maximum expression of beta-hemolysis. Incubate aerobically at 35ºC. for 24-48 hours. Plates may also be incubated in 5-10% CO 2 or anaerobically for better development of hemolytic reactions. Examine plate for growth and typical colony morphology and hemolysis.

INTERPRETATION OF RESULTS

Typical colonies of group A streptococci appear small, white, and convex surrounded by a zone of beta-hemolysis after 24-48 hours of incubation. Refer to listed references for more information. (1,2)

LIMITATIONS

Unless a provision is made to reduce oxygen tension, approximately 2% of group A streptococci may be missed if incubated aerobically. It is recommended that several stabs be made into the medium upon inoculation. (1) Incubation in increased CO 2 or anaerobically is recommended.

MATERIALS REQUIRED BUT NOT PROVIDED

Standard microbiological supplies and equipment such as loops, other culture media, swabs, applicator sticks, incinerators, and incubators, etc., as well as serological and biochemical reagents, are not provided.

QUALITY CONTROL

Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Streptococcus pyogenes
ATCC ® 19615
A 24hr 35°C CO 2 ** Growth with beta-hemolysis
Streptococcus mitis
ATCC ® 6249
B 24hr 35°C CO 2 ** Growth; pinpoint colonies, alpha hemolysis
Escherichia coli
ATCC ® 25922
B 24hr 35°C CO 2 ** Partial to complete ihibition
Staphylococcus epidermidis
ATCC ® 12228
B 24hr 35°C CO 2 ** Partial to complete ihibition

** Atmosphere of incubation is enriched with 5-10% CO 2

User Quality Control

PHYSICAL APPEARANCE

Group A Beta Strep Agar should appear opaque, and cherry red in color.

S. pyogenes growing on Group A Beta Strep Agar

Streptococcus pyogenes (ATCC ® 19615) colonies growing on Group A Beta Strep Agar (Cat. no. A72). Incubated in CO 2 for 24 hours at 35ºC.

E. coli inhibited on Group A Beta Strep Agar

Escherichia coli (ATCC ® 25922) growth inhibited on Group A Beta Strep Agar (Cat. no. A72). Incubated aerobically for 24 hours at 35ºC.

REFERENCES

1. Versalovic, J., et al. Manual of Clinical Microbiology. American Society for Microbiology, Washington, D.C.

2. Tille, P., et al. Bailey and Scott's Diagnostic Microbiology, C.V. Mosby Company, St. Louis, MO.

3. Anderson, N.L., et al. Cumitech 3B; Quality Systems in the Clinical Microbiology Laboratory, Coordinating ed., A.S. Weissfeld. American Society for Microbiology, Washington, D.C.

4. Quality Assurance for Commercially Prepared Microbiological Culture Media, M22. Clinical and Laboratory Standards Institute (CLSI - formerly NCCLS), Wayne, PA.


ATCC is a registered trademark of the American Type Culture Collection.

022516gr