STANDARD METHODS AGAR

Cat. no. G13 Standard Methods Agar, 15x100mm Plate, with lid label, 18ml 10 plates/bag
Cat. no. G43 Standard Methods Agar, 15x100mm Plate, 18ml 10 plates/bag
Cat. no. G44 Standard Methods Agar, 15x100mm Plate, without label, 18ml 10 plates/bag
Cat. no. H53 Standard Methods Agar, 15x150mm Plate, 68ml 10 plates/bag
Cat. no. Q21 Standard Methods Agar, 20x125mm Tube, 18ml Deep 20 tubes/box
Cat. no. U95 Standard Methods Agar, 4oz. Glass Bottle, 100ml 20 bottles/box
Cat. no. U295 Standard Methods Agar, 8oz. Glass Bottle, 200ml 12 bottles/box
Cat. no. U297 Standard Methods Agar, 500ml Polycarbonate Bottle, 500ml 12 bottles/box
Cat. no. U395 Standard Methods Agar, 16oz. Glass Bottle, 400ml 12 bottles/box

INTENDED USE

Hardy Diagnostics Standard Methods Agar is recommended for use in determining the microbial content in dairy products, food, water samples, and other material of sanitary importance.

This product is not intended to be used for the diagnosis of human disease.

SUMMARY

Standard Methods Agar is a modified formulation of Tryptone Glucose Skim Milk Agar that was developed by Bowers and Hucker. (5) Yale showed that this modified version is more effective in plate count procedures on milk and dairy products.

Standard Methods Agar is equivalent to the formulation of Plate Count Agar (Tryptone Glucose Yeast Agar) as listed in Standard Methods for the Examination of Water and Wastewater , 19th ed., AOAC, and USP. (1-4) The American Public Health Association (APHA) recommends use of the medium for performing the "standard plate count" on dairy products. (6)

Bacterial growth nutrients are provided by peptone, yeast extract, and glucose. B-complex vitamins are primarily supplied by yeast extracts. Glucose serves as an energy source. These nutrients, together with the nutrient factors present in the dairy products to be evaluated will support the growth of the majority of organisms found in the dairy samples.

FORMULA

Ingredients per liter of deionized water:*

Pancreatic Digest of Casein 5.0gm
Yeast Extract 2.5gm
Glucose 1.0gm
Agar 15.0gm

Final pH 7.0 ± 0.2 at 25ºC.

* Adjusted and/or supplemented as required to meet performance criteria.

STORAGE AND SHELF LIFE

Storage: Upon receipt store plated media at 2-8ºC. away from direct light. Tubed and/or bottled media should be stored at 2-30ºC. away from direct light. Media should not be used if there are any signs of deterioration (shrinking, cracking, or discoloration), 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: Consult listed references for information on specimen collection and processing of food, dairy, water samples, and other materials of sanitary significance. (1-8)

Prior to inoculation, warm prepared media to room temperature.

For melting bottled media: Autoclave at 121ºC. for one to three minutes or until melted. Alternatively, a covered, boiling waterbath (100ºC.) can be used. There should be enough water in the waterbath to reach the media line. A covered waterbath will help to reach and maintain the temperature. Heat in waterbath until melted.

Spread Plate Method:

1. Prepare decimal dilutions in sterile diluent to obtain 30-300 CFU per plate.

2. Aseptically inoculate agar surface with 0.1ml of well mixed diluted sample.

3. Using a sterile spreader device, spread the dilution evenly over the surface of the agar.

4. Incubate plates aerobically for 48 +/- 2 hours at 35ºC.

Pour Plate Method:

1. Melt agar by placing in a boiling waterbath until liquified.

2. Cool media to 45-50ºC. Maintain in a 45-50º waterbath until ready to pour.

3. Prepare decimal dilutions in sterile diluent to obtain 30-300 CFU per plate.

4. Place a 1ml inoculation into a sterile petri plate.

5. Aseptically pour approximately 18ml of the cooled media (45-50ºC.) over the inoculum. Carefully swirl the plate to mix the inoculum evenly.

Note: After autoclaving, do not heat media longer than three hours at 45-50ºC. Sterile solidified medium can only be remelted once.

6. Allow media to solidify.

7. Incubate plates aerobically for 48 +/- 2 hours at 35ºC.

INTERPRETATION OF RESULTS

Following incubation, examine the plates for growth. Count the number of colonies and express in number of colony forming units (CFU) per gram or milliliter of sample; take into account the dilution factor. If duplicate plates were set-up, express the average for the two plates in terms of the number of microorganisms per gram or milliliter of sample. Consult listed references for additional information on interpretation and enumeration of microbial growth on this medium. (1-8)

Precipitated zones of para-casein are indicated by white to off-white zones surrounding colonies. Transparent inner zones surrounding white zones indicate digestion of para-caseinate. The presence of caseolytic microorganisms are indicated by either of these reactions.

LIMITATIONS

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
Staphylococcus epidermidis
ATCC ® 12228
A 24hr 35°C Aerobic Growth
Escherichia coli
ATCC ® 25922
A 24hr 35°C Aerobic Growth
Enterococcus faecalis
ATCC ® 29212
A 24hr 35°C Aerobic Growth

User Quality Control

Physical Appearance

Standard Methods Agar should appear slightly opalescent, and light amber in color.

S. epidermidis growing on Standard Methods Agar

Staphylococcus epidermidis (ATCC ® 12228) colonies growing on Standard Methods Agar (Cat. no. G43). Incubated aerobically for 24 hours at 35ºC.

E. coli growing on Standard Methods Agar

Escherichia coli (ATCC ® 25922) colonies growing on Standard Methods Agar (Cat. no. G43). Incubated aerobically for 24 hours at 35ºC.

E. faecalis growing on Standard Methods Agar

Enterococcus faecalis (ATCC ® 29212) colonies growing on Standard Methods Agar (Cat. no. G43). Incubated aerobically for 24 hours at 35ºC.

Standard Methods Agar

Uninoculated plate of Standard Methods Agar (Cat. no. G43).

REFERENCES

1. American Public Health Association. Standard Methods for the Examination of Water and Wastewater, APHA, Washington, D.C.

2. Association of Official Agricultural Chemists, 10th ed. p. 737; 1965.

3. Association of Official Analytical Chemists. Official Methods of Analysis sm , AOAC, Washington, D.C.

4. United States Pharmacopoeia and National Formulary (USP-NF). Rockville, MD: United States Pharmacopeial Convention.

5. Bowers and Hucker. 1944. Tech. Bull ., p. 228. N.Y. State Exp. Station.

6. American Public Health Association. Standard Methods for the Examination of Dairy Products, APHA, Washington, D.C.

7. APHA Technical Committee on Microbiological Methods for Foods. Compendium of Methods for the Microbiological Examination of Foods, APHA, Washington, D.C.

8. U.S. Food and Drug Administration. Bacteriological Analytical Manual. AOAC, Arlington, VA.
http://www.fda.gov/Food/FoodScienceResearch/LaboratoryMethods/ucm2006949.htm.

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

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