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Thermo Scentific

Dehydrated Culture Media


Code: CM0325

A medium for the enumeration of viable organisms in food, animal feed and water samples

Typical Formula*




Yeast extract






pH 7.0 ± 0.2 @ 25°C

* Adjusted as required to meet performance standards

Add 17.5g to 1 litre of distilled water. Dissolve by bringing to the boil with frequent stirring, mix and distribute into final containers. Sterilise by autoclaving at 121°C for 15 minutes.

Plate Count Agar is equivalent to the medium recommended by the APHA1, PHLS 2 and ISO3,4 for the plate count of micro-organisms in food.
The APHA method consists of the preparation of pour plates using diluted samples, and counting colonies after incubation. Incubation is for 48 hours at 32°C or at 35°C for the Standard Plate Count. For the enumeration of micro-organisms with other temperature requirements, plates may also be incubated for 7-10 days at 5-7°C: for 3-5 days at 20°C; for 2-3 days at 45°C; or for 48 hours at 55°C. See the APHA1 publication for details.

Samples should be tested following the method described in the appropriate standard.

The quality control of Plate Count Agar includes testing in accordance with ISO 11133:20145.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared plates at 2-8°C.

Dehydrated medium: Straw coloured, free-flowing powder
Prepared medium: Straw coloured gel

Quality control

Positive controls:

Expected results

Escherichia coli ATCC® 25922 *
Good growth; straw coloured colonies
Bacillus subtilis ATCC® 6633*
Good growth; straw coloured colonies
Staphylococcus aureus ATCC® 25923*
Good growth; straw coloured colonies
Negative control:  
Uninoculated medium No change
* This organism is available as a Culti-Loop®

Quality Control
Compare with previous lot/batch using pasteurised and raw milk samples, incubated at 32-35°C for 48 hours.

Ensure that the procedures and media used in milk product testing comply with the National Regulations required for each country.

1. American Public Health Association (1978) Standard Methods for the Examination of Dairy Products. 14th Edn. APHA Inc. Washington DC.
2. PHLS Standard methods for the Microbial Examination of Food and Dairy Samples (1999) Aerobic plate count at 30°C - F10 & F11
3. International Organization for Standardization. ISO 4833 Parts 1 and 2, Microbiology of the food chain - Horizontal method for the enumeration of microorganisms
4. International Organization for Standardization. Microbiology of food and animal feeding stuffs -- Horizontal method for the enumeration of psychrotrophic microorganisms.
5. International Organization for Standardization. ISO 11133:2014 Microbiology of food, animal feed and water - Preparation, production, storage and performance testing of culture media

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