R2A Medium (Economy Pack) (without Membrane Filter) is supplied by HiMedia. It contains a pale coloured filter membrane pad of 50mm diameter. R2A Medium is used for the heterotrophic plate count of treated potable water using longer incubation period. It is advisable to store this product between 10-30C. Composition (in gm/L) is as follows:

Casein acid hydrolysate (0.50)

Yeast extract (0.50)

Proteose peptone (0.50)

Dextrose (0.50)

Starch, soluble (0.50)

Dipotassium phosphate (0.30)

Magnesium sulphate (0.02)

Sodium pyruvate (0.30)

Agar (15.00)

DriFilter Membrane Nutrient Pad Medium is ready to use sterile culture media in the form of a 50 mm biological inert absorbent pads impregnated with Plate Count medium, then dried and sterilized in 55 mm petri plate. They eliminate the need of laborious media preparation and autoclaving procedures. The nutrient pads just need to be rewetted with sterile distilled water and are ready to use. Use of nutrient pads allows larger sample volumes to be tested at a time. Interpretation of results is directly by counting the CFUs and also quantifies the microbial load present in the sample. The heterotrophic plate count (HPC), formerly known as the standard plate count is a procedure for estimating the number of live heterotrophic bacteria in water and measuring changes during water treatment, in distribution systems or in swimming pools. R-2A Agar is recommended by APHA for estimating the heterotrophic plate count by the pour plate, spread plate or membrane filter procedure. R-2A Agar is formulated as per Reasoner and Geldreich. Stressed or injured organisms during water treatment are unable to grow on high nutrient media, since the faster growing organisms outgrow the former. Therefore using a low nutrient medium like R-2A Agar incubated for longer incubation periods allows these stressed organisms to grow well.