The heterotrophic plate count (HPC), formerly known as the standard plate count is a procedure for estimating the numbers of live heterotrophic bacteria in water and measuring the changes during water treatment and distribution or in swimming pools. Different methods namely pour plate method, spread plate method and membrane filter method can be followed to obtain heterotrophic plate count. High Plate Count Agar is recommended by APHA for determining heterotrophic plate count (1). This low nutrient medium is likely to produce higher colony counts than high nutrient media.
Peptic digest of animal tissue and casein provide the necessary nitrogenous compounds for the growth of heterotrophic microorganisms. Metallic salts and dipotassium phosphate together with casein and peptic digest of animal tissue promotes the growth of higher number of microorganisms. Refer appropriate references for standard procedures (1).
Storage and Shelf-life:
Store below 30°C in tightly closed container and prepared medium at 2-8°C. Use before expiry period on the label.
Reference:
1.Eaton A. D., Clesceri L. S., Rice E. W. and Greenberg A. W., (Eds.),2005, Standard Methods for the Examination of Water and Wastewater, 21st Ed., APHA, Washington, D.C.