Bacterial enumeration using Pour Plate Technique

What is Pour Plate Method?

The pour plate method is a microbiological laboratory technique for isolating and counting the viable microorganisms present in a liquid sample, which is added along with or before molten agar medium prior to its solidification.

This technique is generally used to count viable microorganisms in the given sample by enumerating the total number of colony-forming units (CFUs) within and/or on the surface of the solid medium. It is mostly used for enumerating bacteria; however, Actinobacteria, molds, and yeasts can also be isolated and enumerated.

Principle of Pour Plate Meth

The pour Plate Method is based on the fact that when an agar medium mixed with microorganisms is incubated, each of the viable microorganisms will multiply forming a separate colony. In this method, a certain volume, usually 1 mL, of the serially diluted liquid sample is mixed properly with approximately 15 mL of specific molten agar medium of about 40 – 45°C (less than 50°C) in a Petri plate. The medium is allowed to solidify and is incubated, usually at 37°C for 24 – 48 hours. Following the incubation, the viable microorganisms in the sample will grow into visible colonies on the surface of and within the medium. The visible colonies can be counted and CFU/mL can be calculated using the following formula

Total number of colonies obtained X dilution factor == CFU/ml

Volume of specimen used