Scientists use a number of different methods to determine the number of microorganisms that are present in a given population. This can be accomplished by one of the method which is serial diluting the bacteria and plating the diluted bacteria on media that supports the growth of the micro-organisms. However, the latter method is another method that need more time consuming, but will provide statistically accurate and repeatable results. It is one the ideal method for enumerating microorganisms in a given population because it only study the living organisms in that population. Microbial counting is useful in the basic sciences and is used determine the number of bacteria present for physiological or biochemical studies.
Besides, the ability of microbial counting is to determine the safety of many foods and drugs depends on knowing the levels of microorganisms in those products (Dr. Bassiri E.). We are measuring the number of viable cells in viable plates counts, unlike the microscopic counts which cannot distinguish live from dead cells. It takes some time for the visible colonies to grow. Before doing that, serial dilutions are required and if the sample is serially diluted, single isolated bacteria can form visible isolated colonies.
On top of that, to complete the plate counts, we could either use pour plate method or spread plate method and each of them have their advantages and limitations. All the visible colonies are calculated and represented as colony forming units, CFU. Then, multiplied it with the corresponding dilution factor and the population of original sample will known.