Define Disadvantages of Using the Plate Counts Method?

1. It takes time, usually 24 hours or more is required to obtain visible colonies.

2. Microbial count obtained depends upon the culture media used for plate counts.

3. It is not a very useful method for actinomycetes and moulds because in plate counts, it is the asexual spores, which are counted.

4. More glassware is needed.

5. Errors in result may arise due to errors in dilution or plating.

6. Results are expressed as counts forming unit per ml (CFU/ml) rather than as number of microbes.  It is so because many microbes are present in chains and clusters and it is difficult to be absolutely certain that each colony has arisen from a single cell.  A colony might be produced from a short segment of a chain or from a bacterial clump.