Define Disadvantages of Direct Microscopic Count?
1. Small cells are difficult to see under the microscope and may be missed.
2. It gives total count, i.e., both live and dead cells as it is difficult to distinguish between the two.
3.High concentration of microbes, i.e., about 10 million bacteria/ml is required as very small volume of microbes is sampled.The method is not sensitive to populations of fewer than 1 million.
4. Motile cells must be immobilized before counting.
5. Phase contrast microscope is needed for unstained cells.