Repeatability of microbial count

Same analyst same sample analysis method everything are same but every time i get different results.
i test API product (iron sucrose) by membrane filtration technique.
help me what should i do???

This descripency in microbiological testing needs to be carefully investigated. The techniques used by the analysts should be closely supervised by the senior microbiologist right from sample preparation. This also requires adequate training to the microbiologist on how to handle samples and follow the procedure accurately and precisely.
There are chances of variability in the results obtained in microbiological methods, however it should be within limits.