Importance of Negative and Positive Controls in Microbial Analysis : Pharmaguideline -->

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Importance of Negative and Positive Controls in Microbial Analysis

Negative and positive controls help to find the errors during the microbial analysis of pharmaceutical products.
In microbiology, there two types of test controls, the positive and the negative control. The positive control is an experiment that involves the repetition of the test using working treatment. It is a duplicate experiment which helps the analyst confirms the correctness of the results of a particular test.

On the other hand, a negative control is an experiment in which the microbiologist knows that there will be a negative outcome. In the negative control, the microbiologist does not expect any response. It involves testing the experiment with something that you know will have no effect on it.

Negative and Positive ControlsThis helps the analyst compare the result to a new experiment against an already results that are already known. Negative controls are always used during microbiology testing.

A control test is a part of a well-designed scientific experiment. The controls are used to sterile items used during testing, testing the test environment, analyst handling, and sterile glassware. In case any of the product being tested fails there is no repeat testing done unless the test that was carried is invalid. Negative controls are included during all the testing like the environmental monitoring tests, product testing, water testing and much more.

Test control is one of the basic Pharmacopeia requirements. It helps to differentiate between invalid testing and product failure through observing control test. The test is considered to be invalid when there is growth observed in the control experiment; the test can be repeated for proper investigation.

It is used to test whether there was any mishandling that the analyst might have done during the testing, any problem with the sterilized glassware and items and whether the environment was appropriate during the testing or not. Test controls are significant and should be used during any testing till the completion of any particular test.

In an experiment, the control test is important as it helps the analyst to establish the baseline of his experiment by comparing the results. Without these control tests, the microbiologist will not have anything to compare the results. Microbiologists can identify possible errors and mistakes in the experiment if the control results are not what they expected.

This way the analyst can prove if the method, material and the environment are better or worse than an already existing material, method or environment. The control experiment and the main experiment should not be done at different times, by use of different variable or different locations. The experiments should be carried out simultaneously and in natural settings to get valid results.

These controls are expected to result in a lack of change in a dependent variable to determine if the level of the experiment treatment produces any change in the dependent variable. It helps to prove whether the particular variables can give baseline results.

A control experiment is used to compare the test results. This control does not receive any treatment or test, but the test is simply observed under a natural state. It helps determine whether the results that the analyst gets are dependent upon what he did.

Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
.moc.enilediugamrahp@ofni :liamENeed Help: Ask Question

3 comments: Post Yours! Read Comment Policy ▼

  1. Please give an example of any sterility test along with control test for better understanding....

  2. What positive and negative controls will you use in your assays?


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