Microbio Laboratory

                        ......Complete Microbiology

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Sterility Testing (IP/USP)

All test containers are incubated at specific temperatures for at least 14 days, regardless of whether filtration or direct inoculation test method is used.

Sterility Testing Methods

Direct Inoculation (Immersion)

In the Direct Inoculation method the samples are inoculated directly into tubes or bottles that contain an appropriate medium and are incubated for a period of 14 days.

  •  provides a means of sterility testing for materials that cannot be easily filtered.
  •  bacteriostatic or fungistatic components cannot be removed or adequately neutralized.

Membrane Filtration and Direct Transfer 

The membrane filtration method requires the sample to first pass through a membrane capable of retaining microorganisms. An appropriate amount of rinse fluid is then passed through the filter before transferring the membrane into the two test medium.

 In both test methods the test article or membrane is incubated for 14 days in the test media. The majority of biological samples will be tested using the immersion method. However, for test articles with large volumes in which the entire contents must be tested or if there is a substance within the test article that is known or determined to be bacteriostatic or fungistatic , the membrane filtration method may be required.

  • it can accommodate large volume samples (up to 500 ml); 2) if the test article contains substances that inhibit the growth of microorganisms, rinsing the filter membrane with a
  • suitable rinse agent can remove all or most of these inhibitory substances



Direct Inoculation
Direct Immersion
Membrane Filtration