Sterility testing accidental contamination

Sterile pharmaceutical preparations must be tested for the presence of fungal and bacterial contamination before use (see Chapters 18 and 23). If the preparation contains an antibiotic, it must be removed or inactivated. Membrane filtration is the usual recommended method. However, this technique has certain disadvantages. Accidental contamination is a problem, as is the retention of the antibiotic on the filter and its subsequent liberation into the nutrient medium. 

If microbial growth is detected in a sterility test, this may reflect a falsepositive reading because of the problem of accidental contamination of the culture media while performing the sterility test. The problem of accidental contamination is a serious yet unavoidable limitation of the sterility test. 

Tests for sterility are to be carried out by trained personnel using techniques and equipment that minimize the risks of accidental microbial contamination of the tests and of the testing environment. 

It is essential that all tests for sterility should be carried out under the most strictly aseptic conditions, in order to eliminate contamination from sources other than the actual material being tested. Otherwise, it is quite possible that a batch of material that is, in fact, satisfactory might be rejected because of the accidental introduction of a contaminating organism from the air, or from an operator, while the test is being made. 

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