Use of Microbial Enzymes in Sterility Testing

USE OF MICROBIAL ENZYMES IN STERILITY TESTING

Sterile pharmaceutical preparations must be tested for the presence of fungal and bacterial contamination before use. Of course if the preparation contains an antibiotic it must be removed or inactivated and this is generally achieved by membrane filtration. However, the technique has certain disadvantages including accidental contamination and retention of the antibiotic on the filter followed by subsequent liberation into the nutrient medium.

Enzymatic inactivation of the antibiotic before testing would provide an elegant solution to this problem. Currently, the only pharmacopoeial method permitted is that of using an appropriate βlactamase to inactivate penicillins and cephalosporins. Other antibiotics that are susceptible to inactivating enzymes are chloramphenicol (by chloramphenicol acetyltransferase) and the aminoglycosides, e.g. gentamicin, which can be inactivated by phosphorylation, acetylation or adenylylation. A method for acetylating and consequently inactivating aminoglycosides prior to testing using 3-N-acetyltransferase (an enzyme with wide substrate specificity) in combination with acetyl coenzyme A has been described, but this method has yet to be adopted.