Sterility testing is necessary for pharmaceuticals and medical devices that claim to be sterile or free from viable microorganisms. Sterility testing methods are required to be accurate and reproducible, in accordance with 21CFR 211.194 and 211.165. USP Chapter <71> Sterility Test is the principal source used for sterility testing of sterile drug products produced by aseptic processing. The quantity and number of products to be tested is determined both by batch size and individual container fill volumes. It is important that the samples represent the entire batch and processing conditions. Samples should be taken at the beginning, middle, and end of the aseptic processing operation.
The test evaluates samples for sterility by transferring the solution into growth media, incubating for a minimum of 14 days and then checking for evidence of microbial contamination. To optimize aseptic transfer of samples into the test media, all testing is performed in a state-of-the-art ISO Class 5 cleanroom.
Samples may be tested using either a direct transfer or membrane filtration method using a soybean casein digest broth (SCDB) and fluid thioglycollate media (FTM). Samples tested by direct transfer are aseptically immersed in the test media. Samples tested by membrane filtration are passed through a 0.45µm filter, and the filter is immersed in the test media. SCDB is used for aerobic and fungal growth at incubation temperatures of 20 – 25°C and FTM is used for anaerobic growth at an incubation temperature of 30 – 35°C.
The successful completion of a USP sterility test does not assure that all products in a sterilization lot are sterile. This is accomplished primarily by validation of the sterilization process or of the aseptic processing procedure which, along with the use of routine controls and monitoring, forms the foundation of a sterility assurance program.
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