All manufacturers of medical devices should perform routine, random bioburden testing. The appropriate frequency and number of samples varies depending upon the sterility assurance level [SAL], type of product, type of sterilization used, environmental control, and the process controls of the manufacturer.
The AAMI Radiation Sterilization guideline (AAMI/ANSI/ISO 11137) mandates testing ten samples for bioburden with each quarterly audit. Products sterilized by radiation for shipment to many countries in Europe must be dosed based on the actual bioburden for that lot. Manufacturers pursuing the use of radiation sterilization for products for shipment to Japan must perform routine environmental and product bioburden tests and identify the isolates.
The type and frequency of bioburden tests performed on products validated using the AAMI Industrial Ethylene Oxide Sterilization Guideline (AAMI/ANSI/ISO 11135) will also vary with the method used in the initial validation. Products validated using the absolute bioburden method require frequent and significant bioburden testing. Even products validated with the BI overkill method should be tested periodically (at least quarterly) for bioburden.
Bioburden tests may include aerobic bacteria, spores, aerobic fungi, and anaerobes. Many factors enter into the choice of the type of tests most appropriate for your device. Generally, at least the aerobic bacteria and fungi should be counted.
“The service provided by Nelson Labs is exemplary. The Study Directors, Study coordinators, lab technicians, and accounts receivables personnel are friendly, very helpful, and provide timely response. When I have biocompatibility questions or need to schedule testing, Nelson Labs is first on my list of whom to go to.”
Clay , Safety & Compliance Engineer , Medical Device Manufacturer
The method of obtaining samples for either bioburden or sterility tests might influence the test results observed. The preferred method for evaluating products or processes is to obtain random samples. These samples may be selected from routine production which should include products produced at different times during the production of a single lot. The production lot selected to be sampled needs to be representative of typical processing and conditions. Samples may be obtained from in-process rejected materials if those materials have been subjected to the same processing conditions used for the remainder of the lot.
Be as clean as possible when sampling. Samples for sterility testing should be double bagged before they are sent to be dosed. This provides an extra sterile barrier to take into the clean room and can cut down on the number of false positives.
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- Taylor, Program Manager, Medical Device Manufacturer