Bioburden testing
Bioburden testing is used to estimate the population of microorganisms on the surfaces of medical devices, empty product vials and bulk products by membrane filtration.
In the case of medical devices, bioburden testing is an important element of the initial process validation and ongoing process control as set out in various ISO standards.
Principle of test
The population of viable microorganisms (bioburden) in a product or on a product surface is required to monitor a production process, either for a medicinal product or a medical device.
This is normally done by microorganism spike/recovery experiments. In the case of medical devices, there is the possibility that the extraction procedure may not remove all the microorganisms from the device, thereby causing an underestimation of the actual bioburden present. It is therefore important to ensure a correction factor for the particular device being studied. There are two approaches that can be used to establish the correction factor, which are based on the ISO standard 11737:1.
For medical devices with a predicted natural bioburden, a repetitive treatment is employed. The device is rinsed with diluent and filtered and repeated multiple times until there are no or very few micro organisms recovered. The number of colonies recovered after initial filter of the removal technique is expressed as a fraction of the total number of colonies counted.
This fraction is then applied as the correction factor for all further testing of that device by that method. The routine result is then expressed as the bioburden estimate, which represents the detected bioburden count multiplied by the correction factor.
For devices with a predicted low bioburden, an inoculation treatment is used. The device is artificially inoculated with a known low number of Bacillus subtilus ATCC 11774.
The inoculated device is then immersed in diluent, massaged, and the rinse filtered. The correction factor is calculated as the proportion of organisms removed compared to the original inoculum applied.
Sample requirements
- Validation: 3 – 5 devices
- Bioburden estimate: 1 device
Get in touch
Would you like to find out more about our testing solutions, or do you need tailored analytical support? Contact us today to get in touch with our experts.