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Bioburden and Sterility Testing of Medical Devices

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Bioburden and Sterility Testing of Medical Devices

Medical devices, manufactured and used around the world must be sterile, which means that they have to be free of viable microorganisms. Pharmaceutical testing laboratories carry out bioburden testing of the medical devices by estimating the quantity of microorganisms on the surfaces of medical devices.

Bioburden testing is considered an important process that is required for initial validation of medical devices and also as an on-going process control that is undertaken according to various ISO standards. These international quality systems have laid down the requirements for proper validation and control of sterilization processes and bioburden testing of medical devices. Pharmaceutical testing laboratories ensure that medical devices are free of viable microorganisms, according to international quality systems. Bioburden testing involves the following

  • Sterilization process validation
  • Monitoring of raw materials and packaging
  • Measuring the effectiveness of cleaning procedures
  • Environmental monitoring
  • Control and monitoring of manufacturing processes

Nature of bioburden

It is very important to quantify and understand the nature of bioburden prior to sterilization. Therefore, at the outset pharmaceutical testing laboratories determine the microbiological load on medical devices. The bioburden level on the device is then used to calculate the dose or the sterilization time a device may need. In the case of a medical device, it is quite possible that the microbial extraction procedure may not remove all the microorganisms from the device. This could result in underestimating the actual quantity of the bioburden present. There is a need therefore, to establish a correction factor for the medical device being examined.

Monitoring devices

Microbiological testing labs have to also closely monitor the medical devices because reactions to sterilization can bring about changes due to the differences in microorganism present on or inside devices. These changes in the initial bioburden can cause failure off otherwise validated and well controlled sterilization procedure. As part of a continuous process for quality control, pharmaceutical testing labs also carry out quarterly bioburden testing to determine whether the microbiological load on a device has changed in anyway.

Sterile label

Medical devices cannot be labelled sterile unless the sterilisation process has been used effectively. Therefore, bioburden standards provide for minimizing microbiological contamination of the medical devices prior to sterilization. For this it is important to control raw materials, processes and the environment during manufacturing. This is important because even after meticulously controlling the process, a small quantity of microorganisms can be found on the medical devices before sterilization making them non-sterile. Bacteriostasis and Fungistasis measure whether a device inhibits the growth of bacteria or fungi, which may lead to false negatives during sterility testing.

Sample preparation

Testing labs prepare and test a wide variety of devices which could be as small like needles or very large devices used in hospitals. For large devices a Sample Item Portion (SIP) preparation is sometimes necessary. For SIP testing the device is cut into pieces and the most appropriate parts are tested. Pharmaceutical laboratories therefore, need expertise to use well-developed bioburden testing methods for complex medical devices with multiple components.

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