Bioburden

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What is Bioburden, and Why is it Important?

Bioburden is a term used to describe the total number of viable microorganisms on or within a product. Bioburden determinations in drugs, medical devices, and biologics are a cornerstone of sterility testing. Bioburden testing is a must for any manufacturer using gamma or e-beam processes to sterilize products.

Bioburden tests determine the dose of radiation required to sterilize a given drug, biologic, or medical device. Greater doses of radiation are required to kill greater biological burdens on a given product. Therefore, bioburden numbers are used to set initial radiation doses and ensure the process renders the medical devices sterile reliably. Ongoing monitoring of bioburden – meaning testing representative samples from manufacturing for bioburden levels periodically – ensures the dose of radiation for sterilization remains adequate to achieve sterility despite changes over time to manufacturing processes and environments.

Microbiologists refer to the probability a given sterilization process functions as intended as the sterility assurance level (SAL). The industry standard and FDA-required SAL for sterile medical devices, biologics, and drugs is 10⁻⁶. This means that there is less than a one in a million chance that a given sterilized medical device contains a single viable microorganism.

The goal for drug, device, and biologics manufacturers utilizing using irradiation is to keep bioburden levels low and stable to ensure sterility.

What is a Bioburden Test?

A bioburden test removes and quantifies viable microorganisms from a product. A good bioburden test evaluates method suitability by looking for potential microorganism types, potential locations on or in the product, the effect of the test method on any microorganisms present, and the nature of the product being tested. Once the test procedure and basic parameters for a given drug or device have been identified, evaluated, and found suitable, the test is routine and relatively straightforward.

The method of bioburden testing is highly dependent on the material of the product. For example, if the item is completely solid, it would be fully immersed into a liquid (e.g., PBS) and sonicated, followed by membrane filtration and plating. The plates would then be incubated and eventually counted to determine the bioburden.

What standard method is used for bioburden testing?

ISO 11737, is the method most commonly used to evaluate the bioburden of medical devices and pharmaceuticals. The official name of the method is “Sterilization of health care products – Microbiological methods – Part 1: Determination of a population of microorganisms on products.” In the industry, the test is just referred to as bioburden or ISO 11737-1.

When is bioburden testing required?

Bioburden testing is required for any medical device or drug manufacturer using radiation to sterilize a medical device, in order to set the dose, to ensure it achieves a given SAL. In addition, ongoing bioburden testing is required. This bioburden testing is typically conducted quarterly, and is called a quarterly dose audit.

Example: Bioburden Testing of Plastic Syringes to Ensure Sterility

The Challenge

Plastic syringes are an obvious example of where reliable sterilization of a medical device is critical to prevent infections. If the syringes are sterilized with e-beam or gamma radiation, bioburden testing plays a critical role in validation of the sterilization processes as well as ongoing dose monitoring.

The Challenge

During manufacturing, plastic syringes can accumulate microbial contaminants from various sources including the environment, equipment, and human handling. Accurate assessment of this bioburden is essential to establish the correct irradiation dose needed to achieve a sterility assurance level (SAL) of 10⁻⁶, and to ensure the radiation dose remains adequate going forward.

The Process

Sample Collection: Random samples from different production batches are selected to account for variability in contamination levels.

Extraction of Microorganisms: Each syringe is immersed in a sterile solution, such as phosphate-buffered saline (PBS), and subjected to sonication. This process dislodges microorganisms from both external and internal surfaces.

Filtration and Culturing: The resulting solution is filtered through a membrane to capture the microorganisms. The membrane is then placed on a nutrient agar medium and incubated under conditions favorable for microbial growth.

Enumeration: After incubation, colonies that have formed on the agar are counted. These counts provide the total viable microorganism load present on each syringe.

Outcome

The bioburden data obtained enabled calculation of the minimum irradiation dose required for effective sterilization. Implementing rigorous bioburden testing protocols not only complies with international standards, such as ISO 11737-1:2018, but also upholds patient safety by minimizing the risk of infection from contaminated medical devices.

How does Microchem Laboratory approach bioburden testing?

Microchem Laboratory is a well-established microbiology laboratory that has been testing medical devices for decades. We bring unmatched expertise and precision to bioburden testing. Most importantly, our turnaround times are fast and we make it easy to tailor bioburden testing to your company’s particular project. We adhere to international standards like ISO 11737-1:2018, providing our clients with confidence in their sterilization processes. Whether you’re validating a new product or optimizing existing sterilization protocols, Microchem Laboratory is your trusted partner in ensuring safety and compliance. Contact us today for free consultation or a quote.

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