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Radiation Sterilization: Verifying Dose Survivors

Nov 18, 2019 | Medical Device, Microbiology, Technical Expertise

A wealth of knowledge was gained from a historic data review of radiation dose verification failures. Our experts highlight the importance and application of this data set as well as its benefit to device manufacturers.

In last week’s blog post, we highlighted the importance of bioburden monitoring, both quantitatively and qualitatively, as supportive evidence for a valid radiation dose. We arrived at this conclusion through a historic data review of verification dose experiments.

WuXi AppTec Laboratory Testing Division compiled and reviewed 60 randomly selected verification dose experiments performed over a 10-year period that yielded positive sterility results with confirmed genus and species identifications. Testing consisted of a wide range of medical devices, biologics and tissues processed with verification doses ranging from 2.6 to 18.8 kGy.

After exposure to the verification dose, the products were subsequently tested for sterility. Resulting sterility positives from both passing and failed verification dose experiments were identified using biochemical, MALDI TOF MS or DNA sequencing analysis. The data analysis identified the most prevalent survivors and compiled them into a list of top surviving genera.

The top genera were further separated by organism type, such as spore and non-spore formers, and other defining characteristics such as pigmentation to emphasize additional characteristics of survivors:

Survivors from Verification Dose Experiments: Top 8 Genera
Genus Occurrences in 60 Verification Dose Experiments Organism Type Pigmentation of Recovered Isolates
Bacillus 30 (49%) Gram positive spore forming rods Yellow/Cream/Orange
Paenibacillus 12 (20%) Gram positive spore forming rods Cream/White
Deinococcus 9 (15%) Gram positive cocci Pink/Coral
Methylobacterium 9 (15%) Gram negative rods Pink/Coral
Clostridium 6 (10%) Gram positive spore forming rods (obligate anaerobes) Beige/Tan
Roseomonas 6 (10%) Gram negative coccoid rods Pink/Coral
Aureobasidium 2 (3%) Yeast Black
Brevibacillus 2 (3%) Gram positive spore forming rods Tan

Having analyzed data collected over a 10-year period, we have a unique perspective on the types of organisms demonstrating resistance to radiation. This information can be valuable for manufacturers looking to identify adverse trends in viable environmental samples and product bioburden data to prevent costly radiation dose verification failures.

This type of data can be used to evaluate bioburden and the associated manufacturing process. Performing microbial identification and trending of all sterilization dose verification survivors, including passing results, may reveal potential shifts in bioburden types and resistances that might not be apparent with quantitative bioburden data alone.
Clients who work with our microbiology experts are able to leverage the experience we have from testing thousands of devices. Our scientists draw from their previous studies, international standards and current regulatory environment to report results and strategize with our clients when adverse trends occur.

For more information about how you can leverage the knowledge and experience of our microbiology experts for your product testing needs, contact us

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