Detection of the relatively slow-growing Propionibacterium acnes in seven matrices of blood components and advanced therapeutical medicinal products.

Background: Relatively slow-growing bacteria like Propionibacterium acnes represent a challenge for quality control investigations in sterility release testing of blood components and advanced therapeutic medicinal products (ATMPs).

Methods: A convenient validation with 7 matrices was performed using buffy coat, stem cells, islet cells, natural killer cells, red blood cells, platelets and plasma in the microbial detection system Bact/Alert3D incubator. All matrix samples were spiked twofold with Propionibacterium acnes with approximately 50 colony forming units (CFUs) per bottle in iAST and iNST culture bottles for 14days using a multishot bioball. Additionally, the stem cell preparations were also incubated in iFAplus and iFNplus culture bottles, which include neutralizing polymers.

Results: The Bact/Alert3D-System detected Propionibacterium acnes in anaerobic culture bottles in buffy coat [3.3 d (=positive signal day to detection as mean value)], red blood cells [3.2 d], platelets [3.3], plasma [3.7 d], natural killer cells [3.3 d] and islet cells [4.9 d], resp. No growth of Propionibacterium was found in autologous stem cells using iAST and iNST culture bottles. However, Propionibacterium was safely detected in the iFNplus culture bottle with polymers in the stem cell matrix. A successful validation of media was performed.

Conclusions: Our study shows that Bact/Alert3D-System safely detects the relatively slow-growing bacterium Propionibacterium acnes in different matrices in a practical way except stem cells. Using the iFNplus culture bottle for stem cell products positive signals were observed.