Propionibacterium acnes lacks the capability to proliferate in platelet concentrates

Background and Objectives  Propionibacterium acnes is considered to be one of the most frequent contaminants of platelet concentrates (PCs) when anaerobic culture‐based detection methods are used. But Propionibacteria are often detected too late when blood products have already been transfused. Therefore, its transfusion relevance is still demanding clarification because studies of the outcome of patients transfused with P. acnes ‐contaminated PCs are still uncommon. In this study, we monitored clinical effects in patients after transfusion of PCs, which were detected too late in sterility testing. Furthermore, we assessed the bacterial proliferation of Propionibacterium species seeded into PCs to clarify their significance for platelet bacteria screening. Materials and Methods  In the look‐back process, we followed the route of the putative contaminated PC units from storage to transfusion. In the in vitro study, PCs were inoculated with 1–100 colony‐forming unit (CFU)/ml of clinical isolates of Propionibacteria ( n  = 10). Sampling was performed during 10‐day aerobic storage at 22 °C. The presence of bacteria was assessed by plating culture and automated BacT/Alert culture system. Results  Propionibacterium acnes shows slow or no growth under PC storage conditions. Clinical signs of adverse events after transfusion of potentially contaminated PC units were not reported. Conclusion  Propionibacteria do not proliferate under PC storage conditions and therefore may be missed or detected too late when blood products have already been transfused.