Late sampling for automated culture to extend the platelet shelf life to 5 days in Germany

Bacterial contamination of platelet concentrates (PCs) is still a major challenge in transfusion medicine. Different methodologic concepts and screening strategies have been developed and investigated concerning their usability. We evaluated the feasibility of BacT/ALERT automated culture (BacT/A, bioMérieux) with late sampling after 3 days at the earliest.

Twenty-four bacterial strains isolated from PCs and six relevant strains from reference stocks were spiked into apheresis-derived PCs (10-60 colony-forming units [CFU]/bag). Sampling was performed after 3 days, and bacterial detection was investigated using the two detection methods (BacT/A and BactiFlow [BF], bioMérieux). The maximum time-to-result of BacT/A was set to less than 12 hours.

All medium- or high-pathogenic strains are capable of proliferating to high titers, and 100% of contaminated samples were detected by BF and BacT/A (6 to ≤12 h incubation); lower detection rates of BacT/A were obtained within 6 hours of incubation (≤6 h: 76.2-93.4%). The majority of low-pathogenic isolates are also capable of growing in PCs (89.7%), showing a detection rate of 74.3% for BF versus 54.3% for BacT/A (6 to ≤12 h incubation). BacT/A failed to detect bacteria within 6 hours of incubation. Certainly, a small number of strains did not grow under PC storage conditions and were detectable by BacT/A only with increased detection times.

Late sampling after 3 days at the earliest, combined with reduced BacT/A incubation following the negative-to-date concept, offer an alternative opportunity to extend the shelf life of PCs from 4 to 5 days in Germany. The sensitivity of BacT/A with late sampling is nearly comparable to BF; the time-to-result is considerably longer.