Use of flow cytometry method to detect contaminations of platelet suspensions

In this study, it was aimed to investigate bacterial contamination in apheresis platelet suspensions (APS) by automated blood culture system and flow cytometry method (FCM). 33 spiked APS each using 11 bacterial strains (5 standard strains, 6 clinical isolates), were prepared in three different dilutions (1–10, 10–50, 50-100 cfu/mL), incubated in two different temperatures (35–37 °C and 22–24 °C) and different incubation times (18–96 h) evaluated by FCM. This three different dilutions were also inoculated into special platelet culture bottles (BacT/ALERT® BPA) and loaded into the blood culture system. Additionally 80 APSs routinely prepared in the Transfusion Center were evaluated by both FCM and the blood culture system. Platelets were lysed by freeze-thaw method. All spiked samples were positive with BacT/ALERT® BPA in 12–18 h. In 96 h incubation at 22–24 °C, the presence of bacteria was detected by FCM in all other samples (31/33) except low dilutions (1–10 and 10–100 CFU/ml) of K.pneumoniae standard strain. In the 35–37 °C, the presence of bacteria was detected by FCM in all samples (33/33) after 48 h of incubation. In routine APS one sample detected as positive (Bacillus simplex) with BacT/ALERT® BPA and no positivity was detected by FCM. The freeze-thaw method, which we have optimized for the lysis of platelets, is very practical and can be easily applied. The BacT/ALERT® system has been found to be very sensitive in detecting bacterial contamination in PSs. Flow cytometry method has been found to be successful, fast, easy to use and low cost in detecting bacterial contamination in PSs.