Bacterial contamination of platelets is considered as the most frequent infectious risk of transfusion. The prevalence of bacterial contamination has been reported and varied considerably in different countries, but the data for bacterial contamination of platelets in China are rarely reported. Eight thousand apheresis platelet concentrates (PCs) were analysed by aerobic and anaerobic cultures. Ten millilitres of PCs were inoculated into aerobic and anaerobic bottles (5 mL each), followed by the incubation for a maximum of 7 days. A new sample was taken from the unit for reculturing in order to confirm the initial positive reaction. All positive culture bottles were referred for bacterial isolation and identification. Twenty one cultures (0.26%) were flagged as positive in initial culture. Five cultures (0.06%) were confirmed as true positive and nine cultures (0.11%) were confirmed as indeterminate in reculture. A bacterium from skin flora (Propionibacterium spp.) was the most prevalent contaminant. Mean time to initial positive culture from start of incubation was 22.1 h for confirmed positive units and 97.3 h for indeterminate units. Most PC units had already been issued by the time of initial positive culture with a 'negative-to-date' issued strategy. There is a risk of bacterial contamination of PCs in China. Implementing bacterial screening of platelets could reduce the risk of septic reaction and fatalities due to transfusion of bacterially contaminated platelets. However, bacterial contamination PCs can still be transfused due to the delay until a positive signal in the culture system.

Our study demonstrates the predominant organisms implicated in CB microbial contamination were part of the human intestinal and vaginal flora. The larger sample volume and anaerobic culture would significantly increase the detection rate of microbial contaminated CB. We also found that potential transfusion-transmitted bacterial infection risk still existed in final product although microbial screening was performed.