Transfusion transmitted bacterial infections (TTBI) involving contaminated platelet concentrates: residual risk despite intervention strategies

Background: Transfusion transmitted bacterial infection (TTBI) due to contamination of platelets is an important risk of blood transfusion. Our strategies to decrease bacterial contamination include skin disinfection, diversion of the first blood flow, and bacterial screening. Despite these intervention strategies, a residual risk remains. Methods: To assess this remaining risk, we retrospectively examined TTBI cases registered in the national notification database Transfusion and Transplantation Reactions in Patients (TRIP) during 2008-2019. In addition, we retrospectively examined all cases in which platelets that tested positive in the bacterial screening had already been transfused from 2013 to 2019. The bacterial screening was performed by sampling platelet concentrates 17-25 hours after blood collection, followed by a 7-day incubation of aerobic and anaerobic blood culture bottles in the BacT/ALERT (R) system. The distribution of bacterial species in the bacterial screening of platelets was also characterized. Results: We found 16 cases of possible/probable/certain TTBI associated with platelet transfusion in 2008-2019, including two certain TTBI (with one fatal case); in all of these cases, bacterial screening was negative. From 2013 to 2019, 1,382 out of 432,305 distributed platelets were positive (0.32%) in the bacterial screening, and 469 had already been transfused. In 20 of these 469 cases, a transfusion reaction was reported, 5 potentially related to contaminated buffy coat-derived platelets. Bacterial screening showed mostly skin bacteria, including Cutibacterium spp. and coagulase-negative staphylococci. Most virulent bacteria were detected within 48 hours. Conclusions: In summary, our two approaches demonstrate a small residual risk of TTBI due to platelet contamination, with two certain TTBIs, including one fatal case, per 668,896 distributed platelets during 12 years.