Screening of platelet concentrates for bacterial contamination: spectrum of bacteria detected, proportion of transfused units, and clinical follow-up.

Screening of platelet concentrates (PCs) for bacterial contamination with cultivation methods is carried out as a routine procedure in some countries. The aim is to prevent the transfusion of contaminated PCs. The German Evaluation of Regular Monitoring Study Group conducted a prospective multicenter study on 52,243 PCs to investigate the prevalence of bacteria (BacT/ALERT, bioMerieux). This study describes the detected bacterial spectrum, the proportion of PCs with a positive test result that had been transfused, and the results of the clinical follow-up. One hundred thirteen (67%) of 169 potentially or confirmed positive units had already been transfused at the time of the first positive signal. The transfusion of units contaminated by Staphylococcus aureus, Serratia marcescens, and 73% of the units contaminated with Staphylococcus epidermidis, Staphylococcus capitis, or Staphylococcus saccharolyticus was prevented. In contrast, 85% of units with Propionibacterium acnes were transfused. A clonal relationship of the isolates from the pooled PCs and from the associated red blood cell concentrates was found in all investigated cases. The follow-up revealed six febrile reactions to culture-positive PCs not classified as transfusion reaction (TRs) by treating physicians. This demonstrates the importance of hemovigilance. Serious septic reactions due to Klebsiella pneumoniae in two units of one apheresis PC that had tested false-negative were reported; one had a fatal outcome. Culture systems reduce the risk of transfusion of contaminated PCs but cannot guarantee sterility. Physicians must be aware of bacterial contamination of PCs as a potential cause of TRs and must report all adverse events.

Bacterial contamination of platelet concentrates: results of a prospective multicenter study comparing pooled whole blood-derived platelets and apheresis platelets.

BACKGROUND: The GERMS Group initiated a prospective multicenter study to assess prevalence and nature of bacterial contamination of pooled buffy-coat platelet concentrates (PPCs) and apheresis platelet concentrates (APCs) by routine screening with a bacterial culture system. STUDY DESIGN AND METHODS: In nine centers overall, 52,243 platelet (PLT) concentrates (15,198 APCs, 37,045 PPCs) were analyzed by aerobic and anaerobic cultures (BacT/ALERT, bioMérieux). RESULTS: In 135 PLT concentrates (PCs; 0.26%), bacteria could be identified in the first culture (0.4% for APCs vs. 0.2% for PPCs; p < 0.001). In 37 (0.07%) of these PC units, the same bacteria strain could be identified in a second culture from the sample bag and/or the PC unit. The rate of confirmed-positive units did not differ significantly between APC (0.09%; 1/1169) and PPC units (0.06%; 1/1544). Bacteria from skin flora (Propionibacterium acnes, Staphylococcus epidermidis) were the most prevalent contaminants. Median times to first positive culture from start of incubation were 0.7 and 3.7 days in aerobic and anaerobic cultures for confirmed-positive units. With a "negative-to-date" issue strategy, most PC units (55%) had already been issued by time of the first positive culture. CONCLUSION: The rate of confirmed bacterial contamination of PC units was low. Nevertheless, clinicians must be aware of this risk. The risk of bacterial contamination does not warrant universal preference of APCs. It must be questioned whether routine bacterial screening by a culture method can sufficiently prevent contaminated products from being transfused due to the delay until a positive signal in the culture system and due to false-negative results.