Transfusion‐Transmitted Yersinia enterocolitica Infection: Protection Through Buffy Coat Removal and Failure of the Bacteria to Grow in Platelet‐Rich or Platelet‐Poor Plasma

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Abstract
In a previous study, removal of white blood cells (WBC), by filtration 5 h after deliberate contamination of whole blood with a type 0:3 strain of Yersinia enterocolitica, was shown to be an effective way of avoiding bacterial growth in red blood cells (RBC) during storage. In the present study the Opti-System technique was used to remove the buffy coat from whole blood, leaving 10–20% of the original number of WBC in the RBC preparation. In one series of experiments, all of 4 units of RBC suspension, from which buffy coats were removed 2 h after inoculation of 112 colony-forming units (cfu) per ml of Y. enterocolitica, became Yersinia-free, while abundant bacterial growth occurred in all of 4 units where RBC suspension and buffy coat had been recombined. In a second series of 10 experiments, with an inoculum of 80 cfu/ml, no growth was found in platelet-poor plasma stored for 42 days at 4°C. Five out of 10 RBC suspensions in SAGM additive solution remained Yersinia-free throughout a 6-week storage period; 4 of these 10 units showing growth of Yersinia after 4 weeks and 5 after 6 weeks. In the buffy coats bacterial growth was found in 1 out of 10 units after 1 week, 4 after 2 weeks, and in all of 10 units after 4 weeks. In 2 control experiments with WBC-reduced RBC inoculated with the same bacterial dose, growth started within 24 h and was abundant after 1 week. In platelet-rich plasma (PRP), prepared from 4 units of whole blood that had been inoculated with Y. enterocolitica (106 cfu/ml), no bacterial growth was found during 10 days of storage at 22°C. Also, after Y. enterocolitica inoculation (114 cfu/ml) directly into PRP, bacteria failed to grow. We conclude that removal of the buffy coat from whole blood that had been previously contaminated with a moderate inoculation of Y. enterocolitica partly protects the red cells from bacterial growth during storage. The risk of transmitting Y. enterocolitica with platelet-poor plasma, liquid stored at 4°C, seems minimal. This bacterial species shows very poor capacity to grow in PRP at 22°C.