BACTERIAL CONTAMINATION OF CELLULAR BLOOD COMPONENTS

The catastrophic effect of the infusion of a blood product containing bacteria has been recognized for many years as a serious complication of blood transfusion. [l-61 With the advent of closed plastic systems for the collection, preparation, and storage of blood products, it appeared that the aseptic preparation of whole blood into its various components was a reality. Those involved in transfusion medicine believed they no longer had to worry about septic reactions associated with the use of blood products and the occasional report of a septic transfusion reaction was deemed an unavoidable occurrence. Thus, the advent of the closed blood collection system lulled those involved in the provision of blood products into a false sense of security about the aseptic nature of the blood supply. The AIDS epidemic and the realization, during the past decade, that AIDS could be transmitted by blood product transfusions forced those involved in their provision to pay considerably more attention to the quality of the blood products they provided for patient care. In particular, since the start of the AIDS era there has been increased attention paid to the transmission of infectious agents to recipients of blood products. The main focus of this attention, though, was on the transmission of viruses. Until recently, little attention has been paid to the possibility of transfusion-associated bacterial septic reactions, as these were being recognized only infrequently. [7] Recently, there has been a dramatic increase in the number of reports of transfusion-associated septic episodes. [8-12] In addition, septic episodes due to unusual organisms such as Yersinia enterocolitica have been reported. The latter is an enteric organism capable of efficient proliferation and even selective growth at refrigeration temperatures (4"C). [13-16] Interestingly, most septic episodes due to Yersinia enterocolitica appear to have occurred after red cell concentrate storage at 4°C for 21 days. It was thus suggested that the storage period of red cell concentrates be reduced from 6 weeks to 3 weeks to prevent such episodes. Such an approach was not adopted because of concern that a reduction in storage time would exacerbate possible red cell shortages. [l7,18] It is important to point out that transfusion associated sepsis is not a problem only for allogeneic blood product recipients but also for recipients of syngeneic (autologous) blood products. A case of septic shock due to Yersinia enterocolitica was reported recently during a syngeneic red cell transfusion administered during surgery. [l9] Thus while syngeneic blood donor programs prevent immunological consequences in recipients, they do not ensure microbiological safety. Septic episodes associated with platelet transfusions, with few exceptions, have gone unrecognized because of the frequent occurrence of reactions in patients receiving platelet concentrates. [5,6,8,20,21] Up to 30% of patients receiving platelet concentrates experience an adverse reaction during or immediately following an infusion. Most of these are not due to the presence of bacteria and have usually been attributed to recipient alloantibodies to antigens on donor leukocytes. [8] Interestingly, there has been recent evidence indicating that such reactions may be associated with the release of cytokines by contaminating leukocytes present in varying numbers in random donor platelet concentrates. These cytokines probably cause many of the signs and symptoms associated with febrile non-hemolytic transfusion reactions (FNHTR) associated with platelet concentrate use. [22] Because the signs and symptoms associated with FNHTR are similar to those seen in patients with septic reactions due to the presence of bacterial contaminants in transfused platelets, the latter may have often gone unrecognized as due to bacteria.