Transfusion-related sepsis after prolonged platelet storage

Platelet transfusion and alternatives to transfusion in patients with malignancy

Platelet transfusions have long had an important role in the treatment of patients with thrombocytopenia due to disease or myelotoxic treatment or in patients with reduced platelet function. However, platelet transfusions are associated with numerous risks, both immunologic (e.g., transfusion reactions, alloimmunization, immunosuppression) and infectious (e.g., viral, bacterial). In addition, several laboratory and clinical factors can influence post-transfusion platelet recovery. Recent technological advances have introduced the potential for using alternatives to platelet transfusions, such as cytokines or platelet substitutes, which may avoid the risks of transfusion. Platelet development from megakaryocytes is a process that is highly regulated by cytokines and animal research suggests that selected cytokines involved in this process may be useful in the treatment of thrombocytopenia. Newer developments, including the utilization of recombinant cytokines with relatively selective stimulation of platelet production (e.g., interleukin 6 [IL-6]) and the recent discovery of a megakaryocyte colony stimulating factor (thrombopoietin), represent major therapeutic opportunities in the treatment of thrombocytopenia. Platelet substitutes, e.g., thromboerythrocytes, also show promise in the management of platelet deficiencies.

Use of leukodepletion filters for the removal of bacteria

Recipient exposure to allogeneic donor leukocytes can mediate a number of immunologic complications of transfusion or can transmit leukotropic viruses carried by the donor. Leukocyte depletion of cellular blood components has been shown to reduce the incidence of such complications. In recent years, prestorage leukocyte depletion by filtration has also been suggested as a means of decreasing the incidence of bacterial overgrowth in cellular blood components. This review analyzes published studies on the use of leukodepletion filters for removal of Staphylococcus epidermidis and Yersinia enterocolitica from blood. Although ineffective for removal of S. epidermidis from Platelet Concentrates, inoculation studies demonstrate removal of low levels of Y. enterocolitica from Red Cell Concentrates. Based on these studies, four possible mechanism(s) for removal of bacteria by leukodepletion filters are analyzed: phagocytosis by leukocytes during a prefiltration holding period; complement-mediated bacterial killing enhanced by filtration; adherence of bacteria to leukocyte surfaces retained within the filter; and direct removal of bacteria by the filter media. Just as multiple mechanisms appear to account for the efficiency with which these filters deplete blood of leukocytes, it is likely that more than one mechanism accounts for the experimental observation that leukocyte depletion filters can reduce overgrowth of Y. enterocolitica in stored Red Cell Concentrates.

Bacterial contamination of blood products and the value of pre-transfusion testing

There has been a dramatic increase recently in the number of reports of septic episodes associated with both red cell and platelet concentrate transfusions. These reports suggest that transfusion-associated septic reactions may occur as often as 1 per 4000 platelet transfusions, however, the true incidence of the bacterial contamination of stored cellular blood components has not yet been established. Recently developed automated techniques for the detection of bacteria are much more rapid than direct plating techniques. Such rapid techniques can be used to monitor the sterility of cellular blood products with greater sensitivity than Gram staining; using a small aliquot of the blood product taken soon after collection. Using such equipment, the incidence of bacterial contamination of 15,838 random donor platelet concentrates collected over a six-month period was determined and evidence of bacterial contamination was found in 32. Seven were classified as confirmed, 10 as unconfirmed and 12 as non-confirmed positives. The confirmed positivity rate was thus 4.4 per 10,000. This rate represents the minimum incidence of bacterial contamination of platelet concentrates and the true rate is likely higher, as some of the unconfirmed positives are likely to have been found to be positives, had the original platelet concentrate been available for culture. The true positive rate is therefore estimated to be between 4.4 and 10.7 per 10,000. Given this rate of bacterial contamination, it is our contention that all platelet concentrate units be monitored for bacteriologic sterility prior to their issue.(ABSTRACT TRUNCATED AT 250 WORDS)

Transfusion-associated bacterial sepsis

The incidence of sepsis caused by transfusion of bacterially contaminated blood components is similar to or less than that of transfusion-transmitted hepatitis C virus infection, yet significantly exceeds those currently estimated for transfusion-associated human immunodeficiency and hepatitis B viruses. Outcomes are serious and may be fatal. In addition, transfusion of sterile allogenic blood can have generalized immunosuppressive effects on recipients, resulting in increased susceptibility to postoperative infection. This review examines the frequency of occurrence of transfusion-associated sepsis, the organisms implicated, and potential sources of bacteria. Approaches to minimize the frequency of sepsis are discussed, including the benefits and disadvantages of altering the storage conditions for blood. In addition, the impact of high levels of bacteria on the gross characteristics of erythrocyte and platelet concentrates is described. The potentials and limitations of current tests for detecting bacteria in blood are also discussed.

Novel automated microbial screening of platelet concentrates

The recovery of bacteria and the speed of detection of microbial growth in platelet concentrates (PC) were studied, comparing a novel automated blood culture system (BacT/Alert) with two traditional methods. Full-scale experiments were performed with a total of 33 units of PC (average content 320 x 10(9) platelets per unit) obtained from pooled buffy coats. Six strains known as possible PC contaminants were tested: S. epidermidis, S. aureus, P. aeruginosa, B. cereus, E. aerogenes, and S. sanguis. Using an inoculum of 50-98 bacteria/ml, bacterial contamination was detected in all of 11 PCs on 132 sampling occasions. With a small inoculum (0.3-9 bacteria/ml), the bacterial contamination was detected in all PCs in which abundant growth appeared, but failed to be detected in some instances where the bacterial content was very small. All of 11 uninoculated PC controls were negative. With the automated method the time for detection of a culture-positive PC was 6-16 h, clearly shorter than with the two manual-visual systems. The new system provides a rapid, reliable, and labour-saving method for screening of bacterial contamination in PCs. This would increase safety particularly if the present 5-day shelf life were extended.

Some storage characteristics of platelet concentrates contaminated with pseudomonas aeruginosa

The present work investigates the effects of contamination with Pseudomonas aeruginosa on some properties of platelet concentrates, i.e. the ability to transmit light, swirling and the degree of platelet activation and cell lysis. 20 pairs of platelet concentrates were studied over a 7 day period. On day 1, one of the concentrates was inoculated with Pseudomonas aeruginosa, while the other served as an identical non-contaminated control. In the contaminated concentrates, swirling and release of platelet factor 4 and lactate dehydrogenase were analysed on day 1, day 2 and day 3; bacterial counts were performed on day 2 and day 3, and on day 7 all these variables were determined in both concentrates. After the 7 day storage period, bacterial growth was found in 13/16 of the contaminated platelet concentrates; all these preparations displayed transmission changes and at least one deviating biochemical parameter. On day 3 all contaminated concentrates had unimpaired swirling, 15/20 had bacterial growth and 10/20 light transmission changes. The study demonstrates that light transmission monitoring on day 3 offers significant advantage (p < 0.05) compared to the visual estimation of swirling. The results also show that the optical method often fails to identify contaminated concentrates during early storage.

Molecular relatedness of Staphylococcus epidermidis isolates obtained during a platelet transfusion-associated episode of sepsis

Staphylococcus epidermidis was isolated from the blood of a 25-year-old pregnant woman following the administration of eight units of platelets. She had developed chills and a fever of 41.4 degrees C soon after the transfusions were completed. S. epidermidis was also obtained from all eight platelet units, as well as from the packed-erythrocyte unit associated with the first unit of platelets. The isolation of the same organism from these epidemiologically related sources provided us with the opportunity to phenotypically and genetically characterize the isolates. Several typing methods, including four molecular techniques, were used to increase our chances of finding any differences between the isolates under investigation. Phenotypic analyses demonstrated that S. epidermidis isolates from the patient, platelet units, and erythrocyte unit reacted in exactly the same manner in 15 biochemical tests, exhibited slime production, and had the same antibiotic susceptibility pattern. Genetic analyses, which included plasmid profiles, plasmid cross-hybridization, field inversion gel electrophoresis, and ribotyping, substantiated the relationships between the S. epidermidis isolates from the patient, platelet units, and erythrocyte unit. Eight S. epidermidis control strains unrelated to the case were found to differ significantly from the platelet-related strain.

A fatal transfusion reaction associated with blood contaminated with Pseudomonas fluorescens

A fatal transfusion reaction due to contamination of platelet-depleted whole blood with Pseudomonas fluorescens is reported. Routine sterility testing on blood products and environmental microbiological monitoring suggested no source for the contaminating organism, as has been the case for the majority of reported incidents of this type. The value of routine sterility testing in the prevention and investigation of such incidents is discussed.

Evaluation of apheresis platelet concentrates stored for 5 days in PL 732 bags

To assess the functional viability of platelets collected by standard apheresis techniques using the Fenwal CS-3000 "closed system" and stored in Fenwal PL 732 plastic bags for 5 days at room temperature with agitation, a number of in vitro parameters (pH, morphology, platelet volume distribution, osmotic recovery, aggregation, and platelet-associated IgG) were examined as a function of storage time. During the first 24 hours of storage, minimal changes were observed in the test parameters with the exception of ADP-induced aggregation (75% decrease [10 uM], 84% decrease [5 microM]). Significant differences were observed between fresh (day 0) and 5-day-old platelet concentrates in all parameters except median platelet volume. These observed changes in in vitro test parameters with storage time are similar to those previously observed for comparably stored random single-donor platelet concentrates. Thus, the "closed-system" PL 732 apheresis platelet concentrates would be expected to be as effective in vivo as random single-donor platelet concentrates, while minimizing recipient exposure to transmissible agents of infectious disease.