Roslyn Yomtovian

Growth of bacteria in inoculated platelets: implications for bacteria detection and the extension of platelet storage

BACKGROUND: Recent reports from Europe have advocated the use of bacterial culturing of platelets on Day 2 or 3 of storage to extend the shelf life of platelets to 7 days, thereby reducing the outdating of platelets and preserving a limited medical resource. To assess the optimal timing, the necessary sensitivity, and the possible efficacy of bacterial detection, the bacterial growth characteristics were reviewed in 165 platelet units, each inoculated on the day of collection with one of the following organisms: Bacillus cereus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Serratia marcescens, Staphylococcus aureus, and Staphylococcus epidermidis from four previously published studies.

Rituximab for chronic recurring thrombotic thrombocytopenic purpura: a case report and review of the literature

Deficiency of von Willebrand factor (VWF) cleaving protease ADAMTS13 has been demonstrated to be the proximate cause of a subset of thrombotic microangiopathic haemolytic anaemias (MAHA) typical for thrombotic thrombocytopenic purpura (TTP). ADAMTS13 gene mutations cause the hereditary form; acquired deficiency has been attributed to presence of an autoantibody, which may represent a specific subset of MAHA best termed ‘autoimmune thrombotic thrombocytopenic purpura’. We describe a patient with relapsing TTP because of ADAMTS13 inhibitors, who failed to achieve sustained remission despite therapies with plasma exchange, steroids, vincristine, staphylococcal protein A and splenectomy. The ADAMTS13 inhibitor titre remained elevated and clinical stability was only maintained by plasma exchange every 2–3 d over a period of 268 d. The patient then received rituximab therapy (eight doses of 375 mg/m2 weekly), during which she required five plasma exchanges in the first 10 d, two exchanges in the next 3 weeks, and none thereafter for 450 d and ongoing. The ADAMTS13 inhibitor titre decreased and enzyme activity increased. We compared this case with that of seven previously reported TTP cases also treated with rituximab; experience suggests that rituximab therapy deserves further investigation for patients with either refractory or relapsing TTP caused by ADAMTS13 inhibitors.

Evolution of surveillance methods for detection of bacterial contamination of platelets in a university hospital, 1991 through 2004

BACKGROUND:  Platelet (PLT) bacterial contamination (PBC) is the most common transfusion‐associated infection. It is important to understand the impact of interventions addressing this problem.

Don't bug me: the problem of bacterial contamination of blood components--challenges and solutions.

Volume 41, November 2001 TRANSFUSION 1331 www.transfusion.org Transfusion of bacterially contaminated blood components, especially platelets, is an ongoing problem with variable clinical sequelae, including serious morbidity and mortality.1 Over the last three decades, attention has been focused on the risk of virus transmission by the transfusion of blood components. Considerable progress has been made in this area, and the transmission of viruses such as HIV, HTLV, HBV, and HCV has been greatly reduced.2 Transmission of these viruses is currently estimated to be between 1 and 4 per million blood components transfused, or 25 to 100 cases per year in the United States, and this is likely to be further reduced by the introduction of NAT for these viruses.3 In contrast, bacterial contamination of blood components is currently the most frequent infectious complication of blood component use, with an estimated incidence of 1 in 2,000 to 3,000 platelet units and 1 in 30,000 RBC units.4-7 Bacterial contamination therefore exceeds by far that of viral agents, and we now need to devote our resources to tackling this problem. The prevalence of severe episodes of transfusion-associated bacterial sepsis has not been clearly established, but is estimated to occur in connection with about one-sixth of contaminated units transfused.2,6,7 With 9 million platelet units and 12 million RBC units transfused in the United States per year,8 3000 to 4500 and 24 cases of sepsis, respectively, per year are likely to occur because of bacterially contaminated components, with 500 to 750 cases being severe and possibly fatal. The gaps in our knowledge of the actual incidence of blood component contamination and the clinical consequences thereof are due to variability in case definition, in the bacterial species involved, in the protocols for detecting and confirming bacterial contamination, and in the age of transfused platelet units, with 4and 5-day-old units exhibiting the greatest risk.6,9,10 Recognition of bacterial contamination of blood components typically occurs only in a small subset of patients with severe, immediate, septic transfusion reactions. A recent national study, the Bacterial Contamination of Blood and Blood Products (BaCon) Study,11 was designed to detect severe, immediate transfusion reactions. This study detected 38 clinically proven cases of severe reactions to the transfusion of bacterially contaminated blood components, predominantly platelets, over a 2-year period; the mortality rate among these cases was 42 percent (16/38). Bacteria isolated included 12 Enterobacteriaceae, 2 Pseudomonas aeruginosa, 5 Staphylococcus aureus, 10 coagulase-negative staphylococci, 4 streptococci, 1 Bacillus species, and 4 mixed flora or other organisms. While the annual incidence of severe, immediate transfusion reactions in the United States, as extrapolated from the BaCon Study (27 cases/year), is far lower than the number expected from estimates discussed earlier (500-750 cases/ year), the BaCon Study shows that bacterial contamination is a real problem and that it has resulted in 16 well-documented deaths. These cases represent only the “tip of the iceberg,” and the real incidence is undoubtedly considerably greater. Therefore, as in most cases, the bacterial contamination of transfused blood components is unrecognized and undetected, and an active surveillance program is needed to establish the true extent of the problem. Detection is best achieved by culturing all components at the time of use. As platelet components have the highest incidence of contamination because of their storage at 22°C, we have studied platelet contamination in our institution over the last 10 years, employing prospective microbiologic surveillance of single-donor apheresis and pooled random-donor platelet (RDP) units before transfusion or at the end of the storage time if unused.12 The surveillance methods used included Gram’s staining and culture of 1to 2-mL samples of apheresis units or pooled RDP units at the time of issue. All cultures were performed quantitatively, and results were confirmed as true-positive only if the same result was detected on repeat culture of the platelet sample held at 4°C and, in the case of RDP pools, if the same organism was recovered from one of the units that made up the pool. This has revealed that the incidence of bacterial contamination is about 1 in 2000 RDP units (or 1/400 RDP pools of 5 units) and 1 in 2400 apheresis units.5,12 The incidence of contamination of platelet units was not significantly different for RDP and single-donor apheresis units, but the transfusion risk is much higher with RDP units, being the multiple of the number of units per pool. Significant bacterial contamination (defined as bacterial contamination of a platelet unit or pool whose transfusion results in a septic reaction, or a bacterial inoculum in a platelet unit or pool that is high enough to be detected by a pretransfusion Gram’s stain) occurred in approximately 1 in 400 pooled platelet transfusions containing at least one 4or 5-day-old unit.5 In particular, we demonstrated that the incidence of significant bacterial contamination of platelets was considerably greater Don’t bug me: the problem of bacterial contamination of blood components—challenges and solutions E D I T O R I A L

Lowering the Prophylactic Platelet Transfusion Threshold: a Prospective Analysis

The 20 × 109/L threshold for prophylactic platelet transfusion may be unnecessarily high. Few prospective studies, however, in which other trigger values were tested have been published. In this study all hospitalized, thrombocytopenic adult hematology-oncology patients in our institution were prospectively evaluated daily for hemorrhage and platelet transfusion during a one year period; no patients were excluded for bleeding or infectious problems. By design, during the initial six-months (baseline period), the prophylactic platelet transfusion trigger was 20 × 109/L; for the second six-months (study period) this threshold was changed to 10 × 109/L. Patients studied during the two periods did not differ significantly in age, gender, diagnosis, blood or marrow transplant status, and duration of neutropenia. Compliance with the thresholds was 95.6% (baseline period) and 93.5% (study period). For patients with platelet counts under 20 × 109/L, the mean use of platelet transfusions per patient per day was significantly lower in the study period (4.47) than in the baseline period (6.48; p < 0.001). Both mean prophylactic (1.54/patient-day) and therapeutic (2.93/patient-day) platelet transfusions were reduced in the study period compared with the baseline period (2.26 and 4.22/patient-day, respectively). Hemorrhage was slightly reduced in the study period compared with the baseline period: major hemorrhage, 15.2% vs. 18.4% (p = 0.014); minor hemorrhage, 63.6% vs. 70.1% (p < 0.001). Thus, hemorrhage was not increased with the lower trigger level. A 10 × 109/L prophylactic platelet transfusion threshold value is safe and effective.

Prevalence of Platelet Transfusion Reactions Before and After Implementation of Leukocyte‐Depleted Platelet Concentrates by Filtration

To determine the impact of platelet leukodepletion by filtration on the overall prevalence of reported transfusion reactions associated with platelet concentrates, we audited platelet transfusion reactions after infusion of platelet concentrates reported at University Hospitals of Cleveland over 6 months before (interval 1, July 1, 1989 to December 31, 1989) and after (interval 2, July 1, 1990 to December 31, 1990) implementation of the Pall PL 50 filter on our adult Hematology‐Oncology inpatient unit (Division 60). Thirty‐two (1.7%) of 1,901 random, pooled platelet transfusion events resulted in blood bank transfusion reaction workups in interval 1, compared to 90 (5.3%) of 1,704 in interval 2 (p<0.001). The Division 60 service accounted for more of our hospital‐wide platelet reactions after implementation of the filter in interval 2 (84%) than before filtration in interval 1 (42%), p = 0.002. The prevalence of reaction workups for Division 60 was 0.6% for interval 1, compared to 4.3% for interval 2 (p<0.001). No differences were found between interval 1 and interval 2 for the rate of discontinuation of platelet transfusion (36 vs. 32%, p = 0.14), rate of premedication for platelet transfusion (72 vs. 65%, p = 0.6), percentage of direct antiglobulin test‐positive reactions (17 vs. 5.4%, p = 0.09), percentage showing icteric/hemolyzed serum (15 vs. 4.4%, p = 0.09), or reactions believed to be due to red blood cell incompatibility (8.8 vs. 1.1%, p = 0.1). We conclude that the use of expensive platelet filtration devices has not decreased the morbidity of random, pooled platelet transfusions, nor the prevalence of time‐consuming blood bank evaluation of platelet transfusion reactions in this setting.

Bacterial contamination of blood: lessons from the past and road map for the future.

Progress, far from consisting in change, depends on retentiveness. Those who cannot remember the past are condemned to repeat it.

Detection of bacterial contamination of platelet concentrates.

R. N. I. Pietersz, C. P. Engelfriet, H. W. Reesink, E. M. Wood, S. Winzar, A. J. Keller, J. T. Wilson, G. Henn, W. R. Mayr, S. Ramírez-Arcos, M. Goldman, J. Georgsen, P. Morel, P. Herve, G. Andeu, A. Assal, E. Seifried, M. Schmidt, M. Foley, C. Doherty, P. Coakley, A. Salami, E. Cadden, W. G. Murphy, M. Satake, D. de Korte, V. Bosnes, J. Kjeldsen-Kragh, C. McDonald, M. E. Brecher, R. Yomtovian & J. P. AuBuchon

Enhancement of a culture-based bacterial detection system (eBDS) for platelet products based on measurement of oxygen consumption

BACKGROUND: An enhanced bacterial detection system (Pall eBDS) was developed that distinguishes itself from its predecessor (Pall BDS) by removal of the platelet (PLT)‐retaining filter allowing for optimal bacterial transfer, modification of the culture tablet to reduce the confounding effects of respiring PLTs while enhancing bacterial growth, and facilitation of nutrients and gas exchange by agitating the sample pouch during incubation at 35°C. The objective was to evaluate the performance of the new eBDS.

Evaluation of the Scansystem method for detection of bacterially contaminated platelets

BACKGROUND:  Platelet (PLT) bacterial contamination occurs in approximately 1 in 2000 PLT units. The College of American Pathologists recommends and AABB requires procedures to detect PLT bacterial contamination. Although two methods, BacT/ALERT (bioMérieux) and Pall BDS (Pall Corporation), have FDA approval for quality control testing, additional methods are in development. One such method was evaluated, the Scansystem (Hemosystem), which has been developed for use on leukoreduced PLT components between 30 and 72 hours after collection.