Blood surveillance and detection on platelet bacterial contamination associated with septic events

The objective of this study was to evaluate the risk of transfusion-associated septic events in Taiwan. In Taiwan, most blood components are provided from blood centres; so platelet (PLT) bacterial contaminations are rarely reported. The study's aim is to investigate the prevalence of PLT bacterial contamination in Kaoshiung Armed Forces General Hospital by using BacT/ALERT system for routine screening.
A total of 82 apheresis and 2256 whole blood-derived PLT units were tested. A measured quantity of 1 mL aliquots were taken as samplings from all blood bag tubing of PLT units, and then further incubated in a bacterial detection system (BacT/ALERT). The subcultures of true-positive bottles underwent bacterial identification by using Vitek system, microscopic observation and culture-based methods. Eight units (0·34%, 8 of 2338) were found to have bacterial contamination. The true-positive rate of the whole blood-derived and apheresis PLTs was 0·31% (7 of 2256) and 1·22% (1 of 82), respectively. Six microorganisms were identified with the most dominate being Staphylococcus epidermidis . One case of transfusion-associated sepsis was confirmed; in addition, the holding period of PLTs ( F = 4·522, P = 0·034) and positive detection of PLT bacterial contamination ( F = 46·605 ,P < 0·001) were associated with post-transfusion sepsis. Thus, in this study, although the transfusion-associated septic event was rarely found and PLT units were provided from blood centres, bacterial screening was necessary to safely quarantine the transfusion. The holding period of PLT units should be no more than 4 days in order to avoid possible bacterial contamination.     

Improving the bacteriological safety of platelet transfusions

Despite the increased application of aseptic techniques for blood collection and the preparation of platelet concentrates, morbidity and mortality arising from the transfusion of bacterially contaminated allogeneic platelet products persist. This problem exists because stored platelet concentrates represent a nearly ideal growth medium for bacteria and because they are stored at temperatures (22 degrees +/- 2 degrees C) that facilitate bacterial growth. The presence of bacteria in blood components including platelets has been a problem for many decades and currently is the most common microbiological cause of transfusion-associated morbidity and mortality. A variety of strategies have been devised and/or proposed in an attempt to try to reduce the risk of transfusion-associated sepsis. These include pretransfusion bacterial detection, efforts to reduce the likelihood of bacterial contamination, the optimization of blood product processing and storage, reducing recipient exposure, and the introduction of pathogen inactivation methodology. With regard to doing bacterial detection, a number of automated detection systems have become available to test for contaminated platelet components, but their utility to some extent is restricted by the time they take to indicate the presence of bacteria and/or their lack of sensitivity to detect initially low bacterial loads. A variety of other approaches has been shown to reduce the risk of bacterial contamination and include filtration to remove leukocytes and bacteria, diversion of the initial aliquot of blood during donation, and improved donor skin disinfection. Platelet pathogen inactivation methods under investigation include the addition of L-carnitine, gamma-irradiation, riboflavin plus UVA irradiation, and amotosalen HCl plus UVA irradiation. The latter process is licensed for clinical use with platelets in some countries in Europe. All of these approaches, either collectively or individually, hold considerable promise that the prevalence of adverse events associated with bacteria in platelet products will decline significantly in the very foreseeable future.     

Risks of blood transfusion and their prevention

As a result of significant progress in reducing the risks of transfusion-transmitted viral infections, bacterial contamination of platelet components (1:2,000) and sepsis (1:50,000) are now the most frequent infectious complications of blood transfusions. Sepsis from bacterial contamination of red cell components is less frequent (1:500,000), because red blood cells, unlike platelet components, can be stored at refrigerated temperatures (1 degrees C-4 degrees C). Current risks for transfusion-transmitted viral diseases (per blood component transfused) are: human immunodeficiency virus, 1:2,135,000; hepatitis C virus, 1:1,935,000; hepatitis B virus, 1:205,000; and human T-lymphotropic viruses, 1:2,993,000. Transfusion-transmitted babesiosis has increased morbidity and mortality for splenectomized patients. Immunocompromised recipients are at increased risk of developing Chagas disease from blood contaminated by Trypanosoma cruzi. Reports of transfusion-related acute lunge injury and transfusion-associated graft-versus-host disease increase each year as physicians become increasingly aware of their varied clinical presentations. While strategies for preventing infections complications focus primarily on blood donor services, individual physicians can reduce risks to their patients by maintaining conservative "triggers" for transfusions, prescribing pharmacologic agents to reduce bleeding (antifibrinolytic drugs, serine protease inhibitors, fibrin sealants), and using epoetin alpha to reduce transfusion of red cells in selected patients.     

Transfusion of blood products and nosocomial infection in surgical patients

PURPOSE OF REVIEW: Liberal transfusion of blood products may be associated with a worse clinical outcome, including in-hospital mortality. This review focuses on the mechanisms by which transfusions may result in an increased risk of bacterial infection. RECENT FINDINGS: The association between blood transfusion and worse outcome has been attributed to suppression of the recipient's immune function, the so called transfusion-related immunomodulation effect, as well as changes that may occur as blood ages. Despite several attempts to identify the mechanism by which transfusion worsens outcomes, this mechanism, as well as the role of leukoreduction in the mitigation of transfusion-related immunomodulation, have yet to be demonstrated. Bacterial contamination of the blood supply has become a serious problem in the past 20 years, and is currently the second leading cause of transfusion-associated death. Since the implementation of specific platelet transfusion protocols, the incidence of morbidity and mortality caused by infected platelet units appears to be markedly reduced. SUMMARY: Transfusion of blood and blood products can be life-saving interventions. Consequences of transfusion may ultimately result in worse outcomes. More research will be required in order to identify indications and practices that optimize outcomes of surgical patients who require a blood transfusion.     

Incidence of bacterial transmission and transfusion reactions by blood components.

Successful reduction of the risk of viral transmission via blood components has focused attention on the risk of transfusion-associated bacterial sepsis. The incidence of transfusion reactions due to bacteria is currently estimated at between 1 per 100,000 and 1 per 1,000,000 units in the case of packed red blood cells and between 1 per 900 and 1 per 100,000 units in the case of platelet concentrates. For autologous transfusion, only isolated case reports are available which do not permit a quantitative risk assessment. No reliable data on the risk of morbidity and mortality due to transfusion-associated bacterial infection are available for Germany at present. As platelet concentrates provide more favourable conditions for bacterial growth by virtue of being stored at room temperature, these blood components are thought to bear a considerably greater risk of bacterial contamination than red blood cells. The rate of contamination of platelet concentrates is cited at between 0.02% and 1.2%, depending on the production and bacterial culture techniques used, whereas the rate for packed red blood cells is between 0.1% and 0.2%. Risk reduction strategies include careful selection of blood donors, optimisation of donation and production techniques, and detection of bacteria in samples of blood components prior to transfusion. Also of importance for patient safety are quality assurance measures in the preparation for transfusion, in measures of patient monitoring, and investigation of transfusion reactions.     

Detecting bacterial contamination in platelet products

Bacterial contamination of platelets is an important cause of transfusion-associated morbidity and mortality. It is currently the most frequent infectious complication of transfusion therapy, with between 1 in 1,000 and 1 in 3,000 platelet units being bacterially contaminated at time of transfusion. Several factors have contributed to the persistence of this problem including lack of sensitive detection methods, lack of recognition of the frequency of the problem, inadequate recognition of septic reactions by clinicians treating patients receiving platelet transfusions, differences in transfusion reactions between bacterial species and bacterial inocula transfused, and differing methodologies and time of testing for detection of bacteria in platelet units. There are also important correlations between the receipt of bacterially contaminated platelet units and the development of transfusion reactions and bacteremia. In the last few years the recognition of the importance of platelet bacterial contamination prompted the College of American Pathologists (CAP) and the American Association of Blood Banks (AABB) to set new standards requiring the screening of platelets for bacterial contamination. In the wake of these standards, an increasing number of approaches have been and are being developed to deal with this problem. The clinical sensitivity, specificity and predictive value of these detection methods vary considerably and need to be defined for routine laboratory practice. In this review, we focus on the practical aspects and feasibility of implementing FDA-cleared detection methods for identifying bacterially contaminated platelet units. We also present details of a number of methods under development for at-issue use.     

Cost-effectiveness of pathogen inactivation for platelet transfusions in the Netherlands

The objective of this study is to estimate cost-effectiveness of pathogen inactivation for platelet transfusions in the Netherlands. We used decision tree analysis to evaluate the cost-effectiveness of the addition of pathogen inactivation of pooled platelets to standard procedures for platelet transfusion safety (such as, donor recruitment and screening). Data on transfusions were derived from the University Medical Centre Groningen (the Netherlands) for 1997. Characteristics of platelet recipients (patient group, age, gender and survival) and data/assumptions on viral and bacterial risks were linked to direct and indirect costs/benefits of pathogen inactivation. Post-transfusion survival was simulated with a Markov model. Standard methods for cost-effectiveness were used. Cost-effectiveness was expressed in net costs per life-year gained (LYG) and estimated in baseline- and sensitivity analysis. Sensitivity was analysed with respect to various assumptions including sepsis risk, reduction of the discard rate and discounting. Stochastic analysis to derive 90% simulation intervals (SIs) was performed on sepsis risk. Net costs per LYG for pathogen inactivation were estimated 554,000 euro in the baseline-weighted average over the three patient groups (90% SI: 354,000-1092,500 euro). Sensitivity analysis revealed that cost-effectiveness was insensitive to viral risks and indirect costing, but highly sensitive to the assumed excess transfusions required and discounting of LYG. Given relatively high net costs per LYG that are internationally accepted for blood transfusion safety interventions, our estimated cost-effectiveness figures for pathogen inactivation may reflect acceptable cost-effectiveness in this specific area. Two main assumptions of our model were that the pathogen inactivation was 100% effective in preventing transmission of the pathogens considered and was not associated with major and/or costly adverse reactions. Validation of several crucial parameters is required, in particular the Dutch risk for acquiring and dying of transfusion-related sepsis.     

Strategies for the avoidance of bacterial contamination of blood components

Gram staining and bacterial culturing methods were used to determine the incidence of bacterial contamination of cellular blood components at the time of transfusion reactions. Over a 5-year period, 2208 (4.3%) of 51,278 transfusions were complicated by reactions. Overall bacterial contamination occurred in 5 (0.03%) of 17,928 transfusions of single- donor apheresis platelets, 1 (0.14%) of 712 transfusions of pooled random-donor platelet concentrates, 1 (0.003%) of 31,385 transfusions of red cells, and 0 of 1253 transfusions of fresh-frozen plasma. Gram staining done at the time of positive cultures was positive in three of six cases. Although six of seven recipients of contaminated components suffered no clinical sequelae, contaminated transfusions may have been a contributing cause of death in one case. Attempts were made to avoid the transfusion of contaminated cellular blood components by performing routine bacterial cultures: 0 of 341 quality control cultures were positive. To avoid the transfusion of contaminated platelets by identifying bacteria, Gram staining was performed in all single-donor apheresis platelet units collected on open systems and daily in platelets stored > 48 hours: 8 (0.15%) of 5334 smears done on 3829 platelet units were interpreted as positive, and those units were not transfused, but only two of eight units were culture positive. These studies suggest that bacterial contamination can result in adverse clinical sequelae in transfusion recipients and that both culturing and Gram staining are poor methods of screening for contaminated units. More sensitive and specific methods of generalized screening for bacterial contamination are needed.     

Implementation of Bacterial Detection Methods into Blood Donor Screening - Overview of Different Technologies

SUMMARY: BACKGROUND: Through the implementation of modern technology, such as nucleic acid testing, over the last two decades, blood safety has improved considerably in that the risk of viral infection is less than 1 in a million blood transfusions. By contrast, the residual risk of transfusion-associated bacterial infection is stable at approximately 1 in 2,000 to 1 in 3,000 in platelets. To improve blood safety with regard to bacterial infections, many countries have implemented bacterial screening methods as part of their blood donor screening programmes. METHODS: BACTERIAL DETECTION METHODS ARE CLUSTERED INTO THREE GROUPS: i) culture methods in combination with the 'negative-to-date' concept, ii) rapid detection systems with a late sample collection, and iii) bedside screening tests. RESULTS: The culture methods are convincing because of their very high analytical sensitivity. Nevertheless, false-negative culture results and subsequent fatalities were reported in several countries. Rapid bacterial systems are characterised as having short testing time but reduced sensitivity. Sample errors are prevented by late sample collection. Finally, bedside tests reduce the risk for sample errors to a minimum, but testing outside of blood donation services may have risks for general testing failures. CONCLUSION: Bacterial screening of blood products, especially platelets, can be performed using a broad range of technologies. Each system exhibits advantages and disadvantages and offers only a temporary solution until a general pathogen inactivation technology is available for all blood components.     

‘Sterility Testing of Blood Components and Advanced Therapy Medicinal Products’ (Munich,April 29, 2010) Organized by the DGTI Section ‘Safety in Hemotherapy’ - Meeting Report

Neither screening method completely detects all clinically relevant bacterial contaminations. The effect of sampling time and volume as well as standardization of the assay applied has also to be taken into account. Therefore, minimizing the risk of contamination during manufacture by measures such as donor selection, skin disinfection, division, and processing within closed systems remains crucial. In this context new concepts in sterility testing, especially with instable advanced therapy medicinal products (ATMPs), are needed as well as reassessment of pathogen inactivation techniques. At present hemovigilance data indicate that shortening the shelf life of platelet concentrates as introduced in Germany 2008 reduced the risk of transfusion-transmitted bacterial infections to the same extent as bacterial screening as done in Canada or the Netherlands. The evolving methodological progress, e.g. by standardizing culture methods or enhancing detection systems, requires careful follow-up in parallel to hemovigilance data in order to ensure optimal bacterial safety in hemotherapy.     

10 Years Experience with Bacterial Screening of Platelet Concentrates in the Netherlands

SUMMARY: BACKGROUND: Contamination of platelets with bacteria is the major microbiological risk of blood transfusion. Screening for bacterial contamination can reduce the frequency of bacterial transmission considerably. In the present paper, the results of 10-year screening in the Netherlands are described. METHODS: All platelet concentrates were cultured with the BacT/Alert culturing system with large volume (7.5 ml) cultures in either an aerobic or an anaerobic bottle. Products were released on a 'negative-to-date' basis. RESULTS: After introduction of the diversion of the first milliliters of collected blood, the number of positive screening cultures decreased significantly from 0.85% to 0.37%. The frequency of transfusion-transmitted bacterial infections by platelet concentrates is currently less than 1 per 2 years in the Netherlands. CONCLUSION: Over a period of 10 years the bacterial screening system for platelet concentrates proved to result in a safe system with respect to microbiological infection as a result of platelet transfusions.     

Applications of real-time PCR in the screening of platelet concentrates for bacterial contamination

Although there have been major improvements over the past few decades in detection methods for blood-borne infectious agents, platelet concentrates are still responsible for most cases of transfusion-transmitted bacterial infections. To date, real-time PCR is an indispensable tool in diagnostic laboratories to detect pathogens in a variety of biological samples. In this article, the applications of this powerful technique in the screening of platelet concentrates for bacterial contamination are discussed. Next to pathogen-specific (real-time) PCR assays, particular attention is directed to the recently developed 16S rDNA real-time PCR. This assay has been proven as a convenient way to detect bacterial contamination of platelet concentrates. The assay is sensitive and enables rapid detection of low initial numbers of bacteria in platelet concentrates. The short turnaround time of this assay allows high-throughput screening and reduction of the risk of transfusion of bacterially contaminated units. As with every method, real-time PCR has its advantages and disadvantages. These and especially limitations inherent to generation of false-positive or -negative results are emphasized. The universal nature of detection of the assay may be suitable for generalized bacterial screening of other blood components, such as red blood cells and plasma. Therefore, it is necessary to adapt and optimize detection in red blood cells and plasma with real-time PCR. Further sophistication, miniaturization and standardization of extraction and amplification methods should improve the total performance and robustness of the assay. Hence, real-time PCR is an attractive method in development as a more rapid screening test than currently used culture methods to detect bacterial contamination in blood components.     

Current and future trends in transfusion therapy

The increase in intensive treatment for cancer has impacted blood product transfusion practices. Transfusion guidelines are primarily institution specific, but the general concepts and theories are universal. Blood product screening has decreased the risk of transfusion-acquired infections; however, the risk is not obsolete. This article reviews current approaches to platelet, white blood cell, and red blood cell transfusions, as well as risks associated with these therapies (e.g., infection and transfusion-associated graft-versus-host disease). Pertinent laboratory studies, patient assessment, blood product administration, and patient education is discussed. The current approaches to platelet, white blood cell, and red blood cell transfusions are constantly changed and evaluated. Pediatric oncology nurses must stay up to date with these changes to provide optimal patient care.     

Bacterial infections associated with blood transfusion: experience and perspective of infectious diseases consultants

BACKGROUND: On March 1, 2004, the AABB adopted a new standard that requires member blood banks and transfusion services to implement measures to limit and detect bacterial contamination in all platelet (PLT) components. The AABB has since developed several guidelines to assist blood transfusion services and blood banks in this area, some of which are relevant to clinical practice. Knowledge and experience among clinicians (including infectious disease consultants, who can play an important role in managing patients with sepsis) concerning risk of bacterial infections associated with transfusion, however, are unknown. STUDY DESIGN AND METHODS: Experience concerning management and prevention of transfusion-associated bacterial infection, including knowledge of the AABB standard requiring bacterial screening of PLTs, was assessed through an Infectious Diseases Society of America Emerging Infections Network (IDSA/EIN) survey. RESULTS: Overall, 405 (47%) EIN members responded to the survey; of those responding, 12 percent of respondents had encountered transfusion reactions potentially due to bacterial contamination in the prior 10 years, 36 percent were aware of the transmission risk of bacteria through blood transfusion, and 20 percent were aware of the new AABB standard for bacterial screening of PLTs. CONCLUSIONS: Understanding by EIN infectious disease consultants of the significance of transfusion-associated bacterial infection and associated AABB standards and guidelines may indicate lack of other clinicians' awareness on these issues. Improving awareness of the risk of bacterial contamination of PLTs appears warranted to improve clinical management of infected blood donors or recipients, particularly when follow-up for transfusion of a culture-positive PLT unit is needed.     

Transfusion-Transmitted Infections Reported to the National Healthcare Safety Network Hemovigilance Module

Transfusion-transmitted infections (TTIs) can be severe and result in death. Transfusion-transmitted viral pathogen transmission has been substantially reduced, whereas sepsis due to bacterial contamination of platelets and transfusion-transmitted babesiosis may occur more frequently. Quantifying the burden of TTI is important to develop targeted interventions. From January 1, 2010, to December 31, 2016, health care facilities participating in the National Healthcare Safety Network Hemovigilance Module monitored transfusion recipients for evidence of TTI and recorded the total number of units transfused. Facilities use standard criteria to report TTIs. Incidence rates of TTIs, including for bacterial contamination of platelets and transfusion-transmitted babesiosis, are presented. One hundred ninety-five facilities reported 111 TTIs and 7.9 million transfused components to the National Healthcare Safety Network Hemovigilance Module. Of these 111 reports, 54 met inclusion criteria. The most frequently reported pathogens were Babesia spp in RBCs (16/23, 70%) and Staphylococcus aureus in platelets (12/30, 40%). There were 1.95 (26 apheresis, 4 whole blood derived) TTIs per 100 000 transfused platelet units and 0.53 TTI per 100 000 transfused RBC components, compared to 0.68 TTI per 100 000 all transfused components. Bacterial contamination of platelets and transfusion-transmitted babesiosis were the most frequently reported TTIs. Interventions that reduce the burden of bacterial contamination of platelets, particularly collected by apheresis, and Babesia transmission through RBC transfusion would reduce transfusion recipient morbidity and mortality. These analyses demonstrate the value and importance of facility participation in national recipient hemovigilance using standard reporting criteria.     

Bacterial contamination of blood components: Norwegian strategies in identifying donors with higher risk of inducing septic transfusion reactions in recipients

Bacterial contamination of blood and its cellular components remains the most common microbiological cause of transfusion associated morbidity and mortality, even in developed countries. This yet unresolved complication is seen more often in platelet transfusions, as platelet concentrates are stored at room temperature, in gas permeable containers with constant agitation, which support bacterial proliferation from relatively low undetectable levels, at the beginning of storage time, to relatively high virulent bacteria titers and endotoxin generation, at the end of shelf life. Accordingly, several combined strategies are introduced and implemented to at least reduce the potential risk of bacterial contaminated products for transfusion. These embody: improved donors arms cleaning; bacterial avoidance by diversion of the first portion of collection; reducing bacterial growth through development of newer storage media for longer platelet shelf life; bacterial load reduction by leucoreduction/viral inactivation, in some countries and eliminating the use potentially contaminated units through screening, through current available testing procedures, though none are not yet fully secure. We have not seen the same reduction in bacterial associated transfusion infections as we have observed for the sharp drop in transfusion associated transmission rates of HIV and hepatitis B and C. This great viral reduction is not only caused by the introduction of newer and more sensitive and specific detection methods for different viruses, but also the identification of donor risk groups through questionnaires and personal interviews. While search for more efficient methods for identifying potential blood donors with asymptomatic bacteremia, as well as a better way for detecting bacteria in stored blood components will be continuing, it is necessary to establish more standardized guidelines for the recognition the adverse reactions in recipients of potentially contaminated units. Efforts also should be also directed to identify blood donors with significant risk of bacteremia, at the time of donation in the first place as a high priority. The goal of this review is to highlights strategies for identifying both the sources of bacterial contamination of blood components in Norway and identifying donors with a higher risk of bacteremia at the time of donation. The key to achieving this goal is initiating continual revising and upgrading the Norwegian transfusion guidelines, based on the transfusion legislation and by introducing a relevant specialized donor bacterial questionnaire.     

Transfusion-transmitted bacterial infectionin the United States, 1998 through 2000

BACKGROUND: Bacterial contamination of blood components can result in transfusion-transmitted infection, but the risk is not established. STUDY DESIGN AND METHODS: Suspected cases of transfusion-transmitted bacteremia were reported to the CDC by participating blood collection facilities and transfusion services affiliated with the American Red Cross, AABB, or Department of Defense blood programs from 1998 through 2000. A case was defined as any transfusion reaction meeting clinical criteria in which the same organism species was cultured from a blood component and from recipient blood, with the organism pair confirmed as identical by molecular typing. RESULTS: There were 34 cases and 9 deaths. The rate of transfusion-transmitted bacteremia (in events/million units) was 9.98 for single-donor platelets, 10.64 for pooled platelets, and 0.21 for RBC units; for fatal reactions, the rates were 1.94, 2.22, and 0.13, respectively. Patients at greatest risk for death received components containing gram-negative organisms (OR, 7.5; 95% CI, 1.3-64.2; p = 0.009). CONCLUSION: Bacterial contamination of blood is an important cause of transfusion-transmitted infection; infection risk from platelet transfusion is higher compared with that from RBCs, and, overall, the risk of infection from bacterial contamination now may exceed that from viral agents. Recipients of components containing gram-negative organisms are at highest risk for transfusion-related death. The results of this study may help direct efforts to improve transfusion-related patient safety.     

The role of photochemical treatment with amotosalen and UV-A light in the prevention of transfusion-transmitted cytomegalovirus infections

Primary cytomegalovirus (CMV) infection is usually asymptomatic in immunocompetent patients but can cause serious life-threatening complications in immunocompromised CMV-seronegative patients, including patients receiving a bone marrow or peripheral blood stem cell transplant, recipients of some solid-organ transplants, and low-birth-weight neonates. Current recommendations for preventing transfusion-transmitted CMV (TT-CMV) infection in these patients include exclusive use of CMV-seronegative and/or leukoreduced cellular blood components (red blood cells and platelets) for transfusion. However, breakthrough cases of TT-CMV still occur. Despite improving the safety of blood components, testing remains a reactive approach to blood safety. In contrast, pathogen inactivation technologies offer a proactive approach with the potential to further improve blood safety. To reduce the risks associated with platelet transfusions, a photochemical treatment (PCT) process using a combination of the psoralen amotosalen HCl and long-wavelength UV light has been developed and introduced into clinical practice in Europe. PCT has been shown to result in greater than 5.9-log reductions in infectivity of human CMV in platelet concentrates and to prevent the transfusion transmission of murine CMV in a mouse transfusion model. Thus, PCT pathogen inactivation may play a role in further reducing the incidence of TT-CMV infection in patients who are at risk for serious CMV disease. Because PCT is a technology that targets nucleic acids, it also offers a proactive process for the inactivation of a broad range of viral, bacterial, and protozoan pathogens in addition to CMV.     

Bacterial contamination of random-donor platelets in a university hospital in the midwestern region of Brazil

BACKGROUND: Bacterial blood contamination was probably the first recognized transfusion-transmitted disease. Although the transfusion-associated bacterial sepsis has been known for a long time, it remains an important health problem. At present it is the most frequently reported cause of infectious transfusion-related fatalities. The aims of the study were to determine the prevalence of microbiologic contamination in random-donor platelets (RDPs) and to identify the isolated microorganism obtained from a Brazilian university hemotherapy service. STUDY DESIGN AND METHODS: A total of 2000 RDPs were analyzed from November 2004 to June 2005. The time of storage of the platelet (PLT) concentrates studied ranged from the day of donation (Day 0) to the fifth day of storage (Day 5). The RDP cultures were initially performed in pools with bottles containing brain heart infusion (BHI) growth medium, and cultures were incubated aerobically at 37 degrees C for up to 7 days and subcultured onto chocolate agar at 37 degrees C for 48 hours under conditions of microaerophilia. In the cases of positivity of one pool, the culture was individually performed for all the samples of that pool. RESULTS: Eight units (0.4%; 95% confidence interval, 0.31-0.49) were found to be contaminated. Isolated microorganisms were three Acinetobacter lwoffii, one Enterobacter intermedium, one Serratia phymuthica, one Staphylococcus haemolyticus, one Staphylococcus hominis, and one Bacillus sp. CONCLUSION: PLT concentrates were contaminated with bacteria in 0.4 percent of tested units, which represents a potential risk to patients and a public health problem. Regarding the contaminant microorganisms, a predominance of Gram-negative agents was observed (62.5%).