Effects of white cell reduction on the resistance of blood components to bacterial multiplication

Growth and Distribution of Bacteria in Contaminated Whole Blood and Derived Blood Components

Introduction

Bacterial contamination of blood products presumably occurs mainly during blood collection, starting from low initial concentrations of 10-100 colony-forming units (CFUs) per bag. As little is known about bacterial growth behavior and distribution in stored whole blood (WB) and WB-derived blood products, this study aims to provide data on this subject.

Methods

WB units were inoculated with transfusion-relevant bacterial species (Acinetobacter baumannii, Bacillus cereus, Escherichia coli, Klebsiella pneumoniae, Listeria monocytogenes, Pseudomonas fluorescens, Serratia marcescens, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus dysgalactiae, Streptococcus pyogenes, Yersinia enterocolitica; n = 12 for each species), stored for 22-24 h at room temperature, and then centrifuged for separation into plasma, red blood cells (RBCs), and buffy coats (BCs). The latter were pooled with 3 random donor BCs and one unit of PAS-E each to yield plasma-reduced platelet concentrates (PCs). Samples for bacterial colony counting were collected after WB storage and immediately after blood component production. Sterility testing in PCs (n = 12 for each species) was performed by bacterial culture after 7 days of storage.

Results

Bacterial growth in WB varied remarkably between donations and species. Streptococcus species produced the highest titers in WB, whereas Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, and Pseudomonas fluorescens did not multiply. Centrifugation resulted in preferential accumulation of bacteria in BCs, with titers of up to 3.5 × 103 CFU/mL in BCs and up to ≤0.9 × 103 CFU/mL in BC-derived PCs. Overall, 72/144 PCs (50%) tested positive for bacteria after storage. Sterility test results were species-dependent, ranging from 12 of 12 PCs tested positive for Streptococcus pyogenes to 1 of 12 PCs positive for Escherichia coli. Bacterial contamination of RBC and plasma units was much less common and was associated with higher initial bacterial counts in the parent WB units.

Conclusions

Bacterial growth in WB is species-dependent and varies greatly between donations. Preferential accumulation of bacteria in BCs during manufacturing is a critical determinant of the contamination risk of BC-derived pooled PCs.

Effect of leukoreduction and temperature on risk of bacterial growth in CPDA-1 whole blood: A study of Escherichia coli

BACKGROUND

Collection of non-leukoreduced citrate-phosphate-dextrose-adenine (CPDA-1) whole blood is performed in walking blood banks. Blood collected under field conditions may have increased risk of bacterial contamination. This study was conducted to examine the effects of WBC reduction and storage temperature on growth of Escherichia coli (ATCC® 25922™) in CPDA-1 whole blood.

METHODS

CPDA-1 whole blood of 450 ml from 10 group O donors was inoculated with E. coli. Two hours after inoculation, the test bags were leukoreduced with a platelet-sparing filter. The control bags remained unfiltered. Each whole blood bag was then split into three smaller bags for further storage at 2-6°C, 20-24°C, or 33-37°C. Bacterial growth was quantified immediately, 2 and 3 h after inoculation, on days 1, 3, 7, and 14 for all storage temperatures, and on days 21 and 35 for storage at 2-6°C.

RESULTS

Whole blood was inoculated with a median of 19.5 (range 12.0-32.0) colony-forming units per ml (CFU/ml) E. coli. After leukoreduction, a median of 3.3 CFU/ml (range 0.0-33.3) E. coli remained. In the control arm, the WBCs phagocytized E. coli within 24 h at 20-24°C and 33-37°C in 9 of 10 bags. During storage at 2-6°C, a slow self-sterilization occurred over time with and without leukoreduction.

CONCLUSIONS

Storage at 20-24°C and 33-37°C for up to 24 h before leukoreduction reduces the risk of E. coli-contamination in CPDA-1 whole blood. Subsequent storage at 2-6°C will further reduce the growth of E. coli.

Efficiency of riboflavin and ultraviolet light treatment against high levels of biofilm-derived Staphylococcus epidermidis in buffy coat platelet concentrates

BACKGROUND AND OBJECTIVES

Staphylococcus epidermidis forms surface-attached aggregates (biofilms) in platelet concentrates (PCs), which are linked to missed detection during PC screening. This study was aimed at evaluating the efficacy of riboflavin-UV treatment to inactivate S. epidermidis biofilms in buffy coat (BC) PCs.

MATERIALS AND METHODS

Biofilm and non-biofilm cells from S. epidermidis ST-10002 and S. epidermidis AZ-66 were individually inoculated into whole blood (WB) units (~10⁶ colony-forming units (CFU)/ml) (N = 4-5). One spiked and three unspiked WB units were processed to produce a BC-PC pool. Riboflavin was added to the pool which was then split into two bags: one for UV treatment and the second was untreated. Bacterial counts were determined before and after treatment. In vitro PC quality was assessed by flow cytometry and dynamic light scattering.

RESULTS

Bacterial counts were reduced during BC-PC production from ~10⁶ CFU/ml in WB to 10³ -10⁴ CFU/ml in PCs (P < 0·0001). Riboflavin-UV treatment resulted in significantly higher reduction of S. epidermidis AZ-66 than strain ST-10002 (≥3·5 log reduction and 2·6-2·8 log reduction, respectively, P < 0·0001). Remaining bacteria post-treatment were able to proliferate in PCs. No differences in S. epidermidis inactivation were observed in PCs produced from WB inoculated with biofilm or non-biofilm cells (P > 0·05). Platelet activation was enhanced in PCs produced with WB inoculated with biofilms compared to non-biofilm cells (P < 0·05).

CONCLUSION

Riboflavin-UV treatment was similarly efficacious in PCs produced from WB inoculated with S. epidermidis biofilm or non-biofilm cells. Levels of biofilm-derived S. epidermidis ≥10³ CFU/ml were not completely inactivated; however, further testing is necessary with lower (real-life) bacterial levels.

Bacterial survival and distribution during buffy coat platelet production

BACKGROUND AND OBJECTIVES

At Canadian Blood Services, buffy coat (BC) platelet concentrates (BC-PCs) show a generally lower bacterial contamination rate than apheresis PCs. This study investigated whether the PC production method contributes to this observation.

MATERIALS AND METHODS

Whole blood (WB) inoculated with eight bacterial strains was processed using the BC method. Bacteria were enumerated throughout BC-PC production and subsequent PC storage. Endotoxin production and bacterial adhesion to PC bags were evaluated during PC storage. PC quality was monitored by CD62P expression (flow cytometry) and changes in dynamic light scattering (ThromboLUX^® ).

RESULTS

During overnight WB hold, Staphylococcus epidermidis titres remained unchanged, commercial Escherichia coli and Klebsiella pneumoniae were eliminated and the remaining organisms proliferated to high concentrations. Through BC-PC production, bacteria segregated preferentially towards the cellular fractions compared to plasma (P < 0·05). During PC storage, most bacteria adhered to the PC bags and Gram negatives produced clinically significant endotoxin levels. Changes in CD62P expression or ThromboLUX scoring did not consistently reflect bacterial contamination in BC-PCs.

CONCLUSION

WB hold during BC-PC production does not have a broad-spectrum bactericidal effect, and therefore, other factors contribute to low rates of contamination in BC-PCs.

Pooled platelet product using the Acrodose plus system: evaluation of feasibility, safety and efficacy

BACKGROUND

Pooling of whole blood-derived platelets is not practiced in India. Currently available data shows that pooled platelets are equivalent in quality and less costly when compared with apheresis platelets.

AIM

To evaluate feasibility, safety and efficacy of pooled platelets using the Acrodose Plus system.

MATERIAL AND METHODS

Standardization of platelet pooling procedure was done. Sterile docking device was used to maintain closed system. Pools of ABO compatible platelets (N=40) as well as ABO incompatible (N=10) pooled platelets were studied. ABO antibody titers were studied before and after pooling in case of ABO incompatible platelet pools. Corrected count increments (CCIs) (at 1h and 24h) were noted after transfusion of pooled platelets and Apheresis platelets in matched patient groups.

RESULTS

Loss of platelet product due to pooling and leucodepletion was not statistically significant (p=0.23). Leucodepletion >3 log was achieved in all pooled platelets. The total platelet content, time taken for procedure and pH were within acceptable limits. There were no issues related to platelet availability and turn around time during the study period. There was a reduction in the ABO antibody titers after pooling in case of the ABO incompatible pools. None of the pooled platelets showed evidence of bacterial contamination on testing with eBDS system at 18 h and 24h intervals after pooling. CCI with pooled platelets was equivalent to that with apheresis platelets at 1h (p=0.36) and 24h (p=0.15).

CONCLUSION

Whole blood derived platelets can be pooled safely using closed system without altering the platelet quality in vitro as well as in vivo survival post transfusion. Pooled platelets can be a cost effective and safe alternative to thrombocytopenic patients whose transfusion requirements cannot be fulfilled with apheresis platelets alone.

Routine use of a rapid test to detect bacteria at the time of issue for nonleukoreduced, whole blood-derived platelets

BACKGROUND

The Pan Genera detection (PGD) test is used to screen platelet (PLT) products for bacterial contamination. We report the experience of using the PGD test on whole blood-derived PLTs (WBPs) at two large centralized transfusion services (CTS).

STUDY DESIGN AND METHODS

Records of PGD test results were retrospectively reviewed. The PGD test was performed on individual WBP units or pools of WBPs ranging in size from 2 to 6 units at the time of issue. Bacterial culture was performed on PLT products with positive PGD tests, and at one CTS, the available cocomponents.

RESULTS

A total of 70,561 WBP pools were screened with the PGD test. There were seven true-positive PGD tests and 242 false-positive tests (positive predictive value of PGD test, 2.81%). The overall contamination rate was 99 per 10(6) WBP pools (1:10,080; 95% confidence interval [CI], 40-204), and the false-positive rate was 3430 per 10(6) WBP pools (1:292; 95% CI, 3011-3890). All seven bacterial isolates were Gram positive. The median age of the individual WBP units in the seven contaminated pools was 5 days (range, 3-5 days) compared to 4 days (range, 1-5 days) in the false-positive pools (p=0.0012). The same bacteria isolated from a positive PLT pool also grew in one red blood cell cocomponent.

CONCLUSION

After testing more than 70,000 WBP pools at two large CTSs, the rate of contaminated WBP pools detected by the PGD test was 99 per 10(6) pools (1:10,080).

Bacterial contamination of blood products at the Croatian Institute of Transfusion Medicine: results of eleven-year monitoring

OBJECTIVES

The aim of this study is to present the results and experiences of the Croatian Institute of Transfusion Medicine (CITM) in blood product testing for the presence of bacterial contamination. This is the first study analysing the results of bacterial testing of blood products in Croatia.

METHODS

Results of monitoring blood products for the presence of bacterial contamination during an 11-year period (2000-2010) were retrospectively analysed. As universal screening of platelet concentrates for bacterial contamination is not mandatory in Croatia, the results presented refer to the products tested within the frame of statistical process control.

RESULTS

A total of 23,130 blood products were tested during the study period. There were 122 (0·53%) initially positive and 41 (0·18%) confirmed positive blood products, whereas suspicion of bacterial contamination could be neither confirmed nor ruled out in 8 (0·03%) blood products. While the frequency of bacterial contamination of plasma products was very low (0·03%), there was no statistically significant difference between bacterial contamination of platelet concentrates (0·26%) and RBC concentrates (0·20%). There were 73 (0·32%) false-positive blood products, with nearly equal proportion of causes related to laboratory contamination (n = 34; 0·15%) and those related to the testing system (n = 39; 0·17%).

CONCLUSION

The results obtained in the study did not differ significantly from literature data. A number of measures to reduce the risk of bacterial contamination of blood products have been implemented at CITM. The introduction of universal screening of platelet concentrates for the presence of bacterial contamination should be taken into consideration.

Effect of Safety Measures on Bacterial Contamination Rates of Blood Components in Germany

SUMMARY: Requirements for bacterial testing of blood components on a defined quantity as part of routine quality control were introduced in Germany by the National Advisory Committee Blood of the German Federal Ministry of Health in 1997. The philosophy was to establish standardized methods for bacterial testing. Numerous measures to reduce the risk of bacterial contamination were implemented into the blood donation and manufacturing processes between 1999 and 2002. German Blood establishments performed culture-based bacterial testing on random samples of platelet concentrates (PCs), red blood cells (RBCs) and fresh frozen plasma (FFP) and reported data out of the production periods 1998, 2001 and 2005/2006. While the bacterial contamination rate of apheresis PCs remained nearly unchanged, it decreased by 70% for pooled PCs to a rate of 0.158% in the last observation period. Leukocyte-depleted RBCs with diversion of the initial blood volume showed a contamination rate of 0.029% which is significantly lower than that of RBCs without leukocyte depletion and diversion (0.157%). The contamination rate of plasma decreased by 80%. Preventive measures resulted in a significant reduction of bacterial contamination of blood components. Long-term monitoring with standardized methods for bacteria testing supports evaluation of the cumulative effect of contamination reducing measures.

Gewinnung, Herstellung und Lagerung von Blut und Blutkomponenten

Blutspender leisten einen wertvollen Dienst für die Gemeinschaft: Die ständige Verfügbarkeit von Blutkomponenten ist zur unverzichtbaren Voraussetzung für viele Bereiche der Medizin geworden. Nicht nur die Gewinnung und Aufarbeitung von Blut und Blutbestandteilen zur Sicherstellung einer qualitativ wie quantitativ guten Versorgung, sondern auch die kompetente Betreuung der Spender ist eine der großen Aufgaben der Transfusionsmedizin.

Elimination and multiplication of bacteria during preparation and storage of buffy coat-derived platelet concentrates

BACKGROUND

The prevalence of bacterial contamination of random-donor platelet concentrates (PCs) is considerably lower than that of blood donations. Which key steps of the preparation procedure contribute to the elimination of bacteria was investigated.

STUDY DESIGN AND METHODS

Ten bacteria species were used. Blood donations were spiked with bacteria and stored at 22 degrees C for 8 hours. The buffy coats were kept for 6 hours. PCs were prepared from pools of 4 buffy coats. At each preparation step and during PC storage, bacteria contents were measured. In additional experiments, the titers of spiked blood and buffy coats were determined after storage at 20, 22, or 24 degrees C for 8 and up to 24 hours, respectively.

RESULTS

Enterobacter cloacae, Escherichia coli, Pseudomonas aeruginosa, Serratia marcescens, and Yersinia enterocolitica were completely inactivated during storage in blood or buffy coats. Titer reduction was between 3.32 and 4.62 log. Bacillus cereus, Propionibacterium acnes, Staphylococcus aureus, and Staphylococcus epidermidis did not multiply. Compared with their values in spiked blood the titers in the PCs were reduced by 1.7 to 2.8 log. Klebsiella pneumoniae was the only species that grew in blood. With the exception of P. acnes, those species that were not removed by the preparation process multiplied in the PCs. Remarkable donor-to-donor variations of the bactericidal activities of buffy coats were detected when the storage time was prolonged to 24 hours.

CONCLUSIONS

Bacteria are significantly eliminated by the preparation procedure for random donor PCs. Also, blood and buffy coats are bactericidal for most species. When buffy-coat storage is prolonged, it cannot, however, be predicted whether specific strains vanish or multiply.

Leucodepletion and Blood Products

BACKGROUND

Leucoreduction of blood products is increasingly being employed to produce blood products with residual WBCs < 5 × 10(6) per unit (99.9 percent or a log 3 leucoreduction). Clinical data suggests that non-haemolytic febrile transfusion reactions can be prevented by leucodepletion. The procedure also prevents alloimmunisation to HLA antigens in patients who will repeatedly require transfusion of blood/blood products.

METHOD

Of the methods available to reduce the number of WBC in blood products washing of red cells, freezing and deglycerolisation are effective and yield a product with only a 24 hour shelf life. Other methods such as leucodepletion filters are relatively inexpensive, simple and the final product has a normal shelf life. Modern generation of leucoreduction filters and apheresis machines can provide greater than 4 log reduction of WBC.

RESULTS

After the introduction of leucodepletion of blood for Thalassemics at our center in 2003, the incidence of non haemolytic febrile transfusion reactions (NHFTR) fell from 4% in 2002 to 1% in 2003.

CONCLUSION

In patients undergoing long-term blood transfusion therapy e.g. Thalassemics, alloimmunisation against the HLA antigens on donor white cells is prevented by leucodepletion and prevents NHFTRs.

Influence of blood prestorage conditions and white blood cell filtration on the bacterial load of blood deliberately inoculated with Gram-positive and Gram-negative pathogens

BACKGROUND AND OBJECTIVES

Currently, the bacterial contamination of blood constitutes one of the major infectious risks of transfusion. The aim of this study was to evaluate the bactericidal effect of blood on various bacterial species and to determine the influence of prestorage conditions and white blood cell (WBC) filtration on the reduction of the bacterial load in isolated red blood cells (RBCs).

MATERIALS AND METHODS

The growth kinetics of eight different species of bacteria were studied at 20 degrees C in deliberately contaminated RBC units. Further experiments evaluated the effect of prestorage conditions and WBC filtration on the viability of two model bacteria (Klebsiella oxytoca and Staphylococcus epidermidis) in comparison to previous results obtained with Yersinia enterocolitica.

RESULTS

For bacteria susceptible to the bactericidal effect of blood (mainly Gram-negative rods), a reduction of the bacterial load was obtained within 2 h of prestorage at 20 degrees C. When the prestorage period was prolonged beyond 3 h at 20 degrees C, rapid growth was observed with some Enterobacteriaceae. Whereas WBC filtration reduced dramatically the viability of Y. enterocolitica, it had only a minimal effect on the viability of S. epidermidis and K. oxytoca. However, the two latter species of bacteria did not survive prolonged storage at 4 degrees C.

CONCLUSIONS

Experiments conducted under realistic conditions are needed to determine whether it would be worthwhile recommending the rapid storage of RBCs at 4 degrees C after WBC reduction of the blood product.

Bacterial contamination in blood components and preventative strategies: an overview

Bacterial contamination of blood and its cellular components remains an unresolved problem in transfusion medicine and is considered to be the most common microbiological cause of transfusion associated morbidity and mortality. This is because contaminated units may contain large numbers of virulent bacteria as well as endotoxins that are considered to be fatal to the recipient. Accordingly, measures have been proposed to prevent or at least control the potential risk of transfusion associated bacteria infections. Broadly, these approaches include: bacterial avoidance; bacterial growth inhibition and bacterial load reduction by leucofiltration/viral inactivation. Unfortunately, none of the current approaches alone or in combination have received overall acceptance in terms of operational practice and safety/efficacy. Considerable effort has also been directed towards improving bacterial detection in order to provide a scientific basis for the lengthening of the shelf life of liquid stored platelets, without affecting, to a large extent their safety/efficacy. These issues have been highlighted in this overview on the current status and future trends.

Inactivation of pathogens in platelet concentrates by using a two-step procedure

BACKGROUND AND OBJECTIVES

Platelet concentrates are contaminated with residual leucocytes and may also be infected with viruses and bacteria. We investigated whether these pathogens can be inactivated by a two-step procedure comprising photodynamic treatment in the presence of the phenothiazine dye, thionine, followed by irradiation with ultraviolet light (UV-B, wavelength range 290-330 nm).

MATERIALS AND METHODS

Platelet concentrates were prepared from buffy coats. The concentrates were spiked with different viruses, bacteria and leucocytes, then illuminated with yellow light in the presence of thionine at dye concentrations between 1 and 5 microm and with UV-B at doses up to 2.4 J/cm2. The infectivity of samples and the viability of leucocytes were assayed before and after treatment. The influence of treatment on in vitro platelet function was also examined.

RESULTS

The inactivation of free viruses in platelet concentrates by photodynamic treatment with thionine/light was significantly enhanced when it was followed by irradiation with UV-B. The inactivation of leucocytes and of bacteria by UV-B was improved when it was preceded by thionine/light. Sterile platelet concentrates were prepared from buffy coats infected with Staphylococcus epidermidis. Platelet function and the storage stability of platelet concentrates were only moderately influenced by the two decontamination steps.

CONCLUSIONS

Photodynamic treatment in the presence of the phenothiazine dye, thionine, followed by low-dose UVB, has the potential to inactivate viruses, leucocytes and bacteria, which might contaminate platelet concentrates. Both treatments complement each other.

Reduction of Yersinia enterocolitica load in deliberately inoculated blood: the effects of blood prestorage temperature and WBC filtration

BACKGROUND

Yersinia enterocolitica is known to cause severe infections in patients who receive transfusions.

STUDY DESIGN AND METHODS

The aim of the study was to define the best strategy for reducing the bacterial load in blood that was deliberately contaminated with Y. enterocolitica by combining prestorage temperature and WBC filtration with conditions of blood processing close to those applied in blood banks.

RESULTS

The effects of three prestorage temperatures (4 degrees C, 20 degrees C, 37 degrees C) were evaluated at various times after infection. The best reduction of bacterial load was achieved after 3 hours at 20 degrees C. In further experiments, conducted according to the former specifications, filtration of whole blood from eight and six donors with an inoculum of 100 and 500 to 1000 CFUs per mL, respectively, resulted in a total inhibition of bacterial growth up to 42 days after infection. After fractionation of blood components, in contrast to plasma and RBCs, filtration was shown to reduce dramatically the bacterial growth in buffy coats, demonstrating that the antibacterial effect of filtration was supported by the removal of infected WBCs from blood samples.

CONCLUSION

These results provide support for the systematic use of blood filtration in the preparation of blood components to prevent Y. enterocolitica infection of patients receiving transfusions.

Transfusion-related bacterial sepsis

Transfusion-associated bacterial sepsis is a persistent problem in transfusion medicine, posing a greater threat than the combined risks of receiving a blood product contaminated with HIV-1 or 2, hepatitis C virus (HCV), hepatitis B virus (HBV), and human T-cell lymphtrophic virus (HTVL) -I or -II. This article provides a brief overview of the current incidence, clinical presentation, associated blood products and organisms, and the most feasible and effective methods available to reduce the potential risk of transfusion-associated sepsis. Because bacterial contamination of blood products is the most frequent cause of transfusion-transmitted infectious disease, and as no single existing strategy can completely eliminate its risk, it is important that clinical suspicion be high, and any partial solutions additively be implemented.

WBC reduction in RBC concentrates by prestorage filtration: multicenter experience

BACKGROUND

As universal leukocyte (WBC) reduction (ULR) is being considered as a new standard, few data are available on the performance of WBC-reduction filtration in routine practice. The performance of WBC-reduction in RBCs, using varied filtration practices, in meeting the current FDA requirement (<5 x 10(6)), Council of Europe (EC) recommendation, the proposed FDA requirement (<1 x 10(6)), and a more stringent proposal (<5 x 10(5)) for residual WBCs per RBC unit was assessed and compared.

STUDY DESIGN AND METHODS

Participating facilities were the 11 sites of the Viral Activation Transfusion Study (VATS), a prospective study of the impact of transfusion with and without WBC-reduction on survival and HIV viral load in HIV-1-infected patients. Patients randomly assigned to undergo WBC reduction were required to receive RBCs < or =14 days old that had undergone prestorage (within 72 hours of collection) WBC-reduction filtration by a method devised to achieve a postfiltration WBC count of <5 x 10(6). Residual WBC quantitation was performed by PCR in the central VATS laboratory by using frozen WBC-reduced RBC samples obtained at issue for transfusion.

RESULTS

A total of 1869 WBC-reduced RBC units were studied. Filtration practices varied within and between sites. There were significant differences in mean residual WBC counts at the 11 sites (p<0.001). Among the WBC-reduced RBC units, 0.8 percent exceeded 5 x 10(6) WBCs per unit, 8.3 percent exceeded 1 x 10(6) WBCs per unit, and 14.3 percent exceeded 5 x 10(5) WBCs per unit.

CONCLUSION

Residual WBCs in WBC-reduced RBC units vary within and between sites. WBC reduction was successful, in that over 99 percent and 91 percent of VATS WBC-reduced RBC units met US and EC thresholds, respectively. However, the small but measurable failure rate indicates that not every unit will meet these guidelines.

Efficacy of a new collection procedure for preventing bacterial contamination of whole-blood donations

BACKGROUND

Transfusion-related bacterial contamination is a serious problem. The introduction of bacteria into donations at the collection stage seems frequent, despite well-conducted phlebotomy site preparation. Additional preventive measures are required.

STUDY DESIGN AND METHODS

The aim of this study was to assess the potential efficacy of excluding the first 15 mL of blood to reduce the bacterial contamination of donations. A special device allowed the aseptic collection of two samples at the beginning of donation: S1 (first 15 mL) and S2 (next 15 mL). Bacteriologic cultures of S1 and S2 were performed by using an automated system. The procedure's efficacy was measured by the proportion of positive donations in S1 that were then negative in S2.

RESULTS

S1 and/or S2 were positive in 76 (2.2%) of 3385 donations. In about three-fourths of the culture-positive donations, contamination was detected in the first 15-mL sample only. Gram-positive cocci accounted for 81 percent of species, gram-positive bacilli for 14 percent, and gram-negative bacilli for 5 percent. The new procedure would have prevented the introduction of bacteria in 55 donations, reducing to 0.6 percent the risk of contamination from the first 15 mL collected.

CONCLUSION

Although the final effect on blood component bacterial contamination rates cannot be derived from the study, excluding the first 15 mL of blood may reduce the rate of bacterial contamination in donations.

Bacterial decontamination of blood stem cell apheresis products

High-dose chemotherapy using autologous bone marrow or mobilized blood as the source of stem cells for haematologic rescue, is being widely used for a variety of haematological malignancies and solid tumours. To collect sufficient numbers of haematopoietic stem cells for successful engraftment, standard apheresis procedures are performed. Newer techniques and refinements of the procedure allow using only 1 to 2 apheresis products (AP) for autografting. Bacterial contamination of the AP, although very rare, sometimes occurs and may lead to generalized infection in the recipient. The apheresis must be repeated, sometimes even including time-consuming and costly mobilization. At our institution, the patients' blood stem cells are usually mobilized with chemotherapy followed by daily s.c. haematopoietic growth factor injections or with growth factor alone. An apheresis machine is used for collection through a central venous line and the AP is routinely checked for bacterial contamination. Results are only available after the product has been processed and cryopreserved. In the last 5 years, we observed bacterial contamination in four of our AP. Therefore, we investigated the possibility of in vitro antibiotic decontamination. Using standard antibiograms, we determined the sensitivities of the contaminating bacteria. By incubating the products with the specific antibiotics at bactericidal concentrations, we were able to sterilize the probes from the contaminating bacteria. In the concurrently performed controls without the active substance, bacteria were still detectable. We conclude that in selected cases, in vitro decontamination using pretested antibiotics, may be a feasible, cost-effective, and easy alternative to performing additional apheresis procedures.

In vitro and in vivo properties of various types of platelets

The most popular procedures used to prepare platelet concentrates (PC) can be categorized into methods using platelet rich plasma (PRP) obtained by soft centrifugation of whole blood units, methods using buffy coats (BC) obtained by hard centrifugation of whole blood units, and apheresis procedures. The main feature that differentiates apheresis PC from whole blood unit derived PC is that apheresis reduces the number of donors necessary to support a recipient, although the advantages related to this feature have not been conclusively documented. From the biochemical point of view, a limited number of comparative studies and a large series of non-comparative studies indicate that differences in PC obtained with different protocols depend more on the performances of the production laboratory rather than the preparative approach--PRP, BC or apheresis--itself. Similarly, the clinical effectiveness of PC seems to depend more on PC age, storage modalities and recipient's conditions rather than primarily on the method of PC preparation. Despite the basic differences in the three preparative approaches, all methods share a number of key elements that are necessary pre-requisites for a successful platelet transfusion therapy: minimization of the risk of bacterial contamination by careful donor skin disinfection and temperature control during PC production and storage; protection of aerobic metabolism during PC storage; laboratory quality control including at least pH and volume determinations, platelet and white cell counts and visual inspection of the swirling phenomenon at time of release. Future directions in the field of PC production include the development of new products such as infusible platelet membranes, thrombospheres, thromboerythrocytes and reconstituted freeze-dried platelets.

What's new in transfusion medicine?

The safety of the blood supply has increased tremendously in the past decade. Donor screening and improved infectious disease testing of units for transfusion have contributed to the decreased risk of transfusion-transmitted diseases. Reduction of the number of passenger leukocytes from RBC and platelet transfusions decreases the rate of febrile transfusion reactions and alloimmunization. Irradiation of cellular products helps prevent TA-GVHD. The practice of obtaining an informed consent prior to transfusion helps patients and families understand the risks and benefits of and alternatives to transfusion therapy.

[Quality assurance of bacterial incidents associated with blood transfusion]

Transfusion associated bacterial sepsis, TABS, may be caused by-donor bacteremia,-bacteria from the donors skin,-bacteria brought by one of the persons handling the donation or the blood product, from collection and components preparation to the actual transfusion,-or bacteria introduced by a defect in one of the disposables used. Quality Assurance relies on the Good Transfusion Practices of the French Blood Agency all along the transfusion chain from the donor to the recipient. Active involvement of personnel, standardisation and controls as well as improvement of technics particularly as regarding donor selection, skin disinfection technics and collection are required. The ultimate control is hemovigilance with proper identification and investigation of all cases of TABS even with mild symptoms. Centralisation of data in the Haemovigilance scheme is a further step toward a better understanding and improvement of blood products bacterial security.