Multivariate analysis of determinants of bacterial contamination of whole-blood donations

Platelet Additive Solutions and Pathogen Reduction Impact on Transfusion Safety, Patient Management and Platelet Supply

Since 1998, leuko-reduction is used in France for all platelet concentrates (PCs), apheresis-derived (APCs) and pooled whole blood-derived buffy-coats (BCPCs). Platelet additive solutions (PAS), introduced in 2005, accounted for over 80% of the platelet supply from 2011 to 2017. The Intercept pathogen reduction technology (PR), started in a pilot study in 2007, was generalized in 2018. Between 2007 and 2021, the use of BCPCs increased steadily from 23% to 70% of the supply. Objectives: to analyze the impact of these modifications on adverse transfusion reactions (ATRs), patient management and blood transfusion organization. Results: The overall incidence of ATRs /105 PCs is significantly lower with PAS- and PR-PCs as compared to PCs in plasma (PL), with the decreasing hierarchy PL > PAS > PR. PAS- and PR-PCs lead to significantly lower incidences of allergy and alloimmunization to RBC antigens (RC-AI) ATRs. The incidence of bacteria transmission (TTBI) is significantly reduced by 95% with PR-PCs. APC-related ATR incidence is significantly higher than BCPC for allergy (+233%), TTBI (+100%), APTR (+75%), Major-ABO-II (+65%), HLA/HPA-AI (+38%), FNHTR (+22%), and life-threatening ATRs (+106%). A single diagnosis is significantly less associated with APCs: RC-AI (-47%). The generalization of PR-PCs, which exhibit a lower platelet content than PAS- and PL-PCs, is associated with a significant 9% decrease in the ATR incidence per PC, a 13% increase in the number of PCs transfused per patient, and a nonsignificant 3% increase in the ATR incidence per patient. The outdated PCs percentage declined significantly from 3.7% to 1.7%.

Longitudinal analysis of annual national hemovigilance data to assess pathogen reduced platelet transfusion trends during conversion to routine universal clinical use and 7-day storage

BACKGROUND

France converted to universal pathogen reduced (PR; amotosalen/UVA) platelets in 2017 and extended platelet component (PC) shelf-life from 5- to 7-days in 2018 and 2019. Annual national hemovigilance (HV) reports characterized longitudinal PC utilization and safety over 11 years, including several years prior to PR adoption as the national standard of care.

METHODS

Data were extracted from published annual HV reports. Apheresis and pooled buffy coat [BC] PC use was compared. Transfusion reactions (TRs) were stratified by type, severity, and causality. Trends were assessed for three periods: Baseline (2010-14; ~7% PR), Period 1 ([P1] 2015-17; 8%-21% PR), and Period 2 ([P2] 2018-20; 100% PR).

RESULTS

PC use increased by 19.1% between 2010 and 2020. Pooled BC PC production increased from 38.8% to 68.2% of total PCs. Annual changes in PCs issued averaged 2.4% per year at baseline, -0.02% (P1) and 2.8% (P2). The increase in P2 coincided with a reduction in the target platelet dose and extension to 7-day storage. Allergic reactions, alloimmunization, febrile non-hemolytic TRs, immunologic incompatibility, and ineffective transfusions accounted for >90% of TRs. Overall, TR incidence per 100,000 PCs issued declined from 527.9 (2010) to 345.7 (2020). Severe TR rates declined 34.8% between P1-P2. Forty-six transfusion-transmitted bacterial infections (TTBI) were associated with conventional PCs during baseline and P1. No TTBI were associated with amotosalen/UVA PCs. Infections with Hepatitis E (HEV) a non-enveloped virus resistant to PR, were reported in all periods.

DISCUSSION

Longitudinal HV analysis demonstrated stable PC utilization trends with reduced patient risk during conversion to universal 7-day amotosalen/UVA PCs.

Bacterial contamination of blood products in Africa

BACKGROUND

Bacterial contamination of blood components (notably platelets) remains a leading infectious risk to the blood supply. There has been extensive research in high-income countries to characterize the risk of bacterial contamination along with adoption of strategies to mitigate that risk. By contrast, related data in Africa are lacking.

STUDY DESIGN AND METHODS

An electronic survey was distributed to members of African Society of Blood Transfusion to assess existing or planned measures at African blood centers and hospitals to mitigate bacterial contamination of blood products. A literature review of studies pertaining to related transfusion-associated risk in Africa was conducted to complement the findings.

RESULTS

Forty-five responses were received, representing 16 African countries. All respondents were urban, either in blood centers (n = 36) or hospital-based transfusion services (n = 9). Reported measures included skin disinfection (n = 41 [91.1%]); diversion pouches (n = 14 [31.1%]); bacterial culture (n = 9 [20%]); pathogen reduction (PR) (n = 3 [6.7%]); and point-of-release testing (PoRT) (n = 2 [4.4%]). Measures being considered for implementation included: skin disinfection (n = 2 [4.4%]); diversion pouches (n = 2 [4.4%]); bacterial culture n = 14 (31.1%); PR (n = 11 [24.4%]); and PoRT (n = 4 [8.9%]). Of the 38 respondents who reported collection of platelets, 14 (36.8%) and 8 (21.1%) reported using diversion pouches and bacterial culture, respectively. The literature review identified 36 studies on the epidemiology of bacterial contamination and septic transfusion reactions in Africa; rates of contamination ranged from 0% to 17.9%.

CONCLUSIONS

The findings suggest that prevention of bacterial contamination of blood components and transfusion-associated sepsis in Africa remains neglected. Regional preventive measures have not been widely adopted.

Bacterial contamination of blood products for transfusion in the Democratic Republic of the Congo: temperature monitoring, qualitative and semi-quantitative culture

BACKGROUND

Bacterial contamination of blood for transfusion is rarely investigated in low-income countries. We determined the contamination rate of blood products in the Democratic Republic of the Congo.

MATERIAL AND METHODS

In this prospective observational study, blood products in one rural and two urban hospitals (paediatric and general) contained a satellite sampling bag by which blood was sampled for culture in a blood culture bottle (4 mL) and on an agar-coated slide to estimate colony forming units (CFU/mL). Bacteria were identified with biochemical tests and MALDI-TOF (Bruker). Exposure time >10 °C was assessed on a subset of blood products.

RESULTS

In total, 1.4% (41 of 2,959) of blood products were contaminated with 48 bacterial isolates. Skin (e.g., Staphylococcus spp.) and environmental (e.g., Bacillus spp.) bacteria predominated (97.8% of 45 isolates identified). Bacterial counts were ≤10³ CFU/mL. Contamination rates for the urban paediatric, urban general and rural hospitals were 1.6%, 2.4% and 0.3%, respectively (p=0.004). None of the following variables was significantly associated with contamination: (i) donor type (voluntary 1.6%, family 1.2%, paid 3.9%); (ii) type of blood product (red cells 1.6%, whole blood 0.6%); (ii) season (dry season 2.4%, rainy season 1.8%); (iv) age of blood product (contaminated 8 days vs non-contaminated 6 days); and (v) exposure time >10 °C (median for contaminated and non-contaminated blood reached maximum test limit of 8 hours).

DISCUSSION

A bacterial contamination rate of 1.4% of whole blood and red cells is similar to results from high-income countries. Implementation of feasible risk-mitigation measures is needed.

Evaluation of the Role of Novel Aprotic Dimethyl Sulfoxide in Cutaneous Antisepsis Protocols Prior to Blood Donor Phlebotomy with Isopropyl Alcohol, Povidone Iodine or Chlorhexidine

The study was planned to measure the reduction of the load of bacterial flora on the blood donor's arm quantitatively using a three step protocol of donor arm cleansing incorporating either 70% isopropyl alcohol (IPA) or 5% w/v povidone iodine (PVI, 0.5% w/v available iodine) or 4% chlorhexidine gluconate (CHG) with or without the addition of 5% dimethyl sufloxide (DMSO). Single blind randomized study after obtaining ethical clearance, using the Miles and Misra technique for quantification and matrix assisted laser desorption ionization-mass spectrometry for identification of colony morphotypes on blood donor's skin. The mean pre-cleansing colony forming units (CFUs) was 89,318 and mean post-cleansing CFUs was 132, with a mean reduction of 99.85% with a mean log reduction of 3.24 (95% CI 2.01-4.47) at a P value of <0.0001. The post-cleansing CFUs was reduced to zero in all 34 samples in the protocol using CHG with DMSO, in 23 of 31 samples in the protocol using PVI with DMSO and 19 of 29 samples in the protocol using IPA with DMSO. The difference in means of the reduction of CFUs in protocols using CHG with DMSO compared with protocols using PVI or IPA with DMSO and PVI or IPA without DMSO was statistically significant with P value of 0.006, 0.0009, 0.015 and 0.05 respectively. The enhanced cutaneous antisepsis effect of CHG when complimented with DMSO in presence of IPA using the three step protocol of donor arm cleansing could stimulate more research and utilization of this as an additional safety towards the prevention of the problem of bacterial contamination of blood and blood components.

Cryopreservation in Closed Bag Systems as an Alternative to Clean Rooms for Preparations of Peripheral Blood Stem Cells

Autologous and allogeneic stem cell transplantation (SCT) represents a therapeutic option widely used for hematopoietic malignancies. One important milestone in the development of this treatment strategy was the development of effective cryopreservation technologies resulting in a high quality with respect to cell viability as well as lack of contamination of the graft.Stem cell preparations have been initially performed within standard laboratories as it is routinely still the case in many countries. With the emergence of cleanrooms, manufacturing of stem cell preparations within these facilities has become a new standard mandatory in Europe. However, due to high costs and laborious procedures, novel developments recently emerged using closed bag systems as reliable alternatives to conventional cleanrooms. Several hurdles needed to be overcome including the addition of the cryoprotectant dimethylsulfoxide (DMSO) as a relevant manipulation. As a result of the development, closed bag systems proved to be comparable in terms of product quality and patient outcome to cleanroom products. They also comply with the strict regulations of good manufacturing practice.With closed systems being available, costs and efforts of a cleanroom facility may be substantially reduced in the future. The process can be easily extended for other cell preparations requiring minor modifications as donor lymphocyte preparations. Moreover, novel developments may provide solutions for the production of advanced-therapy medicinal products in closed systems.

[Prevention of bacterial risk: pathogen inactivation/detection of bacteria]

Bacterial contamination of blood products remains the most important infectious risk of blood transfusion in 2013. Platelet concentrates (PC) are in cause in the majority of the transfusion reaction due to bacterial contaminations. A lot of prevention methods have been developed over the last 10 years (pre-donation interview, skin decontamination, diversion of the first 30 mL of the donation, leuko-reduction...), they have focused on limiting the contamination of the donations and prevent the bacterial growth in donations and/or in the blood products. These measures were effective and led to significantly reducing the risk of adverse effects associated with bacterial growth. However, every year there are about six accidents (with a high level of imputability) and one death. The reduction of the bacterial risk remains a priority for the French Blood Establishment (EFS). The procedure for skin disinfection is going to be improved in order to further strengthen this crucial step to avoid the contamination of donation. Methods of pathogen inactivation applied to plasma and PC are available in France and their effectiveness is demonstrated on the bacterial risk. Methods for bacterial detection of PC are used in many countries now. Automated culture is the most common. Alternatives are now available in the form of rapid tests able to analyze the PC just before the delivery and avoid false negatives observed with automated culture. Assessments are under way to confirm these benefits in 2013.

Bacterial contamination of platelet concentrates: results of a prospective multicenter study comparing pooled whole blood-derived platelets and apheresis platelets

BACKGROUND

The GERMS Group initiated a prospective multicenter study to assess prevalence and nature of bacterial contamination of pooled buffy-coat platelet concentrates (PPCs) and apheresis platelet concentrates (APCs) by routine screening with a bacterial culture system.

STUDY DESIGN AND METHODS

In nine centers overall, 52,243 platelet (PLT) concentrates (15,198 APCs, 37,045 PPCs) were analyzed by aerobic and anaerobic cultures (BacT/ALERT, bioMérieux).

RESULTS

In 135 PLT concentrates (PCs; 0.26%), bacteria could be identified in the first culture (0.4% for APCs vs. 0.2% for PPCs; p < 0.001). In 37 (0.07%) of these PC units, the same bacteria strain could be identified in a second culture from the sample bag and/or the PC unit. The rate of confirmed-positive units did not differ significantly between APC (0.09%; 1/1169) and PPC units (0.06%; 1/1544). Bacteria from skin flora (Propionibacterium acnes, Staphylococcus epidermidis) were the most prevalent contaminants. Median times to first positive culture from start of incubation were 0.7 and 3.7 days in aerobic and anaerobic cultures for confirmed-positive units. With a "negative-to-date" issue strategy, most PC units (55%) had already been issued by time of the first positive culture.

CONCLUSION

The rate of confirmed bacterial contamination of PC units was low. Nevertheless, clinicians must be aware of this risk. The risk of bacterial contamination does not warrant universal preference of APCs. It must be questioned whether routine bacterial screening by a culture method can sufficiently prevent contaminated products from being transfused due to the delay until a positive signal in the culture system and due to false-negative results.

[New container of sample: role in the reduction of bacterial contamination of standard platelet units]

BACKGROUND

Bacterial contamination of unstable blood products constitutes today the most frequent infectious risk transmitted by blood transfusion. Platelet concentrates are often incrimineted. As responsible germs are in general of cutaneous origin, a sample procedure with diversion of the first 20 ml during blood donation is studied. The aim of this study is to evaluate the results of this technique on bacterial contamination rate of standard platelet units prepared at the regional blood transfusion center in Casablanca.

STUDY DESIGN AND METHODS

A comparative study of two types of sample pockets is made: 500 Standard Platelet concentrates (CPS) are prepared after collection using standard triple bags (Baxter) (group 1) and 560 pockets of CPS were prepared after collection using triple bags with Sample Diversion Pouch sampling system for elimination of the first 20 ml of donation (Macopharma and Terumo) (group 2). The skin was disinfected in two times with alcohol 70%. The bacteriological study was made in the two groups at the third day of conservation.

RESULTS

Six CPS of group 1 were contaminated, of which five were staphylococci coagulase negative and one bacillus sp. Six CPS of group 2 were contaminated, of which five were staphylococci coagulase negative and one staphylococcus aureus. The bacteria isolated were those of cutaneous flora at 100%. Diversion of first 20 ml of blood donation results in a 16.6% reduction in bacterial contamination of CPS (P>0.05).

CONCLUSION

The non-significant reduction in the prevalence of the bacterial infection of CP formulates the problem of the indication of the sampling devices with derivation of first 20 ml during blood collection.

[Stating technical requirements and deferral criteria for whole blood donation]

Blood donation is framed by regulations whose finality is to guarantee the safety of blood transfusions and to preserve the health of the donors. Each blood donation is preceded by a medical interview which evaluates the aptitude of the donor to support a 400 to 600 mL collection of blood or its components, and checks the absence of exposure to blood-borne diseases. The criteria of exclusion of blood donation are defined on clinical and epidemiologic arguments. The aim of blood donors selection is consisting in managing the residual infectious risk caused by known pathogens, risk related to the window period due to recent contaminations, the absence of technique of pathogens inactivation available for the cellular blood products, and the risk inherent in any production process. Blood donors selection proved to be the only means of reducing the risk of transmission of an emergent agent by blood transfusion.

De la détection bactérienne à l'inactivation des pathogènes

Bacterial contamination of blood components remains the highest infectious risk in blood transfusion, the risk is particularly high when it affects platelet concentrates (PC). In France, the residual risk of transfusion reaction due to bacterial contamination of PC has been decreasing slowly since 1994 but for all severity 1 case occurs with about 25,000 distributed PC and one death occurs with 200,000 distributed units. This reduction of the risk may be due to the measures which were implemented during the last 10 years in order to prevent contamination during donation. Improving strategies for reducing the risks of bacterial contamination is one of the priorities of the French National Blood Transfusion Service (l'Etablissement Français du sang - EFS). The main target remains PC. Bacterial detection or pathogens inactivation are now available and are able to reduce (for detection) or prevent (for inactivation) the occurrence of reaction due to bacterial contamination of PC. Up to now, the choice is in favour of bacterial detection. A national study was carried out in seven regional EFS at the end of 2004. It aims at confirming the feasibility of a systematic bacterial screening of PC before their delivery. The first conclusions show that this screening can be implemented with acceptable modifications in term of platelets availability. We can expect in a next future that new pathogens reduction technique and/or new detection systems will be available, certainly more efficient to prevent reaction due to bacterial contamination. Implementation of actual detection methods is probably a temporary solution.

Vers la détection des bactéries dans les PSL

Bacterial contamination of blood components represents today the highest infectious risk in blood transfusion, the risk is particularly high when it affects platelet concentrates. The prevention methods developed over the past ten years (donor selection, phlebotomy site preparation, first 30 ml diversion, systematic leuko-reduction...) which aimed at limiting the introduction of bacteria in donations and bacterial proliferation, has reduced the risk of transfusion reaction due to the bacterial contamination. Improving strategies for reducing the risks of bacterial contamination is one of the priorities of the French National Blood Transfusion Service (l'Etablissement français du sang - EFS). It is essential to improve existent prevention methods and develop the implication of all the actors (from donation to transfusion) involved in the prevention of this risk. Bacterial detection or pathogens inactivation are now available and are able to reduce (for detection) or prevent (for inactivation) the occurrence of reaction due to bacterial contamination of PC. Up to now, the choice is in favour of bacterial detection. Three methods (BacT/Alert, BioMerieux; eBDS, Pall; ScanSystem, Hemosystem) of detection of bacterial contamination in PC can be generalised now. Adaptations, need for their implementation are acceptable, especially concerning PC availability.

Feasibility of implementing an automated culture system for bacteria screening in platelets in the blood bank routine

Bacterial contamination of blood components is the principal infectious complication linked to transfusion. The aim of the study was to evaluate the applicability of an automated culture system for platelets. 10 141 platelet concentrates were cultured individually and in pools of five on storage days 1 and 7 using Bact/Alert system aerobic bottles. A modified collection bag was used for improved sampling. Five-millilitre samples were cultured at 37 degrees C for 7 days. Only those samples where the same bacteria were identified in reculture were considered true positives (TP). Homogeneity of proportions was tested by Fisher's exact test. The rate of TP was 30 per 100 000 (95% CI, 6.1-86.4) sampling on day 1; 33 per 100 000 (95% CI, 7-96) on day 7; and 40 per 100 000 (95% CI, 1.28-122.4) if the screening was based on taking both samples (day 1 and 7). Only one TP was detected in the pool testing. The time for detection among TPs on day 1 ranged between 30 and 134 h. The system is not considered practical for use as a routine screening method, as the time for detection is too long. Pool testing is insensitive. Faster screening methods or pathogen-inactivation systems are needed.

Blood pack fault monitoring

BACKGROUND AND OBJECTIVES

The National Blood Service (NBS) has recalled blood components as a result of manufacturing faults, or defective blood pack component parts leading to the possibility of an 'open' system. There has been an increase in the complexity of blood packs as a result of leucodepletion, sample diversion and sampling. The NBS implemented a mechanism to collate and analyse blood pack faults as a safety and quality initiative in conjunction with blood pack manufacturers.

MATERIALS AND METHODS

Standard reporting forms were produced and implemented at all Centres. The forms were collated and analysed using statistical analysis software. Control charts were used to identify trends for specific faults, which were resolved with the relevant manufacturer.

RESULTS

The overall defect rate per million for the three main blood pack manufacturers used by the NBS for the respective periods 2001, 2002 and 2003, were as follows: Manufacturer A, 1076, 1396 and 954; Manufacturer B, 1496, 1301 and 2169; and Manufacturer C, 1871, 1253 and 1392.

CONCLUSIONS

Monitoring and analysis of blood pack faults has resulted in the identification and rectification of specific problems associated with blood pack manufacture and use. Close collaboration with manufacturers has enabled effective remedial action. Wider collation of data would provide an early warning of potential areas of concern.

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.

Positively charged porphyrins: a new series of photosensitizers for sterilization of RBCs

BACKGROUND

Photodynamic treatment could be a way to inactivate pathogens in RBCs. The objective of this study was to characterize the virucidal activity and RBC-damaging activity of a series of cationic porphyrins. Using the most efficacious photosensitizer, various in-vitro human RBC quality variables and in-vivo RBC survival in Rhesus monkeys were evaluated.

STUDY DESIGN AND METHODS

RBCs, spiked with 5 log of extracellular VSV, were treated with porphyrins (25 micro mol/L) and red light (100 W/m2) and essayed for virucidal activity. In-vitro RBC quality variables were assessed during 5 weeks of storage in various ASs. In-vivo survival was investigated with autologous RBCs in Rhesus monkeys.

RESULTS

Tri-P(4) was by far the best sensitizer of a series tested, giving the least hemolysis under conditions that resulted in 5 log-kill of extracellular VSV. Under our experimental conditions, the percentage hemolysis in treated cells was 5.1 +/- 1.1 percent after 5 weeks of storage in SAG-M compared to 1.9 +/- 1.1 percent in the untreated control. Storage in AS-3 resulted hemolysis of 2.3 +/- 1.9 percent. With the exception of IgG binding and potassium leakage, RBC quality variables remained unchanged after photodynamic treatment. Addition of reduced glutathione (GSH) during treatment reduced IgG binding. The 24-hour recovery and T50 of treated RBCs in Rhesus monkeys were satisfactory.

CONCLUSION

Porphyrin Tri-P(4) may be a suitable photosensitizer for sterilization of RBCs. However, further exploration to optimize the method is necessary to reach clinically acceptable goals.

Detection of bacterial contamination of platelet components: six years’ experience with the BacT/ALERT system

BACKGROUND

Hemovigilance has shown that bacteria cause more fatalities than other infections together. Surveillance for detection of bacteria in platelets (PLTs) was initiated. Concomitantly, the storage period for PLTs was extended from 5 to 7 days to reduce cost.

STUDY DESIGN AND METHODS

Analysis was performed of all cases of a positive signal in a screening procedure for contaminated PLTs taking into account results of confirmative cultures and results of culture from blood components including bacteria strains. Records were assessed from patients transfused with blood components issued before the screening culture became positive.

RESULTS

Samples were collected from 22,057 PLT units. An initial reaction was seen in 84 (0.38%). Growth was confirmed in 70 of these. Of the associated PLT units, 26 had been issued or outdated at the time when the culture was found to be reactive, in 27 bacteria were found, and in 17 cultures were negative. The bacteria found were mainly from normal skin flora. Sixty-six patients received 75 blood components issued before the screening system alarmed. None of these patients had a transfusion reaction reported. The outdating fell to less than 5 percent.

CONCLUSION

A screening system for detection of bacterial contamination was implemented without increase in cost owing to extension of storage time to 7 days. Transfusion of several contaminated blood components was prevented.

Bacterial contamination of ex vivo processed PBPC products under clean room conditions

BACKGROUND

Patients undergoing high-dose radio- and/or chemotherapy and autologous or allogeneic PBPC transplantation are at high risk for infections owing to profound immunosuppression. In this study, the rate of microbial contamination of ex vivo processed PBPC products was analyzed, comparing preparation under clean room conditions to standard laboratory conditions.

STUDY DESIGN AND METHODS

After implementation of good manufacturing practice conditions in the two participating institutions, the microbial contamination rate of 366 PBPC harvests from 198 patients was determined under certified clean room conditions (Group A) from 2000 until 2002. To investigate influence of improved environmental conditions along with other parameters, this set of samples was compared with a historical control set of 1413 PBPC products, which have been processed ex vivo under a clean bench in a regular laboratory room and were harvested from 626 patients (Group B) from 1989 until 2000.

RESULTS

In Group B microbial contamination was found in 74 PBPC products (5.2%) from 57 patients. In Group A microbial growth was detected in 3 leukapheresis products (0.8%) from 3 patients. After exclusion of PBPC products, which were probably contaminated before manipulation, statistical analysis showed a significant difference (chi2= 10.339; p < 0.001).

CONCLUSION

These data suggest an impact of clean room conditions on the bacterial contamination rate of PBPC products. To identify confounding variables, variables like technique of leukapheresis, culture methodology, and microbial colonization of central venous catheters were taken into account. Further variables might be identified in following studies.

[Transfusion-transmitted bacterial infection: residual risk and perspectives of prevention]

Bacterial contamination of blood components represents today the highest infectious risk of blood transfusion, the risk is particularly high when it affects platelet concentrates. The residual risk of transfusion reaction due to bacterial contamination of platelets concentrates remains stable. For all severity 1 case occurs with 25,000 distributed platelets concentrates and 1 death occurs with 200,000 distributed units. In France, efforts have focused on the prevention of contamination during donation--involving measures such as rejecting the first few millilitres of donated blood and improving skin disinfection--and the prevention of bacterial proliferation in platelets concentrates--notably by removing leukocytes and ensuring high-quality storage of donated blood. Improving strategies for reducing the risks of bacterial contamination is one of the priorities of the French National Blood Transfusion Service (l'Etablissement français du sang-EFS). There is currently considerable debate about the relative importance of bacterial screening methods and methods for inactivating pathogens present in PC. Automated culture (Biomérieux) and the ScanSystem (Hemosystem) and BDS (Pall) method are the most advanced detection systems available, to our knowledge. In term of pathogen inactivation system for platelets, Intercept (Baxter) is nearing the commercial market. These new prevention have logistic and/or functional consequences that will require close scrutiny methods. A national study group is currently considering the consequences of each of these methods and should give its opinion at the end of the first half of 2003.

[Detection of bacterial contamination in platelet concentrates: perspectives]

Bacterial contamination of blood components represents today the highest infectious risk of blood transfusion, the risk is particularly high when it affects platelet concentrates. In France the prevention methods developed over the past six years (donor selection, phlebotomy site preparation, first 30 ml diversion, systematic leuko-reduction...) aimed at limiting the introduction of bacteria in blood and bacterial proliferation. Several methods have been tested for the detection of bacterial contamination in platelet concentrates but none have been generalised. Difficulties were met, due to the necessity of 1) detecting only the platelet concentrates presenting a real infectious risk, when the presence of bacteria is observed in 2.2% (2-4%) of donated blood and 2) guaranteeing the availability of platelet concentrates. New methods have been developed which seem able to bring responses to these difficulties. Several processes are being (or will be) assessed, including automated blood culture, bacterial genomic detection with or without amplification, flow cytometric methods. In parallel, an indirect method able to detect the presence of bacteria, based on oxygen consumption, will also be evaluated. One (or several) of these processes should allow, in the short-term, to detect platelet concentrates presenting an infectious risk. In the future, the interest of bio-chips for bacterial detection in biological fluids must be investigated.