The use of a bacteria detection system to evaluate bacterial contamination in PLT concentrates

Detection of bacterial contamination in platelet concentrates from Brazilian donors by molecular amplification of the ribosomal 16S gene

OBJECTIVE

The aim of our work was to establish a semi-automated high-throughput DNA amplification method for the universal screening of bacteria in platelet concentrates (PCs).

BACKGROUND

Among cases of transfusion transmission of infectious agents, bacterial contamination ranks first in the number of events, morbidity and mortality. Transmission occurs mainly by transfused PCs. Automated culture is adopted by some blood banks for screening of bacterial contamination, but this procedure is expensive and has a relatively long turnaround time.

METHODS

PCs were spiked with suspensions of five different bacterial species in a final concentration of 1 and 10 colony-forming units (CFU) per millilitre. After incubation, the presence of bacteria was investigated by real-time polymerase chain reaction (PCR) and by the Enhanced Bacterial Detection System (eBDS, Pall) assay as a reference method. Real-time PCR amplification was performed with a set of universal primers and probes targeting the 16S rRNA gene. Co-amplification of human mitochondrial DNA served as an internal control.

RESULTS

Using the real-time PCR method, it was possible to detect the presence of all bacterial species tested with an initial concentration of 10 CFU mL^-1 24 h after contamination, except for Staphylococcus hominis. The PCR assay also detected, at 24 h, the presence of Serratia marcescens and Enterobacter cloacae with an initial concentration of 1 CFU mL^-1 .

CONCLUSIONS

The real-time PCR assay may be a reliable alternative to conventional culture methods in the screening of bacterial contamination of PCs, enabling bacterial detection even with a low initial concentration of microorganisms.

Bacillus cereus septicemia attributed to a matched unrelated bone marrow transplant

BACKGROUND

Hematopoietic cell transplantation (HCT) is performed in more than 25,000 patients annually. Clinically significant bacterial transmission from HCT products is rare.

CASE REPORT

A 36-year-old male of Asian descent with chronic myelogenous leukemia developed sepsis leading to acute renal failure and disseminated intravascular coagulation during infusion of matched unrelated donor bone marrow. This product later tested positive for Bacillus cereus.

DISCUSSION

This HCT product traveled 31 hours at room temperature before arriving at the transplant center. Reducing transport times, transporting at 4 °C, and enhancing bacterial surveillance of HCT products may increase the ability to detect bacterial proliferation from transport.

CONCLUSION

To prevent a similar case in the future, we will begin Gram staining all HCT products in transit more than 24 hours to alert physicians of the need for prophylactic antibiotic therapy.

In vitro effects on platelets irradiated with short-wave ultraviolet light without any additional photoactive reagent using the THERAFLEX UV-Platelets method

BACKGROUND

A novel short-wave ultraviolet light (UVC) pathogen reduction technology (THERAFLEX UV-Platelets; MacoPharma, Mouvaux, France) without the need of any additional photoactive reagent has recently been evaluated for various bacteria and virus infectivity assays. The use of UVC alone has on the one hand been shown to reduce pathogens but may, on the other hand, have some impact on the platelet (PLT) quality. The purpose of this study was to determine the potential effects on PLT quality of pathogen inactivation treatment using the novel UVC method for PLT concentrates.

STUDY DESIGN AND METHODS

Buffy-coat-derived PLTs suspended in SSP+ were irradiated with UVC light in plastic bags (MacoPharma) made of ethyl vinyl acetate, considered to be highly permeable to UVC light. The UVC-treated (test, n=8) as well as the untreated (reference, n=8) PLT units were stored in PLT storage bags composed of n-butyryl, tri n-hexyl citrate-plasticized polyvinyl chloride (MacoPharma) on a flat bed agitator for in vitro testing during 7 days of storage.

RESULTS

No significant difference in PLT counts and lactate dehydrogenase between the groups was detected. During storage, glucose decreased more and lactate increased more in the test units. Statistically significant differences were found for glucose (P<0·01) and lactate (P<0·05) on day 7. ATP levels were higher (P<0·01 from day 5) in the reference units. With exception of day 7 (P<0·01 reference vs. test), hypotonic shock response reactivity was not different between groups. Extent of shape change was lower (P<0·01), and CD62P (P<0·05 day 5) was higher in the test units. CD42b and CD41/61 showed similar trends throughout storage, without any significant difference between the units. pH was maintained at >6·8 (day 7) and swirling remained at the highest level (score = 2) for all units throughout storage.

CONCLUSION

Our results suggest that irradiation with UVC light has a slight impact on PLT in vitro quality and appears to be insignificant with regard to current in vitro standards.

Bacterial contamination of platelets

Bacterial contamination of platelet products, both single donor apheresis platelet units and whole blood-derived platelet pools, continues to occur despite preventive measures. While some advances have been made in decreasing the rate of bacterial contamination of platelet units, particularly through diversion methods and early culture, a great deal remains to be done to eliminate the problem. Diversion methods have decreased contamination rates associated with skin commensal organisms. Culture methods are now widely used and many at-issue detection methods have been developed or are undergoing development. This article reviews the current developments and the challenges that remain to minimize and detect bacterial contamination of platelet products.

Analysis of bacterial detection in whole blood-derived platelets by quantitative glucose testing at a university medical center

After the March 2004 implementation of American Association of Blood Banks standards regarding platelet bacterial detection, we began quantitative glucose screening of whole blood-derived platelets (WB-P). The glucose level was measured immediately before component release--often storage day 4 or 5--using the Glucometer SureStep Flexx Meter (LifeScan, Milpitas, CA), with a positive cutoff of less than 500 mg/dL; failing units were cultured and not transfused. During 29 months (March 1, 2004-July 31, 2006) 93,073 units of WB-P were tested. Initially, 929 units (0.998%) screened positively. Bacterial growth was culture-confirmed in 6 units, for a bacterial contamination incidence of 0.006% and a true-positive rate of 6.4/100,000. Three additional culture-confirmed contamination cases were detected in transfused units causing febrile nonhemolytic reactions, for a false-negative rate of 3.2/100,000. Our overall contamination prevalence was 9.6/100,000 units of platelets transfused, lower than ordinarily cited, and showed a false-negative rate remarkably congruent to that of culture: 3.2/100,000. A low-sensitivity screening test applied late in platelet shelf-life can be comparable to culture in preventing bacterial-related morbidity.

Methods for the detection of bacterial contamination in blood products

Culture-based and molecular assays have been developed for the screening of platelet concentrates and other blood components for bacterial contaminations. In this review, the principles of the assays are outlined. The focus of this review is the assessment of the analytical qualities of the methods. Spiking studies by adding defined levels of a wide range of bacteria to the complex biological matrix provide the first basis to evaluate and compare the qualities of methods for bacterial detection. The sensitivity acceptable for reliable screening for bacteria critically depends on the timing of either early sampling (within a period of up to 24 h after preparation of the blood component) or late sampling (a few hours before issuing the blood component). Large screening studies are essential to confirm both adequate sensitivity and specificity of the testing. In the ideal setting, these studies are prospectively planned and include systematic surveillance of adverse events in response to the administration of the screened products. The findings from sterility testing (predominantly with automated systems for detection of bacteria based on CO(2) generation) of more than 550,000 platelet concentrates in 13 studies are summarised. The limitations of the early sampling and the "negative-to-date" strategy to issue platelet concentrates are addressed. A few reported cases of probable transmission of bacteria by platelet transfusion despite negative screening tests emphasise the need to further develop optimised methods for testing of bacteria blood components.

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.

Platelet transfusions

Ever since platelet transfusions were shown to reduce mortality from haemorrhage in patients with acute leukaemia in the 1950s, the use of this therapy has steadily grown to become an essential part of the treatment of cancer, haematological malignancies, marrow failure, and haematopoietic stem cell transplantation. Today, more than 1.5 million platelet products are transfused in the USA each year, 2.9 million products in Europe. However, platelet transfusion can transmit infections and trigger serious immune reactions and they can be rendered ineffective by alloimmunisation. There are several types of platelet components and all can be modified to reduce the chances of many of the complications of platelet transfusion. Transfusion practices, including indications for transfusion, dose of platelets transfused, and methods of treating alloimmunised recipients vary between countries, and even within countries. We review commonly used platelet components, product modifications, transfusion practices, and adverse consequences of platelet transfusions.

[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.

Bacterial risk reduction by improved donor arm disinfection, diversion and bacterial screening

The Interventions of improved donor arm disinfection, diversion and bacterial screening have been implemented by blood services and shown to have substantial benefit. The major source of bacterial contamination is donor arm derived. Blood services are now introducing best practice donor arm disinfection techniques. Diversion has been shown to substantially reduce bacterial contamination in the order of 40-88%. Diversion, together with improved donor arm disinfection, has shown to improve the percentage of reduction in contamination from 47% to 77%. Residual contamination levels after the Introduction of diversion and improved donor arm disinfection may be in the order of 30-40%. Numerous countries have now implemented screen testing programmes for platelet concentrates, which are the major source of bacterial transfusion transmission. Pathogen reduction systems have been developed and are under development. At present, concerns remain with these systems regarding cost, process control, ability to inactivate high titres of viruses, killing of bacterial spores, product damage, genotoxicity and mutagenicity. The interventions of diversion, improved donor arm disinfection and bacterial screen testing are currently available, As such they can be implemented now to increase blood safety with no associated patient risk.

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

BACKGROUND

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

STUDY DESIGN AND METHODS

PBC was studied by prospective (active) and transfusion-reaction triggered (passive) surveillance from July 1991 to December 2004. Active surveillance, utilized for 10 years, included bacterial culture of all or 4- and 5-day-old PLTs at issue and intermittent use of Gram stain, pH measurements, and early (24-hr) culture of single-donor plateletpheresis (SDP) units.

RESULTS

Active surveillance detected 38 instances of PBC, 7 in SDP units (1:2213) and 31 in random-donor PLT units (1:2090 units, p = 0.89; or 1:418 pools of 5 units, p < 0.001). Contaminants were coagulase-negative staphylococci (CONS; n = 27), Staphylococcus aureus (4), Bacillus cereus (1), Serratia marcescens (2), streptococci (2 S. bovis, 1 S. uberis), and CONS with viridans group streptococcus (1). Only one instance of contamination, caused by Pseudomonas aeruginosa, was detected by passive surveillance, with fatal outcome. Colony counts of contaminants ranged from 0.5 x 10(2) to 4 x 10(11) colony-forming units per mL at time of issue. PBC was interdicted before transfusion in 6 cases through Gram stain screening. Transfusion reactions occurred in 13 of 32 recipients (41%), with 9 severe reactions (28%) and 3 deaths (9%). pH testing failed to detect 5 contaminated units and resulted in discard of nearly 2 percent of units, whereas culture of SDP units at 24 hours failed to identify a contaminated unit.

CONCLUSION

Improved active surveillance methods for detecting PBC are needed to improve the safety of PLT transfusions.

Sterility testing of platelet concentrates prepared from deliberately infected blood donations

BACKGROUND

In general the bacterial count in freshly donated blood is low and even lower in the corresponding platelet concentrates (PCs). By use of flow cytometry (FACS) for sterility testing, the reliability of early versus later sampling times was evaluated.

STUDY DESIGN AND METHODS

Blood donations were spiked with various numbers of Staphylococcus epidermidis, Staphylococcus aureus, Bacillus cereus, and Klebsiella pneumoniae. The corresponding PCs were prepared by the buffy-coat method and stored at 22 degrees C. A 20-mL sample was collected from each PC directly after preparation and after 8 hours. Samples were stored at 35 degrees C. Sterility testing of both PCs and samples was by FACS analysis at different time points.

RESULTS

All stored PCs were found positive by FACS analysis, with detection times ranging between 8 and 24 hours (K. pneumoniae, B. cereus), 8 and 91 hours (S. aureus), and 144 hours (S. epidermidis). In the samples incubated at 35 degrees C, bacteria were detected after 8 to 19 hours (K. pneumoniae, B. cereus), 8 to 67 hours (S. aureus), and 19 to 43 hours (S. epidermidis). Some of the samples did not contain bacteria.

CONCLUSION

Detection times for slow-growing bacteria are significantly shortened when PC samples are incubated at 35 degrees C: the numbers of bacteria in freshly prepared PCs may, however, be so low that the samples drawn for sterility testing do not contain a single bacterium. Our results do not support a shortening of the 24-hour or greater sampling time recommended by the manufacturers of established test systems, because also for consistent detection by FACS, bacteria need to grow in the PCs to sufficient numbers.

Evaluation of the enhanced bacterial detection system for screening of contaminated platelets

BACKGROUND

The Pall third-generation enhanced bacterial detection system (eBDS) was recently approved for detection of bacterial contamination in leukoreduced platelets (PLTs). The method is based on the measurement of the oxygen content as a marker for bacteria. eBDS incorporates major modifications including removal of the sample-set filter, modification of the culture medium, and incubation with agitation of the sample pouch.

STUDY DESIGN AND METHODS

Ten whole blood-derived random-donor PLT units collected on Day 1 after donation and 10 single-donor apheresis PLT units were spiked with low levels of bacteria in three different blood transfusion centers. Inoculation was performed at a final concentration of 5 to 50 colony-forming units per mL with reference strains of five organisms involved in severe transfusion-associated infections. PLT units were stored at 22 degrees C for 24 hours before sampling. Six sample sets were then sterile-connected to each unit and placed on a horizontal agitator at 35 degrees C for 18 or 24 hours of incubation.

RESULTS

No false-positive results were obtained, indicating a 100 percent specificity of the assay. Of 126 spiked sample pouches tested, 61 of 63 (96.82%) and 63 of 63 (100%) were detected positive after 18 or 24 hours of incubation, respectively. In the two missed cases that failed to detect Bacillus cereus, the measured oxygen was slightly above the detection threshold but was markedly different from the negative samples.

CONCLUSION

The eBDS method allows definitive testing of PLTs as soon as 42 hours after collection and offers an alternative culture method to the BacT/ALERT system.

Basics of flow cytometry?based sterility testing of platelet concentrates

BACKGROUND

Flow cytometry (FACS) is a common technique in blood banking. It is used, for example, for the enumeration of residual white blood cells in plasma and in cellular blood products. It was investigated whether it can also be applied for sterility testing of buffy coat-derived platelet concentrates (PCs).

STUDY DESIGN AND METHODS

Plasma-reduced PCs were spiked with bacteria and stored at 20 to 24 or 37 degrees C for various times. The following 10 species were used: Bacillus cereus, Enterobacter cloacae, Escherichia coli, Klebsiella pneumoniae, Propionibacterium acnes, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis, Serratia marcescens, and Yersinia enterocolitica. Bacterial DNA was stained with thiazole orange. After the platelets were lysed, bacteria were enumerated by FACS.

RESULTS

All bacteria species used were detectable by FACS. The lower detection limit was approximately 100 bacteria per microL, that is, 10(5) per mL. In general, the titers measured were 1.2- to 3-fold higher than those determined by colony forming assay. In one case (K. pneumoniae) in which the dot plot of the bacteria cloud overlapped with that of bacteria debris, they were consistently lower. When PC samples were inoculated with approximately 1 colony-forming unit per mL of bacteria and kept at 37 degrees C, most species were detected within 21 hours or less. Exceptions were E. cloacae and P. acnes, which were detected after 24 to 40 and 64 hours, respectively. At 20 to 24 degrees C, the detection times were strongly prolonged.

CONCLUSION

Sterility testing of PCs by FACS is a feasible approach. The present data suggest incubating PC samples for 20 to 24 hours at 37 degrees C before testing. For slow-growing bacteria, the incubation period must be prolonged by 1 to 2 days.

Pall eBDS: an enhanced bacterial detection system for screening platelet concentrates

Bacterial contamination of blood components remains a significant problem in transfusion medicine. The Pall enhanced bacterial detection system (Pall eBDS) detects the presence of bacteria in leucodepleted platelet concentrates by measuring the reduction of oxygen in the sample, due to aerobic bacterial growth. Pooled platelet concentrates were spiked at 10 cfu mL(-1) with 10 organisms (one species per bag). Pall eBDS pouches were inoculated with the spiked platelet concentrates. After 24 and 30 h of incubation, the oxygen level was measured. A further set of pouches were taken from the inoculated platelet concentrates at 24 h. Incubation and reading intervals were as for the initial set of pouches. A sensitivity study was also performed comparing the Pall eBDS with the BacT/ALERT system. Spiking at 10 cfu mL(-1) and immediately sampling into Pall eBDS pouches resulted in 97.6 and 100% detection after an incubation period of 24 and 30 h, respectively. After 24 h of incubation of the spiked platelet concentrates and then sampling into Pall eBDS pouches, 99.1% detection was obtained after incubation for both 24 and 30 h. The sensitivity of the Pall eBDS and BacT/ALERT is similar and in the order of 1 cfu mL(-1). Implementation of either BacT/ALERT or Pall eBDS for routine screening of platelet concentrates has the potential to further increase the safety of the blood supply.

Evaluation of pooled cultures for bacterial detection in whole blood-derived platelets

BACKGROUND

The BacT/ALERT (bioMérieux) system is highly efficient for bacterial detection in apheresis platelets (PLTs) and whole blood-derived PLTs produced by the buffy-coat method. Detection of bacterial contamination in whole blood-derived PLTs produced by the PLT-rich plasma (PRP) method, however, is problematic. Prestorage pooling of these PLTs is not permitted in some countries including Canada and the United States, and culturing individual units is costly and may significantly reduce the PLT unit content. In this study, the sensitivity and specificity of BacT/ALERT cultures performed on pools derived from PRP PLTs are reported.

STUDY DESIGN AND METHODS

The sensitivity of the BacT/ALERT system was evaluated for bacterial detection in PRP PLTs with a dilution effect. Thirty PLT pools were produced with 1 PLT unit previously spiked with bacteria and then pooled with other four nonspiked PLT units. Three bacteria, usually associated with PLT contamination, were selected for spiking. The specificity of this method was evaluated in 40 nonspiked PLT pools.

RESULTS

The method was found to be 100 percent specific and 97 percent sensitive. Of the five spiked pools with Streptococcus pneumoniae at levels of less than 2 colony-forming units (CFUs) per mL, four were found to be positive whereas all 25 spiked pools with greater than 9 CFUs per mL of any of the chosen bacteria gave positive results. The mean time of detection was 17 to 19 hours for Staphylococcus epidermidis and 14 to 15 hours for S. pneumoniae and Pseudomonas aeruginosa when spiked with similar bacterial inocula.

CONCLUSION

The evaluated system is highly sensitive and specific and may be a feasible method for bacterial detection in PRP PLTs.

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.

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.

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

BACKGROUND

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

STUDY DESIGN AND METHODS

Leukoreduced whole blood-derived PLT concentrates (LR-PCs) and LR single-donor PLTs (LR-SDPs) were inoculated with 1 to 15 colony-forming units (CFUs) of bacteria per mL in studies of each of 10 bacterial species associated with fatal transfusion-transmitted bacterial infection. Immediately after inoculation and after 24 hours of storage at 22 degrees C, samples of inoculated LR-PCs were aseptically transferred into the eBDS pouches. Pouches were then incubated for 24 hours at 35 degrees C with agitation and oxygen concentration was then measured.

RESULTS

Median inoculation levels ranged from 5 to 13 CFUs per mL for each species studied. No significant differences in oxygen concentration were found when comparing LR-PCs with LR-SDPs. When sampling occurred from the PLTs 24 hours after inoculation, all 280 cases (24-33 replicates of each species) were detected as contaminated by the device (100% sensitivity). No false-positives were obtained with 713 uninoculated PLT units.

CONCLUSIONS

The eBDS demonstrated improved detection sensitivity in the range of 1 to 15 CFUs per mL with no observed false-positives compared to the original BDS (detection range 100 to 500 CFUs/mL) with no false-positives.

Detection of bacteria in platelet concentrates: comparison of broad-range real-time 16S rDNA polymerase chain reaction and automated culturing

BACKGROUND

Based on real-time polymerase chain reaction (PCR) technology, a broad-range 16S rDNA assay was validated and its performance was compared to that of an automated culture system to determine its usefulness for rapid routine screening of platelet concentrates (PCs).

STUDY DESIGN AND METHODS

The presence of bacteria in pooled PCs was routinely assessed in an automated culturing system (BacT/ALERT, bioMerieux). The PCR assay was performed with DNA extracted from the same samples as used for culturing. DNA extraction was performed with a automated extraction system (MagNA Pure, Roche Diagnostics). PCR amplification was performed with a set of universal primers and probe targeting eubacterial 16S rDNA.

RESULTS

A total of 2146 PCs were tested. Eighteen (0.83%) samples were found to be contaminated. These samples were positive for the presence of bacteria by both methods. All contaminants were identified as bacteria belonging to the common human skin flora. These included Propionibacterium spp. (n = 7), Staphylococcus spp. (n = 6), Bacillus spp. (n = 2), Micrococcus spp. (n = 2), and Peptostreptococcus spp. (n = 1). Estimation of the bacterial load in PCs by real-time PCR showed that the initial levels of contamination varied between 13.6 and 9 x 10(4) colony-forming unit equivalents per PCR procedure.

CONCLUSIONS

Compared to culture in the BacT/ALERT system, the PCR assay had a sensitivity of 100 percent and a specificity of 100 percent. This real-time PCR assay has a much shorter turnaround time of 4 hours, which offers the possibility to test and obtain results on PCs before release or the day they are transfused. This would permit the withdrawal of contaminated PCs before transfusion.