Evaluation of swirling, pH, and glucose tests for the detection of bacterial contamination in platelet concentrates

Platelet components and bacterial contamination: hospital perspective 2022

Bacterial contamination of platelet units has been one of the most common transfusion-transmitted infections. Approximately 4 to 7 fatalities are being reported to the US Food and Drug Administration (FDA) annually, which cites bacterially contaminated platelet units as the cause. Over the past 3 decades, different mitigation strategies have been introduced to minimize the risk of morbidity and mortality related to contaminated platelet units. The process of platelet collection and manufacturing as well as storage at 20°C to 24°C contributes to higher prevalence of contaminated units. The risk of transfusing bacterially contaminated platelets can be lowered using different types of interventions. Prevention of bacterial contamination can be done by strict adherence to techniques that minimize contamination during unit collection. The detection of bacteria in platelet products can be improved with a combination of rapid testing and bacterial cultures that involve large volume and delayed sampling. Finally, pathogen reduction can inactivate bacteria or other pathogens present in the unit. This article describes different strategies that blood centers and transfusion services have undertaken since October 2021 to meet FDA guidance requirements. Market forces as well as feasibility of different FDA-proposed approaches have limited the number of practical solutions to just a few. In addition, the blood product availability required hospitals to adopt more progressive strategies to provide patients with needed platelet products.

Quality validation of platelets obtained from the Haemonetics and Trima Accel automated blood-collection systems

BACKGROUND

Platelet transfusion is required to treat haemo-oncology or trauma patients. Platelet apheresis (PA) performed with apheresis equipment has increased rapidly in recent years. Leucocyte-reduced platelet apheresis (LRPA) can reduce the risk of platelet refractoriness and febrile nonhemolytic transfusion reactions (FNHTRs) for transfusion. Accordingly, this study aimed to investigate and compare the platelet metabolic and functional responses between PA performed with Haemonetics and LRPA performed with Trima Accel cell separator.

METHODS

The qualities of platelets collected through PA and LRPA were evaluated in terms of visual appearance, morphology, platelet-aggregation changes, metabolic activities, and bacterium-screening test during 5-day storage. Statistical analyses included two-sample t-test and generalised estimating equation(GEE) method.

RESULTS

During 5-day storage in LRPA, residual leucocytes were all <1.0×10⁶, and the parameters of platelet function were as follows: platelet aggregated to agonists such as adenosine 5'-diphosphate (ADP) and collagen, and the extent of shape change and pO₂ showed no statistically significant difference between PA and LRPA. The hypotonic shock reaction (HSR) on days 0, 1, and 3 were significantly higher in LRPA than in PA (71.78±6.92 vs. 64.10±7.42; P=0.002; 71.53±8.98 vs. 62.96±9.84; P=0.007; 68.05±7.28 vs. 57.76±6.80; P<0.0001, respectively). Values of mean platelet volume (MPV) were statistically larger in PA than in LRPA on days 0, 1, and 3. On day 5, the swirling score was higher in LRPA than in PA. The mean lactate levels had no statistically significant difference between PA and LRPA. Moreover, no growth was observed through bacterium-screening test conducted on 40 samples.

CONCLUSION

Comparison of LRPA and PA products collected from the Trima Accel and Haemonetics automated blood-collection systems, respectively, revealed that both products possessed good platelet qualities even though additional processes are needed to reduce leucocytes. Furthermore, investigating the outcomes of other apheresis instruments with focus on the safety of donors, products, and recipients is necessary.

Evaluation of bacterial inactivation in random donor platelets and single-donor apheresis platelets by the INTERCEPT blood system

BACKGROUND:

Blood transfusion of contaminated components is a potential source of sepsis by a wide range of known and unknown pathogens. Collection mechanism and storage conditions of platelets make them vulnerable for bacterial contamination. Several interventions aim to reduce the transfusion of contaminated platelet units; however, data suggest that contaminated platelet transfusion remains very common.

AIM:

A pathogen inactivation system, “INTERCEPT”, to inactivate bacteria in deliberately contaminated platelet units was implemented and evaluated.

MATERIALS AND METHODS:

Five single-donor platelets (SDP) and five random donor platelets (RDP) were prepared after prior consent of donors. Both SDP and RDP units were deliberately contaminated by stable stock ATCC Staphylococcus aureus and Escherichia coli, respectively, with a known concentration of stock culture. Control samples were taken from the infected units and bacterial concentrations were quantified. The units were treated for pathogen inactivation with the INTERCEPT (Cerus Corporation, Concord, CA) Blood system for platelets (Amotosalen/UVA), as per the manufacturer's instructions for use. Post illumination, test samples were analyzed for any bacterial growth.

RESULTS:

Post-illumination test samples did not result in any bacterial growth. A complete reduction of >6 log₁₀S. aureus in SDP units and >6 log₁₀Escherichia coli in RDP units was achieved.

CONCLUSION:

The INTERCEPT system has been shown to be very effective in our study for bacterial inactivation. Implementation of INTERCEPT may be used as a mitigation against any potential bacterial contamination in platelet components.

Diagnostic methods for platelet bacteria screening: current status and developments

Bacterial contamination of blood components and the prevention of transfusion-associated bacterial infection still remains a major challenge in transfusion medicine. Over the past few decades, a significant reduction in the transmission of viral infections has been achieved due to the introduction of mandatory virus screening. Platelet concentrates (PCs) represent one of the highest risks for bacterial infection. This is due to the required storage conditions for PCs in gas-permeable containers at room temperature with constant agitation, which support bacterial proliferation from low contamination levels to high titers. In contrast to virus screening, since 1997 in Germany bacterial testing of PCs is only performed as a routine quality control or, since 2008, to prolong the shelf life to 5 days. In general, bacterial screening of PCs by cultivation methods is implemented by the various blood services. Although these culturing systems will remain the gold standard, the significance of rapid methods for screening for bacterial contamination has increased over the last few years. These new methods provide powerful tools for increasing the bacterial safety of blood components. This article summarizes the course of policies and provisions introduced to increase bacterial safety of blood components in Germany. Furthermore, we give an overview of the different diagnostic methods for bacterial screening of PCs and their current applicability in routine screening processes.

[Control of the bacterial risk of transfusion in France in 2013]

Bacterial contamination of blood products (BP) remains the most important infectious risks of blood transfusion in 2013. Platelet concentrates (PC) are the blood products the most at risk, whether CPA or MCPS. In France, the residual risk has been steadily declining since 1994. For the platelets, the frequency of transfusion reaction due to bacterial contamination (TRBC) is now about at one per 50,000 CP distributed. The number of deaths has remained stable since 1994 with one death per year (300,000 distributed CP). The progressive decrease in the number of cases of TRBCs is the result of steady improvement of practices and prevention methods at all stages from collection to the transfusion of BP. But if all these improvements have significantly reduced the incidence of TRBCs, mortality is not changed with the CP and the reduction of this risk is a priority for the French Blood Establishment (EFS). Detection methods of CP contaminated or pathogen inactivation are two approaches available and can provide a significant reduction (for the former) or deletion (for seconds) of the risk of transfused contaminated CP. Currently, the choice is in favor of the detection of bacteria. New detection "rapid tests" methods were added to the panel of candidates and are being evaluated. Inactivation of pathogens remains the safest prospect of eliminating this adverse effect of transfusion. Implementation of one method for bacterial detection is probably a transitional measure.

Comparison of cytokine levels and metabolic parameters of stored platelet concentrates of the Fundação Hemominas, Belo Horizonte, Brazil

Background

Prolonged storage of platelets could improve availability and logistical management and decrease wastage. Immunobiochemical methods can be used to guarantee the quality of platelets after prolonged storage.

Objective

The aim of this study was to compare storage-related changes in buffy coat-derived platelet concentrations versus platelet-rich plasmal.

Methods

Units of whole blood were drawn using a quadruple-bag blood container system. Platelet-rich plasma and buffy coat prepared from whole blood following standard methods were stored for 9 days. During this period test samples were aseptically collected for analysis on Days 1, 2, 3, 5, 7 and 9.

Results

The highest CD42b expression was greater than 95%. The percentage of CD62p was significantly lower than the CD42b expression. The pH remained fairly stable during storage. Measurement of pO₂ and pCO₂ showed that oxygen levels were significantly higher than carbon dioxide levels. There were no significant differences in bicarbonate levels, glucose consumption and lactate production between the groups. The swirling effect with platelet-rich plasma samples decreased after 5 days of storage and after 7 days of storage for buffy coat samples. There was a significant twenty-fold increase in the mean IL-1β after 5 days of storage for both groups. Slight increases in IL-6 and IL-8 levels were seen at 5 days.

Conclusion

The quality of platelet concentrates remained acceptable during 7 days of storage in respect to the swirling effect, pH and platelet activation. There were no significant differences between buffy coat-derived platelets and platelet-rich plasma in this study.

Effect of platelet additive solution on bacterial dynamics and their influence on platelet quality in stored platelet concentrates

BACKGROUND

Platelet additive solutions (PASs) are an alternative to plasma for the storage of platelet concentrates (PCs). However, little is known about the effect of PAS on the growth dynamics of contaminant bacteria. Conversely, there have been no studies on the influence of bacteria on platelet (PLT) quality indicators when suspended in PAS.

STUDY DESIGN AND METHODS

Eight buffy coats were pooled, split, and processed into PCs suspended in either plasma or PAS (SSP+, MacoPharma). PCs were inoculated with 10 and 100 colony-forming units (CFUs)/bag of either Serratia liquefaciens or Staphylococcus epidermidis. Bacterial growth was measured over 5 days by colony counts and bacterial biofilm formation was assayed by scanning electron microscopy and crystal violet staining. Concurrently, PLT markers were measured by an assay panel and flow cytometry.

RESULTS

S. liquefaciens exhibited an apparent slower doubling time in plasma-suspended PCs (plasma-PCs). Biofilm formation by S. liquefaciens and S. epidermidis was significantly greater in PCs stored in plasma than in PAS. Although S. liquefaciens altered several PLT quality markers by Days 3 to 4 postinoculation in both PAS- and plasma-PCs, S. epidermidis contamination did not produce measurable PLT changes.

CONCLUSIONS

S. liquefaciens can be detected more quickly in PAS-suspended PCs (PAS-PCs) than in plasma-PCs by colony counting. Furthermore, reduced biofilm formation by S. liquefaciens and S. epidermidis during storage in PAS-PCs increases bacteria availability for sampling detection. Culture-based detection remains the earliest indicator of bacterial presence in PAS-PCs, while changes of PLT quality can herald S. liquefaciens contamination when in excess of 10(8) CFUs/mL.

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.

Direct detection of the bacterial stress response in intact samples of platelets by differential impedance

BACKGROUND

We have previously described a new rapid approach that relies on monitoring intentionally stressed bacteria in contaminated platelet concentrates (PCs). This earlier work included human cell lysis with Triton X-100 and filtration as steps in the sample preparation. This study was undertaken to develop an improved and time-saving protocol that enables direct bacterial detection in PCs without lysis and filtration.

STUDY DESIGN AND METHODS

Apheresis- or whole blood-derived PCs were spiked with 17 model bacteria and tested at final concentrations from 10(3) to 10(6) colony-forming units (CFUs)/mL. The contaminated PCs were treated with a chemical compound that induces a stress response in bacteria and monitored using differential impedance sensing to detect and record subtle changes in the dielectric permittivities of the contaminated platelet (PLT) samples.

RESULTS

No measurable responses from sterile PLT samples were observed during exposure to the compounds used as stressors. In contrast, distinct response profiles were obtained without exception for all 17 bacterial species for all bacterial concentrations tested. Bacterial presence was established within 5 to 10 minutes for high inocula (10(6) and 10(5) CFUs/mL) while low inocula (10(4) and 10(3) CFUs/mL) were usually detectable within 20 minutes. The entire testing process routinely took less than 30 minutes from the point of sampling to the time that the final results are available.

CONCLUSIONS

The results described here demonstrate that monitoring the development of stress in bacteria is a fast and simple way to detect 10(3) CFUs/mL or more bacteria in complex cellular blood products such as PCs.

Use of the RQI test for bacterial screening of whole blood platelets

We compare our experience using a new rapid qualitative immunoassay (RQI) test (platelet Pan Genera Detection, Verax, Worcester, MA) for bacterial screening of whole blood platelet (WBP) pools with our previous WBP bacterial screen, pH testing. All WBP pools were RQI tested at the time of issue. All RQI+ pools were cultured in an automated culture system, with subsequent bacterial identification if the culture was positive. During approximately 5.5 months, 7,733 WBP pools were RQI tested. There were 14 positive RQI tests; 12 WBP pools were sterile when cultured and considered false-positive RQI tests. One pool was positive for coagulase-negative Staphylococcus, while another was positive for group B Streptococcus. The specificity and positive predictive value of the RQI test were 99.85% and 14.3%, respectively. The specificity and positive predictive value of the RQI test were higher than pH testing, leading to less waste of sterile WBP pools.

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.

Evaluation of in vitro storage properties of prestorage pooled whole blood-derived platelets suspended in 100 percent plasma and treated with amotosalen and long-wavelength ultraviolet light

BACKGROUND

Amotosalen, a psoralen, has been utilized for photochemical treatment (PCT) of apheresis platelets (PLTs) and pooled buffy coat PLTs suspended in additive solution. In the United States, the source of many PLT transfusions is from whole blood-derived PLTs prepared by the PLT-rich plasma (PRP) method. This study investigated the in vitro PLT properties of amotosalen-PCT of leukoreduced pools of PLTs prepared by the PRP method and suspended in 100 percent plasma.

STUDY DESIGN AND METHODS

On Day 1 of storage, 12 leukoreduced (n = 6) or 10 leukoreplete (n = 6) ABO-identical PLT concentrates were pooled, separated into two pools of 6 or 5 units, respectively, and leukoreduced (leukoreplete pools only). Each pool of 5 or 6 units was then photochemically treated (designated "test": amotosalen plus 3.0 J/cm(2) long-wavelength ultraviolet light followed by amotosalen/photoproduct removal) while the remaining identical pool (designated "control") was untreated. PLT in vitro assays were performed on test and control pools during 7-day storage.

RESULTS

PCT resulted in slightly reduced pH in test pools compared to that of matched control pools after 5 days of storage (5-unit pools: test, 6.96 +/- 0.12 vs. control, 7.15 +/- 0.09, p = 0.0033; 6-unit pools: test, 6.90 +/- 0.10 vs. control, 7.07 +/- 0.09, p < 0.0001). Test pools adequately maintained many other in vitro properties including PLT morphology, hypotonic shock response, and extent of shape change parameters during 5-day storage, which, like pH, also differed from those of controls. The pH of test and control pools declined on Day 7, with 1 of 6 test pools (either 5 or 6 units) having a pH value of less than 6.20, while all control pools had pH values of more than 6.66.

CONCLUSION

PCT of leukoreduced PLT pools of whole blood-derived PLTs in 100 percent plasma maintained adequate PLT in vitro variables through 5 days of storage.

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.

Screening platelet concentrates for bacterial contamination: low numbers of bacteria and slow growth in contaminated units mandate an alternative approach to product safety

BACKGROUND AND OBJECTIVES

We introduced 100% screening of platelets for bacterial contamination in 2005 to reduce the risk of clinical sepsis from platelet transfusion. We test all outdating units again at expiry to assess the sensitivity of the initial test.

MATERIALS AND METHODS

We test all platelet concentrates prior to release for clinical use using a large volume automated culture technique on the day after manufacture. All units that expire unused are retested. Platelets still in stock on day 4 of storage may have a repeat culture performed, and are returned to stock with two extra days of shelf life.

RESULTS

Of 43,230 platelet units screened, 35 (0.08%) were positive; of 8282 expired unused, 18 (0.22%) were positive; and of 3310 day-4 retests, four (0.12%) were positive. Overall sensitivity of the initial screening test was 29.2% (95% confidence interval 19.4 to 39.1%). Thirteen of the 35 positive screening tests would have been expected to grow in both aerobic and anaerobic bottles; eight grew in aerobic culture only and five grew in anaerobic culture only, indicating that the likely number of bacteria in the contaminated platelet units at the time of sampling was less than 60 colony-forming unit per platelet unit.

CONCLUSIONS

Screening platelet concentrates for bacterial contamination using the most sensitive method available has a sensitivity of less than 40% because of the low numbers of bacteria in the initial contamination. Effective resolution of this problem will require a pathogen-inactivation technique.

Strategies of bacteria screening in cellular blood components

Since the impressive reduction of transfusion-transmitted virus infections, bacterial infections by blood transfusion represent the most important infection risk. Platelet concentrates are the current focus of attention, as they are stored under temperature conditions which allow growth of contaminating bacteria up to 10(10) and more microbes per platelet bag. This paper does not consider the pathogen reduction methods but will assess suitable screening methods. Beside conventional microbiological approaches or surrogate markers, several efficient methods able to detect bacterial contamination in platelets are available on the market. They need to be divided into two different methodological principles: the cultivation methods and rapid methods. Cultivation or incubation methods require some time for signal production as they depend on growth of microbes. Thus, they have to be combined with early sampling, i.e., the sample to be examined has to be drawn from the blood component 1 day after donation. Their advantage is the relatively uncomplicated implementation into the logistics of blood banks. Because of the initially very low count of bacteria after donation, a certain small sampling error in application of that strategy remains. Rapid methods are able to produce the diagnosis within a short time. Therefore, they allow postponing of sample drawing, ideally up to the time immediately before transfusion. However, this procedure causes logistic complications. On the other hand, late sampling combined with a rapid method will prevent the transfusion of highly contaminated platelet concentrates leading to acute septic shock up to the death of the patient. Considering the sum of different aspects including the supply of patients, the potential improvement of microbial safety of platelet concentrates is comparable in both strategies.

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.

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

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

[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.

Use of a pH meter for bacterial screening of whole blood platelets

BACKGROUND

Bacterial contamination of blood products is a leading cause of transfusion-related morbidity and mortality. Transfusion services are now compelled to employ methods of detecting bacteria in platelet (PLT) components. The use of pH screening of whole-blood PLTs (WBPs) was evaluated with a pH meter at the time of issue as a surrogate test for bacterial contamination.

STUDY DESIGN AND METHODS

All WBPs selected for transfusion in May through September 2004 were tested individually for pH at time of issue. Those with a pH value of less than 7.0 were cultured in an automated culture system for 5 days. The white blood cell (WBC) and PLT counts in 56 representative WBP units that failed pH screening were compared to WBP units with acceptable pH values.

RESULTS

Of the 37,060 WBP units that underwent pH screening, 405 had a pH value of less than 7.0 (1.1%). Four of those units were culture positive (1.0%) for Staphylococcus aureus, Bacillus subtilis, diphtheroids, and coagulase-negative Staphylococcus. Only one cocomponent red blood cell (RBC) unit was culture-positive and grew the same bacteria (S. aureus) as the WBP unit. The rate of pH failure increased with WBP storage length with the greatest rate of pH failures occurring in 5-day-old WBPs. The units that failed pH screening had significantly more WBCs and PLTs than units with acceptable pH values.

CONCLUSION

pH screening of WBPs at issue prevented transfusion of bacterially contaminated WBPs and RBCs. This method, however, results in significant PLT wastage. Higher WBC and PLT content likely explains pH failures not due to bacterial contamination.

In-house validation of the BACTEC 9240 blood culture system for detection of bacterial contamination in platelet concentrates

BACKGROUND

At present, only two commercially available automated culture systems are cleared by the FDA for the purpose of quality control (QC) testing for bacterial contamination of platelet (PLT) concentrates: the BacT/ALERT blood culture system (bioMérieux) and the Pall eBDS (Pall Corporation), both of which allow testing of leukoreduced apheresis as well as whole blood-derived PLTs. After the decision of the AABB to institute universal QC testing of PLT concentrates for evidence of bacterial contamination, in-house validation of the performance of our current blood culture system, the BACTEC 9240, was carried out for this purpose.

STUDY DESIGN AND METHODS

Serial dilutions of nine species of bacteria commonly associated with PLT contamination were prepared in one single-donor apheresis PLT unit per organism. Four mL of dilutions containing less than 1 to greater than 10(3) colony-forming units (CFUs) per mL was inoculated into blood culture bottles (Standard 10 Aerobic/F, Becton-Dickinson Diagnostic Systems) and incubated in a BACTEC 9240 continuously monitored blood culture system. Positive bottles were removed from the system and subcultured to insure the identity of bacterial growth.

RESULTS

With the exception of Streptococcus mitis, the BACTEC system provided a detection sensitivity of less than 10 CFUs per mL for Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Serratia marcescens, Klebsiella pneumoniae, Bacillus cereus, Enterobacter cloacae, and Pseudomonas aeruginosa. The limit of detection for the S. mitis test strain was 61 CFUs per mL. Detection of positive bottles ranged from 6.5 to 17.6 hours depending on the species tested and the cell density of the inoculum. Ongoing use of this system for bacterial detection yielded two true-positive samples from 3879 apheresis PLT products collected at our hospital-based donor center over 9 months.

CONCLUSION

This study validates the use of the BACTEC 9240 continuously monitored blood culture system for the detection of low-level bacterial contamination in single donor apheresis PLTs in less than 24 hours.

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.

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.

Bacterial contamination of blood components

Blood for transfusion is a potential source of infection by a variety of known and unknown transmissible agents. Over the last 20 years, astounding reductions in the risk of viral infection via allogeneic blood have been achieved. As a result of this success, bacterial contamination of blood products has emerged as the greatest residual source of transfusion-transmitted disease. This paper summarizes the current status of detection, prevention, and elimination of bacteria in blood products for transfusion.

A novel method for the detection of bacteria in platelet concentrates utilizing oxygen consumption as a marker for bacterial growth

Bacterial transfusion-transmission remains a significant problem in transfusion medicine. Diversion and improved donor arm disinfection has been introduced by blood services to reduce bacterial transmissions. These interventions are not 100% effective and, therefore, there is still a requirement to screen blood donations, particularly platelet concentrates which are responsible for the majority of transmissions. Pall BDS, a novel bacterial testing system, detects the presence of bacteria in platelet concentrates by measuring the reduction in oxygen content associated with bacterial growth. Buffy coat-derived pooled platelet concentrates were spiked with 12 aerobic and two anaerobic organisms (one species per bag, n = 10) at 100-700 cfu mL(-1). Samples were taken into Pall BDS sample pouches and incubated for 0, 24, 30 and 48 h. An initial incubation was undertaken at 35 degrees C for 24 h and subsequent incubation was at 22 degrees C. At the end of the incubation period the oxygen content in the Pall BDS pouches was measured using a gas analyser. An oxygen content less than or equal to 19.5% was deemed to be positive. Pall BDS pouches tested positive in 80, 94 and 98% units spiked with aerobic bacteria at 24, 30 and 48 h, respectively. Anaerobic bacteria were not detected by the system. Positive BDS pouches contained 10(6) cfu mL(-1) or greater. The system was simple and easy to perform. Pall BDS has a closed sampling system which prevents exogenous contamination. This initial study indicates that the Pall BDS offers a practicable system for detecting bacteria present in leucodepleted platelet concentrates.

Rapid screening method for detection of bacteria in platelet concentrates

Public awareness has long focused on the risks of the transmission of viral agents through blood product transfusion. This risk, however, pales in comparison to the less publicized danger associated with the transfusion of blood products contaminated with bacteria, in particular, platelet concentrates. Up to 1,000 cases of clinical sepsis after the transfusion of platelet concentrates are reported annually in the United States. The condition is characterized by acute reaction symptoms and the rapid onset of septicemia and carries a 20 to 40% mortality rate. The urgent need for a method for the routine screening of platelet concentrates to improve patient safety has long been recognized. We describe the development of a rapid and highly sensitive method for screening for bacteria in platelet concentrates for transfusion. No culture period is required; and the entire procedure, from the time of sampling to the time that the final result is obtained, takes less than 90 min. The method involves three basic stages: the selective removal of platelets by filtration following activation with a monoclonal antibody, DNA-specific fluorescent labeling of bacteria, and concentration of the bacteria on a membrane surface for enumeration by solid-phase cytometry. The method offers a universal means of detection of live, nondividing, or dead gram-negative and gram-positive bacteria in complex cellular blood products. The sensitivity is higher than those of the culture-based methods available at present, with a detection limit of 10 to 10(2) CFU/ml, depending upon the bacterial strain.

Transfusion-transmitted bacterial infection: risks, sources and interventions

Records of the transmission of bacterial infections by transfusion date back to the beginning of organized blood banking. Despite tremendous strides in preventing viral infection through careful donor screening and viral testing, there has been little improvement in reducing the risk of bacterial sepsis since the introduction of closed collection systems. Based on the French Haemovigilance study, the British Serious Hazards of Transmission (SHOT) study and fatality reports to the United States Food and Drug Administration, the risk of clinically apparent sepsis exceeds the risk of HIV, HBV, and HCV transmission. Sources of contamination include the skin, blood, disposables, and the environment. Potential interventions to reduce transfusion-associated bacterial sepsis include improvements to donor arm preparation, diversion of the first aliquot of whole blood, introduction of bacterial testing and/or implementation of pathogen reduction methods.

Estimation of bacterial risk in extending the shelf life of PLT concentrates from 5 to 7 days

BACKGROUND

The use of bacterial culture to prevent bacterial contamination of blood components has renewed interest for extending the shelf life of PLT concentrates to 7 days after collection.

STUDY DESIGN AND METHODS

This study was therefore conducted to determine the residual risk of bacterial contamination in PLT concentrates at the end of 5 and 7 days after collection in a center where all PLT concentrates are routinely screened by taking samples on Day 2 for culture. PLT units with no growth after 48 hours were sampled a second time on Day 5 or Day 7 after collection, followed by inoculation into aerobic culture bottles. The inoculated bottles were then monitored for up to 7 days at 35 degrees C in an automatic monitoring and detection system.

RESULTS

During a 16-month study period, a total of 6020 PLT concentrates were tested 5 days (Group A, n=3010) and 7 days (Group B, n=3010) after collection. Four units in each group (0.133%) were found to be contaminated. In 6 units, bacteria were seen on direct Gram stain. In addition, 5 of the associated RBC units grew the same organisms on culture. The organisms include three coagulase-negative staphylococci and five Propionibacterium acnes. The positive rate of routine short-term bacterial culture was 0.035 percent during the same study period.

CONCLUSION

Despite routine short-term bacterial culture, a significant risk of bacterial contamination remains at 5 and 7 days after collection. For now, the shelf life of PLT concentrates should remain 5 days.

[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.

Bacterial Contamination of Blood Components: Risks, Strategies, and Regulation

Bacterial contamination of transfusion products, especially platelets, is a longstanding problem that has been partially controlled through modern phlebotomy practices, refrigeration of red cells, freezing of plasma and improved materials for transfusion product collection and storage. Bacterial contamination of platelet products has been acknowledged as the most frequent infectious risk from transfusion occurring in approximately 1 of 2,000–3,000 whole-blood derived, random donor platelets, and apheresis-derived, single donor platelets. In the US, bacterial contamination is considered the second most common cause of death overall from transfusion (after clerical errors) with mortality rates ranging from 1:20,000 to 1:85,000 donor exposures. Estimates of severe morbidity and mortality range from 100 to 150 transfused individuals each year.

Concern over the magnitude and clinical relevance of this issue culminated in an open letter calling for the “blood collection community to immediately initiate a program for detecting the presence of bacteria in units of platelets.” Thereafter, the American Association of Blood Banks (AABB) proposed new standards to help mitigate transfusion of units that were contaminated with bacteria. Adopted with a final implementation date of March 1, 2004, the AABB Standard reads “The blood bank or transfusion service shall have methods to limit and detect bacterial contamination in all platelet components.”

This Joint ASH and AABB Educational Session reviews the risks, testing strategies, and regulatory approaches regarding bacterial contamination of blood components to aid in preparing practitioners of hematology and transfusion medicine in understanding the background and clinical relevance of this clinically important issue and in considering the approaches currently available for its mitigation, as well as their implementation.

In this chapter, Drs. Hillyer and Josephson review the background and significance of bacterial contamination, as well as address the definitions, conceptions and limitations of the terms risk, safe and safety. They then describe current transfusion risks including non-infectious serious hazards of transfusion, and current and emerging viral risks. In the body of the text, Dr. Blajchman reviews the prevalence of bacterial contamination in cellular blood components in detail with current references to a variety of important studies. He then describes the signs and symptoms of transfusion-associated sepsis and the sources of the bacterial contamination for cellular blood products including donor bacteremia, and contamination during whole blood collection and of the collection pack. This is followed by strategies to decrease the transfusion-associated morbidity/mortality risk of contaminated cellular blood products including improving donor skin disinfection, removal of first aliquot of donor blood, pre-transfusion detection of bacteria, reducing recipient exposure, and pathogen reduction/inactivation. In the final sections, Drs. Vostal, Epstein and Goodman describe the regulations and regulatory approaches critical to the appropriate implementation of a bacterial contamination screening and limitation program including their and/or the FDA’s input on prevention of bacterial contamination, bacterial proliferation, and detection of bacteria in transfusion products. This is followed by a discussion of sampling strategy for detection of bacteria in a transfusion product, as well as the current approval process for bacterial detection devices, trials recommended under “actual clinical use” conditions, pathogen reduction technologies, and bacterial detection and the extension of platelet storage.

Transfusion medicine for the pediatrician

In the next decade, many of the methodologies and research reviewed in this article will become clinical practice, making the transfusion of blood products safer and more universally available than they are today. NAT will be standard and will surely be performed on each unit of product, PCR testing for pathogens will evolve, and the pathophysiology and immunology of transfusion-related events such as TRALI and immunomodulation will be elucidated. New methods of preservation and early detection of contamination will extend the life of blood products. Red blood cell antigens may be attenuated, making safe products available to more patients. Clinical vigilance at the bedside and in the blood bank will remain key areas for transfusion safety. As I have told many a resident and patient, blood is not saline; there are and will remain risks inherent in this commonly used medical therapy.

Impact of donor arm skin disinfection on the bacterial contamination rate of platelet concentrates

BACKGROUND AND OBJECTIVES

Despite improved methods for detecting bacterial contamination of blood products, bacterial sepsis remains a significant risk in blood transfusion. This study was undertaken to investigate whether adopting a different skin disinfection protocol could reduce the rate of bacterial contamination of platelet concentrates.

MATERIALS AND METHODS

Two skin disinfection protocols were consecutively used in the routine blood collection setting during two 10-month periods: 0.5% cetrimide/0.05% chlorhexidine solution followed by 70% isopropyl alcohol (first 10-month time-period); and 10% povidone-iodine followed by 70% isopropyl alcohol (second 10-month time-period). The rates of bacterial contamination of platelet concentrates were monitored by using a surveillance programme described previously.

RESULTS

The overall bacterial contamination rate in the first time-period was 0.072%. After introduction of the povidone-iodine and isopropyl alcohol protocol, the bacterial contamination rate decreased to 0.042% (relative risk reduction: -0.42; 95% confidence interval, -0.12 to -0.61, P= 0.009). There were no differences in the types of micro-organisms identified (P = 0.7).

CONCLUSIONS

Skin disinfection by povidone-iodine and isopropyl alcohol is more effective than that by cetrimide/chorhexidine and isopropyl alcohol in reducing venepuncture-associated contamination of platelet concentrates by skin flora. Our data indicate that the disinfection protocol should be used on a routine basis and such implementation should translate into a significant improvement in blood safety to patients receiving platelet transfusion.

[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.