Prevention of transfusion of platelet components contaminated with low levels of bacteria: a comparison of bacteria culture and pathogen inactivation methods

Factors Involved in the onset of infection following bacterially contaminated platelet transfusions

Transfusion of platelet concentrates (PCs) is associated with several adverse patient reactions, the most common of which are febrile non-hemolytic transfusion reactions (FNHTRs) and transfusion-associated bacterial-infection/transfusion-associated sepsis (T-ABI/TA-S). Diagnosis of T-ABI/T-AS requires a positive blood culture (BC) result from the transfusion recipient and also a positive identification of bacterial contamination within a test aliquot of the transfused PC. In a significant number of cases, clinical symptoms post-transfusion are reported by the clinician, yet the BCs from the patient and/or PC are negative. The topic of 'missed bacterial detection' has therefore been the focus of several primary research studies and review articles, suggesting that biofilm formation in the blood bag and the presence of viable but non-culturable (VBNC) pathogens are the major causes of this missed detection. However, platelets are emerging as key players in early host responses to infection and as such, the aforementioned biofilm formation could elicit 'platelet priming', which could lead to significant immunological reactions in the host, in the absence of planktonic bacteria in the host bloodstream. This review reflects on what is known about missed detection and relates this to the emerging understanding of the effect of bacterial contamination on the platelets themselves and the significant role played by platelets in exacerbation of an immune response to infection within the transfusion setting.

Pathogen reduction of blood components during outbreaks of infectious diseases in the European Union: an expert opinion from the European Centre for Disease Prevention and Control consultation meeting

Pathogen reduction (PR) of selected blood components is a technology that has been adopted in practice in various ways. Although they offer great advantages in improving the safety of the blood supply, these technologies have limitations which hinder their broader use, e.g. increased costs. In this context, the European Centre for Disease Prevention and Control (ECDC), in co-operation with the Italian National Blood Centre, organised an expert consultation meeting to discuss the potential role of pathogen reduction technologies (PRT) as a blood safety intervention during outbreaks of infectious diseases for which (in most cases) laboratory screening of blood donations is not available. The meeting brought together 26 experts and representatives of national competent authorities for blood from thirteen European Union and European Economic Area (EU/EEA) Member States (MS), Switzerland, the World Health Organization, the European Directorate for the Quality of Medicines and Health Care of the Council of Europe, the US Food and Drug Administration, and the ECDC. During the meeting, the current use of PRTs in the EU/EEA MS and Switzerland was verified, with particular reference to emerging infectious diseases (see Appendix). In this article, we also present expert discussions and a common view on the potential use of PRT as a part of both preparedness and response to threats posed to blood safety by outbreaks of infectious disease.

Bacterial inactivation of platelet concentrates with the THERAFLEX UV-Platelets pathogen inactivation system

BACKGROUND

The THERAFLEX UV-Platelets system (Maco Pharma) uses ultraviolet C (UVC) light for pathogen inactivation (PI) of platelet concentrates (PCs) without any additional photoactive compound. The aim of the study was to systematically investigate bacterial inactivation with this system under conditions of intended use.

STUDY DESIGN AND METHODS

The robustness of the system was evaluated by assessing its capacity to inactivate high concentrations of different bacterial species in accordance with World Health Organization guidelines. The optimal use of the PI system was explored in time-to-treatment experiments by testing its ability to sterilize PCs contaminated with low levels of bacteria on the day of manufacture (target concentration, 100 colony-forming units/unit). The bacteria panel used for spiking experiments in this study included the World Health Organization International Repository Platelet Transfusion Relevant Reference Strains (n = 14), commercially available strains (n = 13), and in-house clinical isolates (n = 2).

RESULTS

Mean log reduction factors after UVC treatment ranged from 3.1 to 7.5 and varied between different strains of the same species. All PCs (n = 12/species) spiked with up to 200 colony-forming units/bag remained sterile until the end of storage when UVC treated 6 hours after spiking. UVC treatment 8 hours after spiking resulted in single breakthrough contaminations with the fast-growing species Escherichia coli and Streptococcus pyogenes.

CONCLUSION

The UVC-based THERAFLEX UV-Platelets system efficiently inactivates transfusion-relevant bacterial species in PCs. The comprehensive data from this study may provide a valuable basis for the optimal use of this UVC-based PI system.

Influence of platelet preparation techniques on in vitro storage quality after psoralen-based photochemical treatment using new processing sets for triple-dose units

BACKGROUND

The INTERCEPT Blood System (IBS) for platelets (PLTs) uses a combination of psoralen and ultraviolet-A light to inactivate pathogens that may contaminate PLT concentrates (PCs). However, no data are available on the quality of IBS-treated PLTs from different apheresis and buffy-coat PC preparation platforms using the new triple storage (TS) set.

STUDY DESIGN AND METHODS

The objective of this study was to evaluate the TS set on three different preparation platforms compared with the large-volume (LV) set, as control. PLT in vitro metabolic and activation parameters were studied over 7 days.

RESULTS

Several statistical differences are observed between the two sets, particularly for pH, oxygen pressure (pO₂ ), carbonic gaz pressure (pCO₂ ), and bicarbonate. The three different preparation techniques influence PLT parameters, and the difference is statistically significant for all the studied parameters, except for pCO₂ . The TS set has the advantage of shorter compound adsorption device time, higher PLT recoveries, and less PLT activation.

CONCLUSION

Results from the measured metabolic parameters and PLT variables obtained from PCs treated by LV and TS sets indicated good PLT function preservation up to 7 days of storage. The in vitro assessment results demonstrated acceptable PLT function for transfusion.

Quality Improvement After Multiple Fatal Transfusion-Transmitted Bacterial Infections

OBJECTIVES

Transfusion-transmitted bacterial infection (TTBI) from platelet components is likely underrecognized and can be fatal. Twenty-four-hour prospective culture was felt to be insufficiently preventive after multiple TTBIs occurred and strategies to improve safety were sought.

METHODS

Two fatal and one severe TTBIs occurred from a split-apheresis platelet donation contaminated with Klebsiella pneumoniae. Improvement opportunities were identified and corrective and preventive action (CAPA) followed.

RESULTS

To mitigate bacterial contamination and improve detection sensitivity, additional prospective culture 48 hours postcollection was implemented. Since implementation, secondary cultures have caught two true positives (0.01%) missed by 24-hour culture. Bacterial testing at issue and pathogen reduction were later implemented as an added layer of safety.

CONCLUSION

While rare, TTBI is a prominent cause of morbidity and mortality from contaminated platelets. The approach to CAPA presented here may lower the risk of future transfusion-transmitted infections but must be weighed against potential added costs.

Inactivated human platelet lysate with psoralen: a new perspective for mesenchymal stromal cell production in Good Manufacturing Practice conditions

BACKGROUND AIMS

Mesenchymal stromal cells (MSC) are ideal candidates for regenerative and immunomodulatory therapies. The use of xenogeneic protein-free Good Manufacturing Practice-compliant growth media is a prerequisite for clinical MSC isolation and expansion. Human platelet lysate (HPL) has been efficiently implemented into MSC clinical manufacturing as a substitute for fetal bovine serum (FBS). Because the use of human-derived blood materials alleviates immunologic risks but not the transmission of blood-borne viruses, the aim of our study was to test an even safer alternative than HPL to FBS: HPL subjected to pathogen inactivation by psoralen (iHPL).

METHODS

Bone marrow samples were plated and expanded in α-minimum essential medium with 10% of three culture supplements: HPL, iHPL and FBS, at the same time. MSC morphology, growth and immunophenotype were analyzed at each passage. Karyotype, tumorigenicity and sterility were analyzed at the third passage. Statistical analyses were performed.

RESULTS

The MSCs cultivated in the three different culture conditions showed no significant differences in terms of fibroblast colony-forming unit number, immunophenotype or in their multipotent capacity. Conversely, the HPL/iHPL-MSCs were smaller, more numerous, had a higher proliferative potential and showed a higher Oct-3/4 and NANOG protein expression than did FBS-MSCs. Although HPL/iHPL-MSCs exhibit characteristics that may be attributable to a higher primitive stemness than FBS-MSCs, no tumorigenic mutations or karyotype modifications were observed.

CONCLUSIONS

We demonstrated that iHPL is safer than HPL and represents a good, Good Manufacturing Practice-compliant alternative to FBS for MSC clinical production that is even more advantageous in terms of cellular growth and stemness.

Validation of an alternative microbiological method for tissue products

According to the European Pharmacopoeia sterility testing of products includes an incubation time of 14 days in thioglycollate medium and soya-bean casein medium. In this case a large period of time is needed for product testing. So we designed a study to evaluate an alternative method for sterility testing. The aim of this study was to reduce the incubation time for the routinely produced products in our tissue bank (cornea and amnion grafts) by obtaining the same detection limit, accurateness and recovery rates as the reference method described in the European Pharmacopoeia. The study included two steps of validation. Primary validation compared the reference method with the alternative method. Therefore eight bacterial and two fungi test strains were tested at their preferred milieu. A geometric dilution series from 10 to 0.625 colony forming unit per 10 ml culture media was used. Subsequent to the evaluation the second part of the study started including the validation of the fertility of the culture media and the parallel testing of the two methods by investigating products. For this purpose two product batches were tested in three independent runs. Concerning the validation we could not find any aberration between the alternative and the reference method. In addition, the recovery rate of each microorganism was between 83.33 and 100 %. The alternative method showed non-inferiority regarding accuracy to the reference method. Due to this study we reduced the sterility testing for cornea and amniotic grafts to 9 days.

Three different bacterial detection systems for platelet concentrates under inter-laboratory conditions

BACKGROUND

A variety of screening methods are currently used worldwide in order to decrease the risk of transfusion-transmitted sepsis and improve the safety of PCs.

METHODS/MATERIALS

PCs inoculated with five different transfusion-relevant species of bacteria at concentrations of 1, 10, and 100 colony-forming units (CFU)ml(-1) were stored at 22°C for 7 days. Flow cytometry (FACS), BacT/Alert automated culturing, and a quantitative real-time PCR (Q-PCR) were then used to detect the presence of bacteria in samples prepared from these PCs.

RESULTS

At the initial spiking concentrations of 1, 10, and 100 CFU ml(-1), Q-PCR detected all five bacterial species tested. Screening with the BacT/Alert culture-based system allowed bacterial detection (inoculated on day 0) within a mean time of 15.13 h for all three spiking concentrations. Using FACS, positive signals were obtained for all three concentrations of Escherichia coli and Bacillus cereus on day 1 and for initial spiking concentrations of Pseudomonas aeruginosa and Staphylococcus aureus of 1 CFU ml(-1) on day 2. For Staphylococcus epidermidis, detection of an initial inoculum of 1 CFU ml(-1) was possible only beginning on day 6.

CONCLUSION

This study shows that under standard laboratory conditions the sensitivity of FACS in the detection of bacterial contamination of PCs was lower than that of either the BacT/Alert automated culturing method or Q-PCR.

Preparation and pathogen inactivation of double dose buffy coat platelet products using the INTERCEPT blood system

Blood centers are faced with many challenges including maximizing production yield from the blood product donations they receive as well as ensuring the highest possible level of safety for transfusion patients, including protection from transfusion transmitted diseases. This must be accomplished in a fiscally responsible manner which minimizes operating expenses including consumables, equipment, waste, and personnel costs, among others. Several methods are available to produce platelet concentrates for transfusion. One of the most common is the buffy coat method in which a single therapeutic platelet unit (≥ 2.0 x10(11) platelets per unit or per local regulations) is prepared by pooling the buffy coat layer from up to six whole blood donations. A procedure for producing "double dose" whole blood derived platelets has only recently been developed. Presented here is a novel method for preparing double dose whole blood derived platelet concentrates from pools of 7 buffy coats and subsequently treating the double dose units with the INTERCEPT Blood System for pathogen inactivation. INTERCEPT was developed to inactivate viruses, bacteria, parasites, and contaminating donor white cells which may be present in donated blood. Pairing INTERCEPT with the double dose buffy coat method by utilizing the INTERCEPT Processing Set with Dual Storage Containers (the "DS set"), allows blood centers to treat each of their double dose units in a single pathogen inactivation processing set, thereby maximizing patient safety while minimizing costs. The double dose buffy coat method requires fewer buffy coats and reduces the use of consumables by up to 50% (e.g. pooling sets, filter sets, platelet additive solution, and sterile connection wafers) compared to preparation and treatment of single dose buffy coat platelet units. Other cost savings include less waste, less equipment maintenance, lower power requirements, reduced personnel time, and lower collection cost compared to the apheresis technique.

Photoinduced damage to cellular DNA: direct and photosensitized reactions

The survey focuses on recent aspects of photochemical reactions to cellular DNA that are implicated through the predominant formation of mostly bipyrimidine photoproducts in deleterious effects of human exposure to sunlight. Recent developments in analytical methods have allowed accurate and quantitative measurements of the main DNA photoproducts in cells and human skin. Highly mutagenic CC and CT bipyrimidine photoproducts, including cyclobutane pyrimidine dimers and pyrimidine (6-4) pyrimidone photoproducts (6-4PPs) are generated in low yields with respect to TT and TC photoproducts. Another striking finding deals with the formation of Dewar valence isomers, the third class of bipyrimidine photoproducts that is accounted for by UVA-mediated isomerization of initially UVB generated 6-4PPs. Cyclobutadithymine (T<>T) has been unambiguously shown to be involved in the genotoxicity of UVA radiation. Thus, T<>T is formed in UVA-irradiated cellular DNA according to a direct excitation mechanism with a higher efficiency than oxidatively generated DNA damage that arises mostly through the Type II photosensitization mechanism. C<>C and C<>T are repaired at rates intermediate between those of T<>T and 6-4TT. Evidence has been also provided for the occurrence of photosensitized reactions mediated by exogenous agents that act either in an independent way or through photodynamic effects.

Oxygen measurements in platelet fluids - a new non-invasive method to detect bacterial contaminations in platelets

BACKGROUND

The residual risk for bacterial contamination in blood components especially in platelets is one to two orders of magnitude higher than for transfusion relevant viral infections. The majority of all bacterial transmitted fatalities occurred at the end of platelet shelf life. Therefore, the maximum shelf life of platelet concentrates (PC) was reduced to 4 days after blood donation in Germany in 2008.

METHODS

A new continuous non-invasive bacterial detection method was developed by O(2) measurements in the platelet fluids and tested with 10 transfusion relevant bacteria species.

RESULTS

The bacterial concentration at the time point of a positive signal of PreSense O(2) ranged between 10(2) and 10(5) CFU mL(-1) . Harmful transfusion-transmitted bacterial infection would have probably been prevented by this novel technology. Only strict anaerobic bacteria strains like Clostridium perfringens were not detected within the study period of 72 h.

CONCLUSIONS

The described non-invasive bacterial detection method represents a new approach to prevent transmission of bacterial infection in platelets. The method is characterised by the advantage that all investigations can be performed until right up to the time of transfusion, and therefore, reduce the risk for sample errors to a minimum.

Photochemical inactivation of Pseudomonas aeruginosa

Adaptability to a broad range of environments together with relatively high resistance to antibiotics and to disinfectants makes Pseudomonas aeruginosa a concern in hospitals and in public health. We investigated whether UVA-mediated photochemical inactivation of P. aeruginosa could be accomplished with high efficiency while at the same time preserving the sensitivity of subsequent diagnostic tests. We characterized dose responses and bactericidal kinetic rates of 5-iodonaphthyl 1-azide (INA) and of amotosalen (AMO) as these substances exposed to UVA are known to inactivate germs with minimal impact to blood products or to viral antigens. Neither UVA without photochemicals nor INA or AMO in the dark inactivated bacteria. We found that AMO was ca 1000-fold more effective in inactivating P. aeruginosa cells than INA under similar conditions. Photoinactivation with either INA or AMO at conditions that abolished bacterial infectivity did not impair polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) testing. For comparison, similar titers of Bacillus atrophaeus spores (a surrogate for B. anthracis) remained unaffected at conditions that reduced the survival of P. aeruginosa below detection levels. The results presented in this study should assist in improved methods to inactivate P. aeruginosa in environmental, clinical and forensic samples without impairing subsequent nucleic acid- or immune-based analysis.

Pathogen-inactivation of platelet components with the INTERCEPT Blood System ™: a cohort study

INTRODUCTION

INTERCEPT treatment is used to reduce platelet transfusion associated bacterial infections. Limited data are available in Switzerland.

PATIENTS AND METHODS

Patients with thrombocytopenia or thrombocyte dysfunction requiring platelet transfusions were enrolled in a prospective cohort study on safety (primary endpoint) and efficacy (secondary endpoint) of INTERCEPT treated platelets (I-PLTs). I-PLTs were produced from double-dose apheresis products. Data on safety were actively recorded for each transfusion.

RESULTS

A total of 551 I-PLT units (mean platelet dose: 2.6 ± 0.4 × 10(11)/unit) were transfused to 46 patients (mean number of platelet transfusions per patient: 12 ± 12.5). Fifty-one (9%) transfusions were associated with adverse events and 12 (2%) with acute transfusion reactions. Eleven serious adverse events were observed, none considered as related to the administration of I-PLT. Mean 1-4h and 16-24h CCIs were 10.1 ± 8.1 and 3.6 ± 6.6, respectively.

CONCLUSION

The transfusion of I-PLT was associated with a good safety profile and adequate platelet count increments at 1-4h.

Laboratory Evaluation of the Effectiveness of Pathogen Reduction Procedures for Bacteria

SUMMARY: Bacterial contamination remains a leading factor for transfusion-associated serious morbidity and mortality. Pathogen reduction procedures offer a pro-active approach to prevent bacterial contamination of cellular blood components and especially of platelet concentrates. In the past, the laboratory evaluation of the effectiveness of the pathogen reduction procedures to minimise the bacterial load of blood components has been primarily based on log reduction assays similar to the assessment of antiviral activities. Bacteria strains with the ability to multiply in the blood components are seeded in highest possible cell numbers, the pathogen reduction procedure is applied, and the post-treatment number of bacteria is measured. The effectiveness of the procedure is characterised by calculating the log reduction of the post- to pre-treatment bacteria titres. More recently, protocols have been developed for experiments starting with a low bacteria load and monitoring the sterility of the blood component during the entire storage period of the blood component. Results for 3 different pathogen reduction technologies in these experimental models are compared and critical determinants for the results are addressed. The heterogeneity of results observed for different strains suggests that the introduction of international transfusion-relevant bacterial reference strains may facilitate the validity of findings in pathogen reduction experiments.

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

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

Establishment of the first international repository for transfusion-relevant bacteria reference strains: ISBT working party transfusion-transmitted infectious diseases (WP-TTID), subgroup on bacteria

BACKGROUND

Bacterial contamination of platelet concentrates (PCs) still remains a significant problem in transfusion with potential important clinical consequences, including death. The International Society of Blood Transfusion Working Party on Transfusion-Transmitted Infectious Diseases, Subgroup on Bacteria, organised an international study on Transfusion-Relevant Bacteria References to be used as a tool for development, validation and comparison of both bacterial screening and pathogen reduction methods.

MATERIAL AND METHODS

Four Bacteria References (Staphylococcus epidermidis PEI-B-06, Streptococcus pyogenes PEI-B-20, Klebsiella pneumoniae PEI-B-08 and Escherichia coli PEI-B-19) were selected regarding their ability to proliferate to high counts in PCs and distributed anonymised to 14 laboratories in 10 countries for identification, enumeration and bacterial proliferation in PCs after low spiking (0·3 and 0·03 CFU/ml), to simulate contamination occurring during blood donation.

RESULTS

Bacteria References were correctly identified in 98% of all 52 identifications. S. pyogenes and E. coli grew in PCs in 11 out of 12 laboratories, and K. pneumoniae and S. epidermidis replicated in all participating laboratories. The results of bacterial counts were very consistent between laboratories: the 95% confidence intervals were for S. epidermidis: 1·19-1·32 × 10(7) CFU/ml, S. pyogenes: 0·58-0·69 × 10(7) CFU/ml, K. pneumoniae: 18·71-20·26 × 10(7) CFU/ml and E. coli: 1·78-2·10 × 10(7) CFU/ml.

CONCLUSION

The study was undertaken as a proof of principle with the aim to demonstrate (i) the quality, stability and suitability of the bacterial strains for low-titre spiking of blood components, (ii) the property of donor-independent proliferation in PCs, and (iii) their suitability for worldwide shipping of deep frozen, blinded pathogenic bacteria. These aims were successfully fulfilled. The WHO Expert Committee Biological Standardisation has approved the adoption of these four bacteria strains as the first Repository for Transfusion-Relevant Bacteria Reference Strains and, additionally, endorsed as a project the addition of six further bacteria strain preparations suitable for control of platelet contamination as the next step of enlargement of the repository.

Extension of platelet shelf life from 4 to 5 days by implementation of a new screening strategy in Germany

BACKGROUND

The Paul-Ehrlich-Institute analysed all fatalities due to bacterial infections between 1997 and 2007. Thereafter, the platelet shelf life was reduced to a maximum of 4 days after blood donation because the majority of all cases of severe transfusion-transmitted bacterial infections occurred with day 5 platelets. The current study compares the analytical sensitivity and the diagnostic specificity of four rapid bacterial detection procedures.

METHODS

Nine transfusion-relevant bacterial strains were spiked in pooled platelets or apheresis platelets at a low concentration (10 CFU/bag). Samples were collected after day 3, day 4 and day 5 and investigated by four rapid bacterial detection methods (modified BacT/ALERT, Bactiflow, FACS method and 16s DNA PCR methods).

RESULTS

Seven out of nine bacterial strains were adequately detected by BacT/ALERT, Bactiflow and PCR in apheresis platelets and pooled platelets after sample collection at day 3, day 4 and day 5. For three bacterial strains, analytical sensitivity was reduced for the FACS method. Two bacterial strains did not grow under the storage conditions in either pooled or apheresis platelets.

CONCLUSIONS

A late sample collection on day 3, day 4 or day 5 after blood donation in combination with a rapid bacterial detection method offers a new opportunity to improve blood safety and reduce errors due to sampling., BacT/ALERT, Bactiflow or 16s ID-NAT are feasible for late bacterial screening in platelets may provide data which support the extension of platelet shelf life in Germany to 5 days.

Pathogen Inactivation of Platelet and Plasma Blood Components for Transfusion Using the INTERCEPT Blood System™

BACKGROUND: The transmission of pathogens via blood transfusion is still a major threat. Expert conferences established the need for a pro-active approach and concluded that the introduction of a pathogen inactivation/reduction technology requires a thorough safety profile, a comprehensive pre-clinical and clinical development and an ongoing hemovigilance program. MATERIAL AND METHODS: The INTERCEPT Blood System utilizes amotosalen and UVA light and enables for the treatment of platelets and plasma in the same device. Preclinical studies of pathogen inactivation and toxicology and a thorough program of clinical studies have been conducted and an active he-movigilance-program established. RESULTS: INTERCEPT shows robust efficacy of inactivation for viruses, bacteria (including spirochetes), protozoa and leukocytes as well as large safety margins. Furthermore, it integrates well into routine blood center operations. The clinical study program demonstrates the successful use for very diverse patient groups. The hemovigilance program shows safety and tolerability in routine use. Approximately 700,000 INTERCEPT-treated products have been transfused worldwide. The system is in clinical use since class III CE-mark registration in 2002. The safety and efficacy has been shown in routine use and during an epidemic. CONCLUSION: The INTERCEPT Blood System for platelets and plasma offers enhanced safety for the patient and protection against transfusion-transmitted infections.

Real-Time Live Confocal Fluorescence Microscopy as a New Tool for Assessing Platelet Vitality

BACKGROUND: Assessment of platelet vitality is important for patients presenting with inherited or acquired disorders of platelet function and for quality assessment of platelet concentrates. METHODS: Herein we combined live stains with intra-vital confocal fluorescence microscopy in order to obtain an imaging method that allows fast and accurate assessment of platelet vitality. Three fluorescent dyes, FITC-coupled wheat germ agglutinin (WGA), tetramethylrhodamine methyl ester perchlorate (TMRM) and acetoxymethylester (Rhod-2), were used to assess platelet morphology, mitochondrial activity and intra-platelet calcium levels. Microscopy was performed with a microlens-enhanced Nipkow spinning disk-based system allowing live confocal imaging. RESULTS: Comparison of ten samples of donor platelets collected before apheresis and platelets collected on days 5 and 7 of storage showed an increase in the percentage of Rhod-2-positive platelets from 3.6 to 47 and finally to 71%. Mitochondrial potential was demonstrated in 95.4% of donor platelets and in 92.5% of platelets stored for 7 days. CONCLUSION: Such fast and accurate visualization of known key parameters of platelet function could be of relevance for studies addressing the quality of platelets after storage and additional manipulation, such as pathogen inactivation, as well as for the analysis of inherited platelet function disorders.

The Pan Genera Detection immunoassay: a novel point-of-issue method for detection of bacterial contamination in platelet concentrates

Bacterial contamination of platelet concentrates (PCs) still represents an ongoing risk in transfusion-transmitted sepsis. Recently the Pan Genera Detection (PGD) system was developed and FDA licensed for screening of bacterial contamination of PCs directly prior to transfusion. The test principle is based on the immunological detection of lipopolysaccharide (for Gram-negative bacteria) or lipoteichoic acid (for Gram-positive bacteria). In the present study we analyzed the applicability of this method with regard to detection limit, practicability, implementation, and performance. PCs were spiked with Staphylococcus aureus, Bacillus subtilis, and five different Klebsiella pneumoniae strains, as well as eight different Escherichia coli strains. The presence of bacteria was assessed by the PGD immunoassay, and bacteria were enumerated by plating cultures. Application of the PGD immunoassay showed that it is a rapid test with a short hands-on time for sample processing and no demand for special technical equipment and instrument operation. The lower detection limits of the assay for Gram-positive bacteria showed a good agreement with the manufacturer's specifications (8.2 × 10(3) to 5.5 × 10(4) CFU/ml). For some strains of K. pneumoniae and E. coli, the PGD test showed analytical sensitivities (>10(6) CFU/ml) that were divergent from the designated values (K. pneumoniae, 2.0 × 10(4) CFU/ml; E. coli, 2.8 × 10(4) CFU/ml). Result interpretation is sometimes difficult due to very faint bands. In conclusion, our study demonstrates that the PGD immunoassay is an easy-to-perform bedside test for the detection of bacterial contamination in PCs. However, to date there are some shortcomings in the interpretation of results and in the detection limits for some strains of Gram-negative bacteria.

Novel flow cytometry-based screening for bacterial contamination of donor platelet preparations compared with other rapid screening methods

BACKGROUND

Bacterial contamination is the major infectious hazard associated with transfusion of platelet preparations (PLTs). Routine testing for bacterial contamination in PLTs has become common, but transfusion-transmitted bacterial sepsis has not been eliminated. Here, we describe a novel flow cytometry-based method for point-of-issue screening of PLTs for bacterial contamination.

METHODS

We used the BactiFlow flow cytometer to detect and count bacteria based on esterase activity in viable cells. We compared the assay to incubation (BacT/Alert culture system) and rapid nucleic acid-based or immunoassay (reverse transcription PCR, Pan Genera Detection) methods.

RESULTS

We established a protocol for bacterial screening of PLTs consisting of enzymatic digestion and centrifugal filtration for the elimination of viable platelets and selective labeling of bacteria with fluorescent esterase substrate (ChemChrome V23). Results from the BactiFlow showed an excellent correlation (r = 0.9923 E. coli, r = 0.9736 S. epidermidis) to traditional plate count results. The lower detection limit of the assay was determined to be 150 CFU/mL, and the time to result was <1 h.

CONCLUSIONS

Our study demonstrates that BactiFlow flow cytometry is suitable for rapid screening of PLTs for bacterial contamination and fulfils the requirements for a point-of-issue testing of PLTs with acceptable time to result, specificity, sensitivity, and cost.

Glycans and glycosylation of platelets: current concepts and implications for transfusion

PURPOSE OF REVIEW

Platelet products are currently stored at room temperature, because refrigeration causes their rapid clearance from the circulation upon transfusion. Glycans have recently been emphasized as important determinants for the clearance of refrigerated platelets. The present review addresses the current knowledge of platelet glycans and the potential of glycosylation for improving platelet storage.

RECENT FINDINGS

Removal of refrigerated platelets from the circulation is partly mediated by recognition of clustered beta-N-acetylglucosamine on platelet surface glycoproteins by the alphaMbeta2 hepatic lectin receptor. Capping the exposed beta-N-acetylglucosamine residues by enzymatic galactosylation restored the circulation of short-term chilled murine platelets, introducing a novel method that allows for cold storage of platelet. Recent studies have, however, shown that galactosylation is not sufficient to restore circulation of long-term refrigerated platelets. Additional data indicate that differential carbohydrate-mediated mechanisms may exist for clearance of short-term and long-term cold-stored platelets.

SUMMARY

Room temperature storage of platelet products increases the risk of transfusion-mediated sepsis and accelerates platelet deterioration, limiting platelet shelf life. Recent evidence suggests that glycoengineering of platelets might allow for their cold storage, significantly improving the quality of platelet products.

Spore-forming organisms in platelet concentrates: a challenge in transfusion bacterial safety

Bacterial detection and pathogen reduction are widely used methods of minimizing the risk of transfusion-transmitted bacterial infection. But, bacterial spores are highly resistant to chemical and physical agents. In this study, we assessed the bacterial proliferation of spore-forming organisms seeded into platelet concentrates (PCs) to demonstrate that spores can enter the vegetative state in PCs during storage. In the in vitro study, PCs were inoculated with 1-10 spores mL(-1)of Bacillus cereus (n = 1), Bacillus subtilis (n = 2) and Clostridium sporogenes (n = 2). Sampling was performed during 6-day aerobic storage at 22 degrees C. The presence of bacteria was assessed by plating culture, automated culture and real-time reverse transcriptase-polymerase chain reaction (RT-PCR). Spores of the C. sporogenes do not enter the vegetative phase under PC storage conditions, whereas B. subtilis and B. cereus showed growth in the PC and could be detected using RT-PCR and automated culture. Depending on the species and inoculums, bacterial spores may enter the vegetative phase during PC storage and can be detected by bacterial detection methods.

Platelet storage lesion: a new understanding from a proteomic perspective

Platelet storage and availability for the purposes of transfusion are currently restricted by a markedly short shelf life of 5 to 7 days owing to an increased risk of bacterial growth and storage-related deterioration called the platelet storage lesion. Because most bacteria grow to confluence within 5 days during storage at room temperature, there is little increased risk of bacterial overgrowth with testing in place, and the only remaining issue is the quality of platelets during the extended storage. Although the manifestations of the storage lesion have been well studied using a variety of in vitro measures, the precise biochemical pathways involved in the initiation and progression of this process have yet to be identified. Proteomics has emerged as a powerful tool to identify and monitor changes during platelet storage and, in combination with biochemical and physiologic studies, facilitates the development of a sophisticated mechanistic view. In this review, we summarize recent experimental work that has led to a detailed overview of protein changes linked to platelet functions and signaling pathways, providing potential targets for inhibitors to ameliorate the storage lesion.

Quantitative analysis of DNA interstrand cross-links and monoadducts formed in human cells induced by psoralens and UVA irradiation

Upon exposure to UVA light, psoralens can induce DNA interstrand cross-links (ICLs), which can block DNA replication and transcription. Among the psoralen derivatives, 8-methoxypsoralen (8-MOP) is conventionally applied for psoriasis therapy, and amotosalen S59 is used to inactivate bacterial and viral pathogens in blood components. In addition to the ICL formation, psoralens also readily form various monoadducts (MAs) with thymidine residues in DNA when exposed to UVA light, and the biological implications for these monoadducts remain unclear. Here, we reported a method that encompassed digestion with a single enzyme (nuclease P1) and LC-MS/MS, for the simultaneous quantification of ICL and MAs induced in human cells exposed with 8-MOP or S59 and UVA light. Our results showed that the yield of ICL induced by S59, which increased from 3.9 to 12.8 lesions/10(3) nucleotides as the dose of UVA light increased from 0.5 to 10.0 J/cm(2), was approximately 100 fold more than that induced by 8-MOP. In addition, three and five products were identified as 8-MOP- and S59-MAs, respectively, and the yields of MAs were significantly lower than that for ICL. The yields of the three 8-MOP-MAs were 7.6-2.2, 1.9-9.9, and 7.2-51 per 10(6) nucleotides and those of the five S59-MAs were 215-19, 106-39, 25-21, 32-146, and 22-26 per 10(6) nucleotides as the dose of UVA light increased from 0.5 to 10.0 J/cm(2). Although the yields of MAs induced by 8-MOP and S59 were lower than those of the respective ICLs under the same exposure conditions, the formation of appreciable amounts of MAs might account for some of the mutations induced by psoralens.

Propionibacterium acnes lacks the capability to proliferate in platelet concentrates

BACKGROUND AND OBJECTIVES

Propionibacterium acnes is considered to be one of the most frequent contaminants of platelet concentrates (PCs) when anaerobic culture-based detection methods are used. But Propionibacteria are often detected too late when blood products have already been transfused. Therefore, its transfusion relevance is still demanding clarification because studies of the outcome of patients transfused with P. acnes-contaminated PCs are still uncommon. In this study, we monitored clinical effects in patients after transfusion of PCs, which were detected too late in sterility testing. Furthermore, we assessed the bacterial proliferation of Propionibacterium species seeded into PCs to clarify their significance for platelet bacteria screening.

MATERIALS AND METHODS

In the look-back process, we followed the route of the putative contaminated PC units from storage to transfusion. In the in vitro study, PCs were inoculated with 1-100 colony-forming unit (CFU)/ml of clinical isolates of Propionibacteria (n = 10). Sampling was performed during 10-day aerobic storage at 22 degrees C. The presence of bacteria was assessed by plating culture and automated BacT/Alert culture system.

RESULTS

Propionibacterium acnes shows slow or no growth under PC storage conditions. Clinical signs of adverse events after transfusion of potentially contaminated PC units were not reported.

CONCLUSION

Propionibacteria do not proliferate under PC storage conditions and therefore may be missed or detected too late when blood products have already been transfused.