Characterization of a canine freeze-dried platelet-derived hemostatic agent: A preclinical model for surgical and traumatic hemorrhage

INTRODUCTION

A freeze-dried, platelet-derived hemostatic agent (FPH) was developed for acute hemorrhage. The canine product (cFPH) was developed for use in preclinical models supporting human product (hFPH) investigations.

MATERIALS AND METHODS

A carotid artery bypass graft (CABG) study in dogs compared 3 dosages of cFPH to canine liquid stored platelets (cLSP) and vehicle (VEH) control groups. Histopathological analysis and blood loss assessments were completed. A separate ex-vivo synthetic graft study assessed thrombogenicity via blood from human and canine donors that was combined with species-specific FPH or apheresis platelets. Characterization of cFPH and hFPH included thrombin generation, total thrombus formation, and scanning electron microscopy.

RESULTS

Blood loss was reduced in CABG dogs receiving standard of care (cLSP) or cFPH treatment compared to VEH control; a cFPH dose effect signal was observed. Further, cFPH dosing up to 5 × 109 cells/kg was not associated with increased mortality or occlusion of the anastomosis sites, and histopathologic evidence of off-target thrombosis was not detected. When passed through a synthetic graft (ex vivo), whole blood combined with species-specific FPH did not result in thrombosis beyond that of whole blood control. In vitro testing and imaging of cFPH and FPH were comparable.

CONCLUSIONS

A single dose of cFPH or cLSP reduced blood loss in a pilot surgical study and was well tolerated with no related adverse events. Further, the hemostatic activity and characteristics of cFPH are comparable to that of hFPH, suggesting that research findings from the canine product are likely to inform the development of the human product.

What's in Your Transfusion? A Bedside Guide to Blood Products and Their Preparation

An understanding of the contents of blood products and how they are modified before transfusion will help any physician. This article will review five basic blood products and the five most common product modifications.

Hemovigilance data: An effective approach for evaluating bacterial protection systems for platelet transfusions

BACKGROUND AND OBJECTIVE

Septic transfusion reactions due to bacterial contamination in platelet concentrates (PCs) are continually reported to hemovigilance (HV) programs. Worldwide, blood centers use different systems to avoid transfusion-associated bacterial sepsis in PCs. Herein, national HV data were gathered to compare bacterial protection systems and to assess the risk of bacterial contamination.

MATERIALS AND METHODS

HV data with definite transfusion-associated bacterial sepsis in PCs were obtained from Australia, Canada, the United Kingdom (U. K.), and Switzerland between 2006 and 2016. These data were reviewed to evaluate bacterial protection systems including early small-volume (ESV), early large-volume (ELV), and delayed large-volume (DLV) bacterial culture screening and pathogen inactivation (PI) treatment.

RESULTS

Implementation of DLV bacterial culture screening in the U. K. and PI treatment in Switzerland resulted in significant reductions (P < 0.05) in transfusion-associated bacterial sepsis for the period of 2011-2016 compared to the prior 4 years (2006-2010). Approximately 1.86 million DLV bacterial culture-screened PCs and 0.21 million PI-treated PCs were issued with no reported septic fatalities nor cases of life-threatening sepsis. In Australia, two life-threatening septic transfusion reactions (1.923 per million) were reported out of almost 1.04 million ELV bacterial culture-screened PCs, and no septic fatalities were reported. Meanwhile, in Canada, four life-threatening septic transfusion reactions (3.6/million) and one fatality (0.9/million) were observed in about 1.11 million ESV bacterial culture-screened PCs.

CONCLUSION

DLV bacterial culture and PI treatment significantly reduced the incidence of septic reactions. The advantages and disadvantages of both systems merit further investigation before implementation.

Characterization of the Antibacterial Activity of an SiO2 Nanoparticular Coating to Prevent Bacterial Contamination in Blood Products

Technological innovations and quality control processes within blood supply organizations have significantly improved blood safety for both donors and recipients. Nevertheless, the risk of transfusion-transmitted infection remains non-negligible. Applying a nanoparticular, antibacterial coating at the surface of medical devices is a promising strategy to prevent the spread of infections. In this study, we characterized the antibacterial activity of an SiO₂ nanoparticular coating (i.e., the “Medical Antibacterial and Antiadhesive Coating” [MAAC]) applied on relevant polymeric materials (PM) used in the biomedical field. Electron microscopy revealed a smoother surface for the MAAC-treated PM compared to the reference, suggesting antiadhesive properties. The antibacterial activity was tested against selected Gram-positive and Gram-negative bacteria in accordance with ISO 22196. Bacterial growth was significantly reduced for the MAAC-treated PVC, plasticized PVC, polyurethane and silicone (90–99.999%) in which antibacterial activity of ≥1 log reduction was reached for all bacterial strains tested. Cytotoxicity was evaluated following ISO 10993-5 guidelines and L929 cell viability was calculated at ≥90% in the presence of MAAC. This study demonstrates that the MAAC could prevent bacterial contamination as demonstrated by the ISO 22196 tests, while further work needs to be done to improve the coating processability and effectiveness of more complex matrices.

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.

Spontaneous and recurrent subdural haematoma in a patient with May-Hegglin anomaly

Both acute and chronic subdural haematomas typically occur following trauma. Non-traumatic causes are less common, but aetiologies include arteriovenous malformation, intracranial aneurysm rupture, tumour-associated haemorrhage and coagulopathies. May-Hegglin anomaly is an example of a coagulopathy, which is caused by a mutation in the gene encoding non-muscle myosin heavy chain 9 (MYH9) and therefore falls into a group of diseases referred to as MYH9-related diseases (MYH9-RD). The symptomology of MYH9-RD is often mild, and patients tend to experience epistaxis, gingival bleeding and bruising. Life-threatening haemorrhage rarely occurs. In this short report, we describe a patient with known May-Hegglin anomaly who presented with a potentially life-threatening, spontaneous subdural haematoma requiring surgery on two occasions. This is only the second such report in the literature, and the first of spontaneous and recurrent haemorrhage in association with May-Hegglin anomaly.

Scalable Production of Equine Platelet Lysate for Multipotent Mesenchymal Stromal Cell Culture

Translation of multipotent mesenchymal stromal cell (MSC)-based therapies is advancing in human and veterinary medicine. One critical issue is the in vitro culture of MSC before clinical use. Using fetal bovine serum (FBS) as supplement to the basal medium is still the gold standard for cultivation of many cell types including equine MSC. Alternatives are being explored, with substantial success using platelet lysate-supplemented media for human MSC. However, progress lags behind in the veterinary field. The aim of this study was to establish a scalable protocol for equine platelet lysate (ePL) production and to test the ePL in equine MSC culture. Whole blood was harvested into blood collection bags from 20 healthy horses. After checking sample materials for pathogen contamination, samples from 19 animals were included. Platelet concentrates were prepared using a buffy coat method. Platelets, platelet-derived growth factor BB, and transforming growth factor β1 concentrations were increased in the concentrates compared with whole blood or serum (p < 0.05), while white blood cells were reduced (p < 0.05). The concentrates were lysed using freeze/thaw cycles, which eliminated the cells while growth factor concentrations were maintained. Donor age negatively correlated with platelet and growth factor concentrations after processing (p < 0.05). Finally, all lysates were pooled and the ePL was evaluated as culture medium supplement in comparison with FBS, using adipose-derived MSC from four unrelated donor horses. MSC proliferated well in 10% FBS as well as in 10% ePL. However, using 5 or 2.5% ePL entailed highly inconsistent proliferation or loss of proliferation, with significant differences in generation times and confluencies (p < 0.05). MSC expressed the surface antigens CD90, CD44, and CD29, but CD73 and CD105 detection was low in all culture media. Adipogenic and osteogenic differentiation led to similar results in MSC from different culture media. The buffy coat method is useful to produce equine platelet concentrate with increased platelet and reduced white blood cell content in large scales. The ePL obtained supports MSC expansion similar as FBS when used at the same concentration (10%). Further investigations into equine MSC functionality in culture with ePL should follow.

A dual-center evaluation of platelet culture vials to detect the presence of microorganisms in platelets

BACKGROUND

Microorganism contamination of platelets results in a high risk of transfusion-related sepsis. Here, the ability of culture vials (BD BACTEC Platelet Aerobic/F and Platelet Anaerobic/F vials, Becton, Dickinson and Company) to detect microorganisms in leukoreduced apheresis platelets (LRAPs) and leukoreduced whole blood platelet concentrates (LRWBPCs) was assessed.

METHODS

LRAPs or LRWBPCs were inoculated into Aerobic/F and Anaerobic/F vials and placed in a blood culturing system (BD BACTEC FX System, Becton, Dickinson and Company) for growth/monitoring over 7 days to detect preexisting contamination during false-positive testing. Subsequently, platelets were seeded with microorganisms at approximately 10 CFU/mL or approximately 1 CFU/mL to simulate contamination. Aerobic/F and Anaerobic/F vials were inoculated with platelets (sets of 12). Microorganism growth was detected in the BACTEC FX instrument over 7 days. Overall, 2925 vials were tested.

RESULTS

Of the 1905 vials included in the microorganism detection phase, 63 (3.3%) Aerobic/F and 16 (0.8%) Anaerobic/F vials were both BACTEC FX and subculture negative. From the remaining 1827 vials, two (0.1%) Anaerobic/F vials were false positive; no false positives were observed in Aerobic/F vials, and no false negatives occurred in either vial type. Of the remaining 1825 vials (99.9%), 955 Aerobic/F and 870 Anaerobic/F vials were true positives. The mean-time-to-detection range was 8.5 to 77 hours. All true-positive Aerobic/F and Anaerobic/F vials showed 100% agreement with subculture for positive identification of seeded microorganisms.

CONCLUSION

Aerobic/F and Anaerobic/F vials facilitate contamination detection in LRAPs and LRWBPCs down to approximately 1 CFU/mL. These results support the use of Aerobic/F and Anaerobic/F vials for quality control testing of platelets before transfusion.

Ensuring safety of the blood supply in the United States: Donor screening, testing, emerging pathogens, and pathogen inactivation

Safety of the blood supply has been a critical aspect of the transfusion medicine field since its inception, including infections that can be passed to a blood product recipient. Reactive efforts to identify potentially infected blood products are used throughout the blood donation process and afterward. Before donation, potential donors are provided educational materials about infection risks, examined and then screened through a series of questions that help temporarily, permanently, or indefinitely defer donors who could harbor acute and/or chronic infections. During donation, aseptic technique and diversion pouches reduce the potential to introduce bacteria into the blood product. Before transfusion, the blood products are tested for several infectious diseases by serology, nucleic acid testing, or a combination. During transfusion, the patient is monitored closely, and suspected transfusion reactions should be reported and investigated. The FDA regularly publishes guidance documents to incorporate knowledge gained regarding transfusion-transmitted infections, so that information can be shared and practices updated so that transfusion-related patient care can be optimized over time. Pathogen reduction processes are being developed and deployed that provide a proactive approach to both recognized and emerging pathogens.

The design of an adaptive clinical trial to evaluate the efficacy of platelets stored at low temperature in surgical patients

BACKGROUND

Storage of platelets at 4°C compared with 22°C may increase both hemostatic activity and storage duration; however, the maximum duration of cold storage is unknown. We report the design of an innovative, prospective, randomized, Bayesian adaptive, "duration finding" clinical trial to evaluate the efficacy and maximum duration of storage of platelets at 4°C.

METHODS

Patients undergoing cardiac surgery and requiring platelet transfusions will be enrolled. Patients will be randomized to receive platelets stored at 22°C up to 5 days or platelets stored at 4°C up to 5 days, 10 days, or 15 days. Longer durations of cold storage will only be used if shorter durations at 4°C appear noninferior to standard storage, based on a four-level clinical hemostatic efficacy score with a NIM of a half level. A Bayesian linear model is used to estimate the hemostatic efficacy of platelet transfusions based on the actual duration of storage at 4°C.

RESULTS

The type I error rate, if platelets stored at 4°C are inferior, is 0.0247 with an 82% probability of early stopping for futility. With a maximum sample size of 1,500, the adaptive trial design has a power of over 90% to detect noninferiority and a high probability of correctly identifying the maximum duration of storage at 4°C that is noninferior to 22°C.

CONCLUSION

An adaptive, duration-finding trial design will generate Level I evidence and allow the determination of the maximum duration platelet storage at 4°C that is noninferior to standard storage at 22°C, with respect to hemostatic efficacy. The adaptive trial design helps to ensure that longer cold storage durations are only explored once substantial supportive data are available for the shorter duration(s) and that the trial stops early if continuation is likely to be futile.

Red blood cells treated with the amustaline (S-303) pathogen reduction system: a transfusion study in cardiac surgery

BACKGROUND

Nucleic acid-targeted pathogen inactivation technology using amustaline (S-303) and glutathione (GSH) was developed to reduce the risk of transfusion-transmitted infectious disease and transfusion-associated graft-versus-host disease with red blood cell (RBC) transfusion.

STUDY DESIGN AND METHODS

A randomized, double-blind, controlled study was performed to assess the in vitro characteristics of amustaline-treated RBCs (test) compared with conventional (control) RBCs and to evaluate safety and efficacy of transfusion during and after cardiac surgery. The primary device efficacy endpoint was the postproduction hemoglobin (Hb) content of RBCs. Exploratory clinical outcomes included renal and hepatic failure, the 6-minute walk test (a surrogate for cardiopulmonary function), adverse events (AEs), and the immune response to amustaline-treated RBCs.

RESULTS

A total of 774 RBC unis were produced. Mean treatment difference in Hb content was -2.27 g/unit (95% confidence interval, -2.61 to -1.92 g/unit), within the prespecified equivalence margins (±5 g/unit) to declare noninferiority. Amustaline-treated RBCs met European guidelines for Hb content, hematocrit, and hemolysis. Fifty-one (25 test and 26 control) patients received study RBCs. There were no significant differences in RBC usage or other clinical outcomes. Observed AEs were within the spectrum expected for patients of similar age undergoing cardiovascular surgery requiring RBCs transfusion. No patients exhibited an immune response specific to amustaline-treated RBCs.

CONCLUSION

Amustaline-treated RBCs demonstrated equivalence to control RBCs for Hb content, have appropriate characteristics for transfusion, and were well tolerated when transfused in support of acute anemia. Renal impairment was characterized as a potential efficacy endpoint for pivotal studies of RBC transfusion in cardiac surgery.

Infectious Complications of Transfusion of Blood Components

Transfusions are lifesaving but are not without some risks. During the middle of the last century, infectious complications were common from transfusions. By the mid 1980s the risk of transfusion transmission of infections became much lower. With the advent of emerging diseases, however, infectious risks became more prominent for a period of time. Now we live in a time where death from transfusion transmission is 10%–15% of all transfusion-associated deaths and is the lowest in history. As the risks are identified and new screens or processes are put in place, the associated transfusion transmission of infection will continue to have reducing risks and blood supply will continue to be safer still.

Surface modification of platelet concentrate bags to reduce biofilm formation and transfusion sepsis

Bacterial contamination of blood products poses a major risk in transfusion medicine, including transfusions involving platelet products. Although testing systems are in place for routine screening of platelet units, the formation of bacterial biofilms in such units may decrease the likelihood that bacteria will be detected. This work determined the surface properties of p-PVC platelet concentrate bags and investigated how these characteristics influenced biofilm formation. Serratia marcescens and Staphylococcus epidermidis, two species commonly implicated in platelet contamination, were used to study biofilm growth. The platelet concentrate bags were physically flattened to determine if reducing the surface roughness altered biofilm formation. The results demonstrated that the flattening process of the platelet bags affected the chemistry of the surface and reduced the surface hydrophobicity. Flattening of the surfaces resulted in a reduction in biofilm formation for both species after 5 days, with S. marcescens demonstrating a greater reduction. However, there was no significant difference between the smooth and flat surfaces following 7 days' incubation for S. marcescens and no significant differences between any of the surfaces following 7 days' incubation for S. epidermidis. The results suggest that flattening the p-PVC surfaces may limit potential biofilm formation for the current duration of platelet storage time of 5 days. It is hoped that this work will enhance the understanding of how surface properties influence the development of microbial biofilms in platelet concentrate bags in order to devise a solution to discourage biofilm formation.

Enhancing blood donor skin disinfection using natural oils

BACKGROUND

Effective donor skin disinfection is essential in preventing bacterial contamination of blood components with skin flora bacteria like Staphylococcus epidermidis. Cell aggregates of S. epidermidis (biofilms) are found on the skin and are resistant to the commonly used donor skin disinfectants chlorhexidine-gluconate and isopropyl alcohol. It has been demonstrated that essential oils synergistically enhance the antibacterial activity of chlorhexidine-gluconate. The objective of this study was to test plant-extracted essential oils in combination with chlorhexidine-gluconate or chlorhexidine-gluconate plus isopropyl alcohol for their ability to eliminate S. epidermidis biofilms.

STUDY DESIGN AND METHODS

The composition of oils extracted from Artemisia herba-alba, Lavandula multifida, Origanum marjoram, Rosmarinus officinalis, and Thymus capitatus was analyzed using gas chromatography-mass spectrometry. A rabbit model was used to assess skin irritation caused by the oils. In addition, the anti-biofilm activity of the oils used alone or in combination with chlorhexidine-gluconate or chlorhexidine-gluconate plus isopropyl alcohol was tested against S. epidermidis biofilms.

RESULTS

Essential oil concentrations 10%, 20%, and 30% were chosen for anti-biofilm assays, because skin irritation was observed at concentrations greater than 30%. All oils except for O. marjoram had anti-biofilm activity at these three concentrations. L. multifida synergistically enhanced the anti-biofilm activity of chlorhexidine-gluconate and resulted in the highest anti-biofilm activity observed when combined with chlorhexidine-gluconate plus isopropyl alcohol. Gas chromatography-mass spectrometry revealed that the main component contributing to the activity of L. multifida oil was a natural terpene alcohol called linalool.

CONCLUSION

The anti-biofilm activity of chlorhexidine-gluconate plus isopropyl alcohol can be greatly enhanced by L. multifida oil or linalool. Therefore, these components could potentially be used to improve blood donor skin disinfection.

Noninvasive pH monitoring for bacterial detection in platelet concentrates

BACKGROUND

Bacterial contamination of platelet concentrates (PCs) remains the prevalent posttransfusion infectious risk. The pH SAFE system, a noninvasive method used to measure pH of PC for quality control, was evaluated herein as a rapid method to detect bacterial contamination in PCs.

STUDY DESIGN AND METHODS

Pairs of ABO-D-matched apheresis and buffy coat PCs were pooled and split into two pH SAFE platelet bags. One of the bags served as the control unit, while the other was inoculated with one of nine clinically relevant bacteria (target concentration approx. 1 colony-forming units [CFUs]/mL). The pH of both PCs was measured over 7 days of storage at approximately 4-hour intervals during daytime. One-milliliter samples were taken at the testing points to determine bacterial concentration.

RESULTS

PCs with pH values of less than 6.6 or with a pH change over time (ΔpH/Δtime) greater or equal than 0.046 pH units/hr are suspected of being contaminated. pH decreased significantly during storage in all bacterially inoculated PC at concentrations of more than 10(7) CFUs/mL (p < 0.0001). A significant decrease in pH (p < 0.0001) was noticed as early as 28 hours in units with Bacillus cereus and as late as 125 hours in units containing Staphylococcus epidermidis. Interestingly, PCs containing Gram-negative species showed a decline in pH followed by a rebound.

CONCLUSIONS

The pH SAFE system allows for repeated, noninvasive pH screening during PC storage. A significant decrease in pH could serve as an indicator of clinically significant levels of bacterial contamination. Since differences in pH decline were observed among bacterial species, continuous pH monitoring in PCs is recommended.

INVESTIGATION OF BIOFILM FORMATION IN COAGULASE-NEGATIVE STAPHYLOCOCCI ISOLATED FROM PLATELET CONCENTRATE BAGS

Platelet Concentrates (PCs) are the blood components with the highest rate of bacterial contamination, and coagulase-negative staphylococci (CoNS) are the most frequently isolated contaminants. This study investigated the biofilm formation of 16 contaminated units out of 691 PCs tested by phenotypic and genotypic methods. Adhesion in Borosilicate Tube (ABT) and Congo Red Agar (CRA) tests were used to assess the presence of biofilm. The presence of icaADC genes was assessed by means of the Polymerase Chain Reaction (PCR) technique. With Vitek(r)2, Staphylococcus haemolyticus was considered the most prevalent CoNS (31.25%). The CRA characterized 43.8% as probable biofilm producers, and for the ABT test, 37.5%. The icaADC genes were identified in seven samples by the PCR. The ABT technique showed 85.7% sensitivity and 100% specificity when compared to the reference method (PCR), and presented strong agreement (k = 0.8). This study shows that species identified as PCs contaminants are considered inhabitants of the normal skin flora and they might become important pathogens. The results also lead to the recommendation of ABT use in laboratory routine for detecting biofilm in CoNS contaminants of PCs.

Micro-concentration Lipopolysaccharide as a Novel Stimulator of Megakaryocytopoiesis that Synergizes with IL-6 for Platelet Production

Lipopolysaccharide (LPS) induces platelet activation and enhances platelet sensitivity to aggregation, which might alter platelet counts. We found that serial doses of micro-concentration LPS significantly increased the platelet count in mice treated with kanamycin, along with increased expression of IL-6 compared with IL-3 and TPO in megakaryocytes obtained from the mouse bone morrow following LPS administration. Furthermore, LPS at lower levels ranging plus IL-6 effectively stimulated CFU-MK formation and increased CD41 expression and megakaryocyte polyploidization. Meanwhile, there was a sustained rise in the percentage of reticulated platelets in the whole blood in response to low-dosage LPS combined with IL-6. In vivo experiments also demonstrated that the administration of LPS combined with IL-6 substantially enhanced the number of circulating platelets in normal and thrombocytopenic mice. Notably, the optimal LPS concentration in combination with IL-6 might be a novel stimulator of TLR4 and IL-6R expression in Dami cell lines, which initially occurs through TLR4-IL-6R crosstalk and then involves the activation of NF-κB and phosphorylation of p38 MAPK. These data suggest a new paradigm for the regulation of megakaryocytopoiesis and platelet production via a synergistic effect of LPS and IL-6, which has the potential to be used for the design of new therapies.

Platelet transfusion for patients with cancer

BACKGROUND

Platelet transfusion is a critical and often necessary aspect of managing cancer. Low platelet counts frequently lead to bleeding complications; however, the drugs used to combat malignancy commonly lead to decreased production and destruction of the very cell whose function is essential to stop bleeding. The transfusion of allogeneic platelet products helps to promote hemostasis, but alloimmunization may make it difficult to manage other complications associated with cancer.

METHODS

The literature relating to platelet transfusion in patients with cancer was reviewed.

RESULTS

Platelet storage, dosing, transfusion indications, and transfusion response are essential topics for health care professionals to understand because many patients with cancer will require platelet transfusions during the course of treatment. The workup and differentiation of non-immune-mediated compared with immune-mediated platelet refractoriness are vital because platelet management is different between types of refractoriness.

CONCLUSIONS

A combination of appropriate utilization of platelet inventory and laboratory testing coupled with communication between those caring for patients with cancer and those providing blood products is essential for effective patient care.

Addition of sialidase or p38 MAPK inhibitors does not ameliorate decrements in platelet in vitro storage properties caused by 4 °C storage

BACKGROUND AND OBJECTIVES

Bacterial proliferation is inhibited in platelets (PLTs) stored at refrigerated temperatures, but also dramatically decreases PLT in vivo survival. Recent studies have demonstrated that cold temperature (CT) stored PLTs secrete sialidases upon re-warming, removing sialic acid from the PLT surface, which may be responsible for clustering of GPIbα and PLT clearance from circulation. In this study, the influence of a sialidase inhibitor or a p38 MAP kinase inhibitor was evaluated in units stored at 4 °C.

MATERIALS AND METHODS

After collection of a single Trima apheresis unit (n = 12), PLTs were aliquoted into four 60-ml CLX storage bags. One bag was stored at 20-24 °C (RT) with continuous agitation; a second bag was stored at 4 °C without agitation; a third bag was held at 4 °C without agitation with sialidase inhibitor, a fourth bag was incubated at 4 °C with a p38 MAPK inhibitor without agitation.

RESULTS

Beginning from Day 1, all in vitro PLT parameters were adversely affected by CT compared to those of RT. Similar in vitro storage properties were observed in CT PLT in the presence or absence of sialidase or p38 MAPK inhibitors. P38 MAPK phosphorylation inhibition was not observed at CT. Decrease of sialidase activity was observed for 2 days in PLTs stored in additive solution but not in plasma.

CONCLUSION

Addition of either sialidase or p38 MAPK inhibitors do not improve any in vitro parameters of PLTs stored at 4 °C in 100% plasma.

Characterization of the growth dynamics and biofilm formation of Staphylococcus epidermidis strains isolated from contaminated platelet units

Bacterial contamination of platelet concentrates (PCs) poses the highest transfusion-associated infectious risk, with Staphylococcus epidermidis being a predominant contaminant. Herein, the growth dynamics of 20 S. epidermidis strains in PCs and regular media were characterized. Strains were categorized as fast (short lag phase) or slow (long lag phase) growers in PCs. All strains were evaluated for the presence of the biofilm-associated icaAD genes by PCR, their capability to produce extracellular polysaccharide (slime) on Congo red agar plates and their ability to form surface-attached aggregates (biofilms) in glucose-supplemented trypticase soy broth (TSBg) using a crystal violet staining assay. A subset of four strains (two slow growers and two fast growers) was further examined for the ability for biofilm formation in PCs. Two of these strains carried the icAD genes, formed slime and produced biofilms in TSBg and PCs, while the other two strains, which did not carry icaAD, did not produce slime or form biofilms in TSBg. Although the two ica-negative slime-negative strains did not form biofilms in media, they displayed a biofilm-positive phenotype in PCs. Although all four strains formed biofilms in PCs, the two slow growers formed significantly more biofilms than the fast growers. Furthermore, growth experiments of the two ica-positive strains in plasma-conditioned platelet bags containing TSBg revealed that a slow grower isolate was more likely to escape culture-based screening than a fast grower strain. Therefore, this study provides novel evidence that links S. epidermidis biofilm formation with slow growth in PCs and suggests that slow-growing biofilm-positive S. epidermidis would be more likely to be missed with automate culture.

Evaluation of a universal point-of-issue assay for bacterial detection in buffy coat platelet components

Bacterial contamination of platelet concentrates poses a major post-transfusion infectious risk. This study was aimed at evaluating the efficacy of the BacTx(®) assay (Immunetics Inc.) for bacterial detection in leucocyte-reduced buffy coat platelet pools and for its sensitivity in detecting clinical isolates, including bacteria that form surface-attached aggregates (biofilm positives). Platelet pools were inoculated at bacterial concentrations of 0·8-13 CFU/ml. The BacTx(®) assay detected all species at concentrations ≥10(3)  CFU/ml within 20-69 h of platelet incubation. Detection of slow-growing and biofilm-forming strains was delayed in comparison with the other strains. This assay could be used as a point-of-issue method to increase the safety of the platelet supply.

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.

A novel approach for rapid detection of bacterially contaminated platelet concentrates via sensitive measurement of microbial DNA polymerase activity

BACKGROUND

Transfusion of bacterially contaminated platelet concentrates (PCs) can result in serious health consequences for the affected patient. Before being released from blood banking facilities, PCs are routinely screened for bacterial contamination by culture-based tests. However, culture-based PC screening methods require extended holding and incubation periods and are prone to false-negative results due to sampling error. Screening PCs closer to the time of transfusion using rapid point-of-issue tests represents an alternative approach; however, FDA-approved assays generally suffer from a lack of sensitivity.

STUDY DESIGN AND METHODS

Presented herein is the feasibility of a novel approach toward rapid, sensitive, and universal detection of bacterially contaminated PCs via selective measurement of microbial DNA polymerase activity. This approach is achieved using a differential cell lysis procedure in combination with enzymatic template generation and amplification (termed ETGA-PC assay).

RESULTS

Serial dilution spiking experiments revealed an approximate sensitivity of 30 to 200 colony-forming units (CFUs)/mL (mean, 85 CFUs/mL) for Staphylococcus epidermidis, Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae. An additional 22 clinically relevant strains of bacteria were also detected below 200 CFUs/mL after spiking into PC aliquots. Furthermore, the ETGA-PC assay was able to accurately monitor the presence and growth of seven clinically relevant bacterial species that were spiked into PC units.

CONCLUSION

Together, the data presented here demonstrate that the ETGA-PC assay is a feasible approach for rapid and sensitive detection of bacterially contaminated PCs. Experiments, aimed at simplification and/or automation of the assay procedure, are under way.

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.

Biofilm formation by Staphylococcus capitis strains isolated from contaminated platelet concentrates

Bacterial contamination of platelet concentrates (PCs) poses the greatest infectious risk in modern transfusion medicine despite the implementation of measures such as improved skin disinfection and first aliquot diversion. The majority of PC contaminants are commensal skin flora introduced by venipuncture at the time of blood collection. The predominant organisms are Gram-positive coagulase-negative staphylococci such as Staphylococcus capitis. This bacterium has been implicated in numerous instances of infection and sepsis, likely for its ability to form surface-associated communities of micro-organisms encased in extracellular materials, known as biofilms. In the present study, five strains of S. capitis isolated from contaminated PCs were assessed for their ability to produce extracellular polysaccharide (slime), a canonical indicator of biofilm-formation ability, on Congo red agar plates. Biofilm formation was evaluated in both glucose-enriched trypticase soy broth (TSBg) and in PCs by using a crystal violet staining assay. The chemical nature of the biofilms was evaluated by disruption assays using sodium metaperiodate and proteinase K. In addition, biofilm architecture was observed by scanning electron microscopy. The presence of the biofilm-associated icaR and icaADBC genes was also examined by PCR. While only two out of the five S. capitis strains formed biofilms in TSBg, all strains formed biofilms in PCs. The ability of strains to produce extracellular polysaccharide and their possession of wild-type ica genes were not exclusive predictors of biofilm formation in TSBg or PCs; different profiles of biofilm markers were observed among isolates. This is likely due to the proteinaceous composition of the S. capitis biofilm matrix. Interestingly, an ica-negative, non-slime-producing isolate was capable of biofilm formation in PCs. Together, these data indicate that the platelet storage environment stimulates biofilm formation in S. capitis in the absence of extracellular polysaccharide production and that multiple bacterial factors and regulatory elements are likely involved in biofilm formation in this milieu.

Enhanced pathogenicity of biofilm-negative Staphylococcus epidermidis isolated from platelet preparations

BACKGROUND

The platelet (PLT) storage environment triggers the formation of surface-attached aggregates known as biofilms by the common PLT contaminant Staphylococcus epidermidis. The biofilm matrix is largely composed of polysaccharide intercellular adhesin (PIA) mediated by the icaADBC operon. However, PIA-negative S. epidermidis has been reported to form biofilms in PLT concentrates (PCs). Since biofilm formation is associated with increased virulence, this study was aimed at determining if PIA-negative S. epidermidis grown in PCs presents enhanced virulence using the nematode Caenorhabditis elegans as a host model for bacterial pathogenesis.

STUDY DESIGN AND METHODS

Biofilm-positive S. epidermidis ATCC 35984 and 9142, which carry the icaADBC operon, and biofilm-negative S. epidermidis ATCC 12228 and 9142 ΔicaA were grown in regular media and in PCs and biofilm formation was quantified using a crystal violet assay. The virulence of these strains after passage through PCs was tested using nematode killing assays. Nematode survival was calculated using the Kaplan-Meier method and statistical differences were determined by log-rank analysis.

RESULTS

All S. epidermidis strains were able to form biofilms in PCs. Although persistence of a biofilm-positive phenotype in the biofilm-negative strains grown in PCs was not observed after passage in regular medium, the virulence of all strains was significantly increased as demonstrated by shortened life spans of the nematodes in C. elegans killing assays.

CONCLUSION

Our findings highlight the potential of an increased risk of nosocomial infections caused by S. epidermidis in transfusion recipients since PC storage conditions promote biofilm formation, and possibly pathogenicity, of strains traditionally known to be attenuated for virulence.

Preserved functional and biochemical characteristics of platelet components prepared with amotosalen and ultraviolet A for pathogen inactivation

BACKGROUND

Platelet concentrate (PC) functionality decreases during storage. This is referred to as the storage lesion. Pathogen inactivation may accelerate or induce lesions, potentially accounting for reduced viability. Our aim was to characterize functional and biochemical properties of platelets (PLTs) from photochemically treated buffy-coat PCs (PCT-PCs) compared to those from conventional PCs.

STUDY DESIGN AND METHODS

Four PCT-PCs and four conventional PCs were stored for 6.5 days and PLT function and proteomic profiles were examined at various time points during storage. To evaluate their intrinsic properties, samples of stored PLTs were taken, washed, and suspended in Tyrode's buffer before testing.

RESULTS

PLT counts and morphology were conserved although a slight increase in the PLT volume was observed after PCT. Glycoprotein (GP) IIbIIIa, IaIIa, and VI expression remained stable while GPIbα declined similarly in both types of PCs. A steep decrease (50%) in GPV occurred on Day 1.5 in PCT-PCs and Day 2.5 in control PCs. For both PCT- and control PCs, P-selectin expression and activated GPIIbIIIa remained low during storage. PCT- and control PCs were fully responsive to aggregation agonists up to Day 4.5 and exhibited similar perfusion functionality. Mitochondrial membrane potential and annexin A5 binding of PCT-PCs and control PCs were comparable. Two-dimensional differential in-gel electrophoresis and mass spectrometry profiles for 1882 protein spots revealed only three proteins selectively changed in PCT-PCs compared to control-PCs.

CONCLUSION

Washed treated and untreated PCs have similar functional, morphologic, and proteomic characteristics provided that PLTs are suspended in an appropriate medium during testing.