Pathogen displacement during intermittent catheter insertion: a novel in vitro urethra model.

AIM: To develop a novel in vitro urethra model and use it to determine if insertion of an intermittent urinary catheter (IC) displaces pathogenic bacteria from the urethral meatus along the urethra. METHODS: Displacement of microbial growth after catheter insertion was assessed using a novel in vitro urethra model. The in vitro urethra model utilized chromogenic agar and was inoculated with bacteria at one side of the artificial urethra channel, to act as a contaminated urethral meatus, before an IC was inserted into the channel. Three ICs types were used to validate the in vitro urethra model and methodology. RESULTS: When compared to the bacterial growth control, a significant difference in bacterial growth was found after insertion of the uncoated (P ≤ 0·001) and hydrophilic coated (P ≤ 0·009) catheters; no significant difference when a prototype catheter was inserted into the in vitro urethra model with either bacterial species tested (P ≥ 0·423). CONCLUSION: The results presented support the hypothesis that a single catheter insertion can initiate a catheter-associated urinary tract infection. SIGNIFICANCE AND IMPACT OF THE STUDY: The in vitro urethra model and associated methodology were found to be reliable and reproducible (P ≥ 0·265) providing new research tool for the development and validation of emerging technologies in urological healthcare.

Donor deferral policies for men who have sex with men: past, present and future.

We review the history and evolution of blood donor criteria for men who have sex with men (MSM). Deferral policies in many jurisdictions, including Australia, New Zealand, Canada, the United States, Brazil and many western European countries are based on a period of abstinence from MSM, often of 12 months duration. Several countries (Italy, Spain and Portugal) defer donors based on sexual behaviours considered to be at high risk, regardless of whether the partner is same sex or opposite sex. Compliance is a key determinant in the efficacy of any deferral policy. We summarize research themes and strategies discussed at a January 2017 meeting held in Toronto, Canada, to provide an evidence basis for future policy changes.

Raman spectroscopy of stored red blood cell concentrate within sealed transfusion blood bags.

The standard practice in blood banks worldwide involves storage of red blood cells (RBCs) in plastic bags until they are needed for transfusion. During storage, the cells gradually degrade in functionality, a condition described as RBC storage lesion. Standard analytical techniques cannot assess the blood quality without breaching the sterility of the transfusion bag. In this study, we employed a commercially available spatially offset Raman spectroscopy (SORS) system using a custom designed protocol to non-invasively explore the biochemical changes in RBC concentrate of healthy donors over a storage period of approximately 42 days in standard transfusion bags, under standard storage conditions. The results reveal an increase in the oxygenation state of haemoglobin over the storage period for all donors, but different profiles for each donor. This study demonstrates the feasibility of acquiring consistent biochemical information relevant to the quality of stored blood, in situ through sealed blood transfusion bags using a commercially available instrument.

The role of neurotensin in vulnerability for self-injurious behaviour: studies in a rodent model.

BACKGROUND: Self-injurious behaviour is a debilitating characteristic that is commonly expressed in people with autism and other neurodevelopmental disorders, but the neurobiological basis of this maladaptive behaviour is not understood. Abnormal dopaminergic and glutamatergic neurotransmission has been implicated, especially in relation to basal ganglia and mesocorticolimbic circuits. As neurotensin is an important modulator of dopamine and glutamate in these circuits, we investigated its potential role in vulnerability for self-injury, using the pemoline model in rats. METHODS: Male Long-Evans rats were injected once daily with the psychostimulant pemoline or peanut oil vehicle on each of five consecutive days. Self-injury was quantified by measuring the area of injuries for each rat on each day of the experiment. Each brain was harvested on the sixth day, and the striatum and ventral tegmentum were dissected. Neurotensin-like immunoreactivity was quantified by radioimmunoassay from the dissected brain regions of some of the rats. Membrane and intracellular neurotensin receptor NTS1 were assayed from the striata of the remaining pemoline-treated or vehicle-treated rats by Western blot. In an additional experiment, male Long-Evans rats were treated with daily injections of vehicle or pemoline, and the NTS1 neurotensin receptor agonist PD149163 or the NTS1 receptor antagonist SR48692 (or respective vehicle solutions) was co-administered twice daily throughout the pemoline treatment regimen. The areas of injured tissue were measured, and the duration of self-injurious oral contact was quantified by video-recorded time samples throughout each day. RESULTS: Striatal neurotensin immunoreactivity was found to be significantly higher in pemoline-treated than in vehicle-treated rats. Moreover, both membrane-bound and intracellular levels of NTS1 receptor were significantly higher in the striata of pemoline-treated rats than in the striata of the vehicle-treated controls. When the NTS1 receptor agonist PD149163 was co-administered during the pemoline treatment regimen, it prolonged the daily durations of self-injurious oral contact and increased the severity of the injuries in the self-injurious rats. Conversely, co-administration of the NTS1 receptor antagonist SR48692 diminished the daily durations of self-injurious oral contact and decreased the severity of the injuries. CONCLUSIONS: The elevation of striatal neurotensin immunoreactivity during pemoline treatment, coupled with the effects of the NTS1 agonist and antagonist, suggests that neurotensin transmission in the striatum may be an important modulator of self-injurious behaviour in the pemoline model. Overall, the convergence of the behavioural and biochemical findings suggests that neurotensin signalling could be an important target for pharmacotherapeutic interventions for self-injurious behaviour.

Alternatives in blood operations when choosing non-DEHP bags.

The use of di-ethylhexyl-phthalate (DEHP) in blood bags is under discussion due to toxicity concerns and possible restrictions. A questionnaire among 15 blood centres in nine countries showed that none so far have fully switched to non-DEHP blood bags. If centres had to change, sites with a 42-day outdate would choose for a shorter outdating period, while others would allow a higher haemolysis rate (but within current specifications). To improve red cell quality, about half of the centres are willing to move to an alternative red cell storage solution, while the other half would not change for various reasons.

Early γ-irradiation and subsequent storage of red cells in SAG-M additive solution potentiate energy imbalance, microvesiculation and susceptibility to stress-induced apoptotic cell death.

γ-Irradiation of red blood cell (RBC) concentrates prevents transfusion-associated graft-versus-host disease but may diminish RBC quality. Herein, we show that early γ-irradiation (25 Gy) of RBC units and their subsequent storage in SAG-M additive solution altered membrane microvesiculation, supernatant haemoglobin and cytosolic ATP. γ-Irradiation did not influence phosphatidylserine externalization, a marker of erythrocyte apoptotic cell death (eryptosis), in RBC stored for 42 days. However, shorter periods (4-21 days) of storage accentuated eryptosis in γ-irradiated RBC versus untreated RBCs following energy depletion, suggesting that γ-irradiated RBC is primed for stress-induced eryptosis during storage.

Experiences with semi-routine production of riboflavin and UV-B pathogen-inactivated platelet concentrates in three blood centres.

BACKGROUND: For a clinical platelet (PLT) transfusion trial conducted in three countries, the production of PLT concentrates (PCs) that were pathogen inactivated with the Mirasol technology was set up and validated. While the Mirasol procedure is applied to an established PLT product, the PLT processing procedure still had to be modified to ensure a treated PC was of sufficient quality. Further, the effect of simulated transport conditions and the effect of ambient light on Mirasol-treated PCs was determined. STUDY DESIGN AND METHODS: Platelet concentrates in plasma were made from pooled buffy coats followed by Mirasol treatment. To mimic transport conditions, units were left unagitated for 6 h at room temperature. To mimic ambient light exposure, units were held unagitated for 4 h in direct fluorescent tube light. RESULTS: Measures had to be taken to allow 7-day storage of treated concentrates. In one site, PCs made from five buffy coats with >450 × 109 PLTs were removed from inventory. Another site went from five to four buffy coats per pool. Interruption of agitation for 6 h on day 3 did not induce meaningful changes in in vitro measures, even when stored up to 7 days. Exposure to ambient light for 4 h, either on day 3 or 6, had no effect on in vitro measures. CONCLUSION: The Mirasol pathogen inactivation process can be implemented in routine, but changes to current PLT processing methods might be needed. Transport conditions and 4-h-long ambient light exposure have no negative effect on the in vitro quality of Mirasol-treated PCs.

An investigation of red blood cell concentrate quality during storage in paediatric-sized polyvinylchloride bags plasticized with alternatives to di-2-ethylhexyl phthalate (DEHP).

BACKGROUND AND OBJECTIVES: Di-2-ethylhexyl phthalate (DEHP) is a blood bag plasticizer. It is also a toxin, raising concerns for vulnerable populations, for example, neonates and infants. Here, the in vitro quality of red cell concentrates (RCC) stored in paediatric bags formulated with alternative plasticizers to DEHP was compared. MATERIALS AND METHODS: RCC were pooled and split into polyvinylchloride (PVC)/DEHP, PVC/1,2-cyclohexanedicarboxylic acid diisononyl ester (DINCH) or PVC/butyryl trihexyl citrate (BTHC) bags. Quality was assessed on storage days 5, 21, 35 and 43. RESULTS: Metabolism differed among the bags: pCO2 levels were lowest and pO2 were highest in BTHC bags. Glucose consumption and lactate production suggested higher metabolic rates in BTHC bags. ATP levels were best maintained in DINCH bags (day 43 mean level: 2·86 ± 0·29 µmol/g Hb). RCC in BTHC bags had the greatest potassium release (54·6 ± 3·0 mm on day 43). From day 21, haemolysis was higher in BTHC bags (P < 0·01) and by day 43 had exceeded 0·8% (0·85 ± 0·10%). RCC in BTHC bags showed more microparticle formation than RCC in DEHP or DINCH bags. CONCLUSION: The results suggest that the BTHC formulation used was detrimental to RBC quality. DINCH bags could be a viable alternative to DEHP: they outperformed DEHP bags energetically, with better maintenance of ATP levels.

Non-invasive spectroscopy of transfusable red blood cells stored inside sealed plastic blood-bags.

After being separated from (donated) whole blood, red blood cells are suspended in specially formulated additive solutions and stored (at 4 °C) in polyvinyl chloride (PVC) blood-bags until they are needed for transfusion. With time, the prepared red cell concentrate (RCC) is known to undergo biochemical changes that lower effectiveness of the transfusion, and thus regulations are in place that limit the storage period to 42 days. At present, RCC is not subjected to analytical testing prior to transfusion. In this study, we use Spatially Offset Raman Spectroscopy (SORS) to probe, non-invasively, the biochemistry of RCC inside sealed blood-bags. The retrieved spectra compare well with conventional Raman spectra (of sampled aliquots) and are dominated by features associated with hemoglobin. In addition to the analytical demonstration that SORS can be used to retrieve RCC spectra from standard clinical blood-bags without breaking the sterility of the system, the data reveal interesting detail about the oxygenation-state of the stored cells themselves, namely that some blood-bags unexpectedly contain measurable amounts of deoxygenated hemoglobin after weeks of storage. The demonstration that chemical information can be obtained non-invasively using spectroscopy will enable new studies of RCC degeneration, and points the way to a Raman-based instrument for quality-control in a blood-bank or hospital setting.

Healing pattern of reamed bone following bone harvesting by a RIA device.

Intramedullary nailing has been used for decades to treat fractures of the long bones. However, complications related to the increase in medullary pressure culminated in the development of the Reamer Irrigator Aspirator (RIA). Since its first clinical use, the RIA has moved from a reaming device to a cell and autologous bone-harvesting tool. This increase in use brings with it further clinical questions; namely, does the endosteal bone regenerate sufficiently to allow subsequent reaming procedures. In the current study, endosteal bone regeneration post reaming was assessed in an ovine model. The study included six animals that had one tibia reamed, while the contralateral tibia acted as an intact control. Animals were administered fluorochrome labels in vivo, and bone regeneration was assessed using radiographical analysis. The endpoint of the study was 12 weeks post-surgery, at which time ex vivo analysis consisted of computed tomography and histological assessments. In vivo radiographs indicated limited healing of the reamed bone. However, ex vivo computer tomographical analysis indicated no significant differences in terms of bone volume between the reamed bone and the intact bone. Histological assessment of these regions indicated new bone formation. Fluorescent labelling indicates strong bone formation from 9 weeks post-surgery and as such, the bone formed at 12 weeks was immature in nature and was actively undergoing remodelling. These results indicate that bone regeneration post-reaming was continuing at three months. Therefore, given more time it may have sufficiently healed to allow a surgeon to use the intramedullary canal for a re-reaming procedure.

A clinical governance framework for blood services.

BACKGROUND AND OBJECTIVES: The elements of clinical governance, which ensure excellence in clinical care, can be applied to blood services. In this survey, their application in a range of blood providers was gauged, with the aim of identifying best practice and producing a generalizable framework. MATERIALS AND METHODS: The Medical Directors of members of the Alliance of Blood Operators surveyed how different elements of clinical governance operated within their organizations and developed recommendations applicable in the blood service environment. RESULTS: The recommendations that emerged highlighted the importance of an organization's culture, with the delivery of optimal clinical governance being a corporate responsibility. Senior management must agree and promote a set of values to ensure that the system operates with the patient and donor at its heart. All staff should understand how their role fits into the 'journey to the patient', and a culture of openness promoted. Thus, reporting of errors and risks should be actively sought and praised, with penalties applied for concealment. Systems should exist to collect, analyse and escalate clinical outcomes, safety data, clinical risk assessments, incident reports and complaints to inform organizational learning. CONCLUSION: Clinical governance principles from general health care can be applied within blood services to complement good manufacturing practice. This requires leadership, accountability, an open culture and a drive for continuous improvement and excellence in clinical care.

The effect of processing method on the in vitro characteristics of red blood cell products.

BACKGROUND AND OBJECTIVES: While the clinical impact of differences in red blood cell (RBC) component processing methods is unknown, there are concerns they may be confounding variables in studies such as the ongoing 'age of blood' investigations. Here, we compare the in vitro characteristics of red cell concentrates (RCCs) produced by several different processing methods. MATERIALS AND METHODS: Nine processing methods were examined: three apheresis methods (Alyx, MCS+ and Trima), as well as leucoreduced whole blood-derived RCCs produced by buffy coat and whole blood filtration and non-leucoreduced RCCs. RCCs were stored in saline-adenine-glucose-mannitol or additive solutions (AS) 1 or 3 for 42 days, with quality tested on day 5 and day 42. RESULTS: Many significant product differences were observed both early in and at the end of storage. Mean haemoglobin (Hb) ranged from 52 to 71 g/unit and mean Hct from 59·5 to 64·8%. Most RCC passed regulated quality control criteria according to Canadian Standards Association guidelines, although there were some failures relating to Hb content and residual WBC counts. CONCLUSION: Processing method impacts RCC characteristics throughout storage; better understanding of these differences and reporting of processing method details is critical.

The role of the insulin­like growth factor (IGF) axis in osteogenic and odontogenic differentiation.

The insulin-like growth factor (IGF) axis is a multicomponent molecular network which has important biological functions in the development and maintenance of differentiated tissue function(s). One of the most important functions of the IGF axis is the control of skeletal tissue metabolism by the finely tuned regulation of the process of osteogenesis. To achieve this, the IGF axis controls the activity of several cell types­osteoprogenitor cells, osteoblasts, osteocytes and osteoclasts to achieve the co-ordinated development of appropriate hard tissue structure and associated matrix deposition. In addition, there is an increasing awareness that the IGF axis also plays a role in the process of odontogenesis (tooth formation). In this review, we highlight some of the key findings in both of these areas. A further understanding of the role of the IGF axis in hard tissue biology may contribute to tissue regeneration strategies in cases of skeletal tissue trauma.

Counting platelets at transfusion threshold levels: impact on the decision to transfuse. A BEST Collaborative - UK NEQAS(H) International Exercise.

BACKGROUND AND OBJECTIVES: Obtaining accurate and precise platelet enumeration in automatic platelet analysers at low platelet counts is a challenge. To explore the performance of current haematology analysers in counting platelet concentrations usually used as platelet transfusion threshold. MATERIAL AND METHODS: An international exercise where four blood samples with platelet levels near usual platelet transfusion thresholds was prepared and distributed. RESULTS: The samples shipped had a platelet count of 6·3, 13·3, 21·6 and 53·0 × 10(9) /l according to the international reference method. We received 82 sets of results from nine countries. Instruments from six different manufacturers were represented. Although the mean count for each of the four samples was very similar to the values, according to the reference method (9·0, 16·2, 23·0 and 57·6 × 10(9) /l), significant variability in the results was found. Assuming that these were patient samples and the result of the count used to indicate a prophylactic platelet transfusion, undertransfusion would have occurred for 24·5% of the LP1 samples at a transfusion threshold of 10 × 10(9) /l and, at a threshold of 20 × 10(9) /l, undertransfusion would have occurred for 7·2% of the LP1 and 16·2% of the LP2 samples and overtransfusion would have occurred with 23·1% of the LP3 samples. CONCLUSION: The results suggest that significant inaccuracy exists in counting low levels of platelets and that this inaccuracy might have a significant impact in under- and overtransfusion of platelet concentrates to patients.

The effect of timing of gamma-irradiation on hemolysis and potassium release in leukoreduced red cell concentrates stored in SAGM.

While irradiation of red cell concentrates (RCC) prevents graft-versus-host disease in susceptible transfusion recipients, it also damages red blood cells (RBC). To understand the ability of irradiation regulations to prevent transfusion of inferior units, we irradiated 980 RCC in saline-adenine-glucose-mannitol (SAGM) using various combinations of pre-irradiation age and post-irradiation storage times, and measured hemolysis and extracellular potassium levels. We observed unacceptably high hemolysis (>0·8%) in some RCC and elevated extracellular potassium levels in all gamma-irradiated RCC. This suggests that more restrictive storage times should be considered for RCC in SAGM.

Manipulating the diseased oral microbiome: the power of probiotics and prebiotics.

Dental caries and periodontal disease are amongst the most prevalent global disorders. Their aetiology is rooted in microbial activity within the oral cavity, through the generation of detrimental metabolites and the instigation of potentially adverse host immune responses. Due to the increasing threat of antimicrobial resistance, alternative approaches to readdress the balance are necessary. Advances in sequencing technologies have established relationships between disease and oral dysbiosis, and commercial enterprises seek to identify probiotic and prebiotic formulations to tackle preventable oral disorders through colonisation with, or promotion of, beneficial microbes. It is the metabolic characteristics and immunomodulatory capabilities of resident species which underlie health status. Research emphasis on the metabolic environment of the oral cavity has elucidated relationships between commensal and pathogenic organisms, for example, the sequential metabolism of fermentable carbohydrates deemed central to acid production in cariogenicity. Therefore, a focus on the preservation of an ecological homeostasis in the oral environment may be the most appropriate approach to health conservation. In this review we discuss an ecological approach to the maintenance of a healthy oral environment and debate the potential use of probiotic and prebiotic supplementation, specifically targeted at sustaining oral niches to preserve the delicately balanced microbiome.

The balance of oral homeostasis requires delicate adjustments to prevent and counteract disease.The metabolic activities of the complete microbiome, not only key pathogens or commensals, are important to the maintenance of health.Metabolomics techniques can be valuable in identifying environmental niches deficient in disease that can act as targets for probiotic and prebiotic treatments.

Standardization of CD62P measurement: results of an international comparative study.

BACKGROUND AND OBJECTIVES: Despite long being a mainstay in describing platelet activation via degranulation, interlaboratory variation remains an issue in measurement of membrane CD62P by flow cytometry. Our objective was to identify actions that may minimize this variation. MATERIALS AND METHODS: Sixteen laboratories participated in an international comparative study. Two sets of platelet samples were prepared in one laboratory. Set 1 was stained and fixed; set 2 was fixed and required staining at participating laboratories. A single-staining method was used, and platelet populations were selected based on forward scatter/side scatter characteristics. Calibration beads were used to standardize measurement across different instruments. RESULTS: There was a large discrepancy in reported CD62P values among study sites [interlaboratory coefficient of variance (CV): 36-78%]. When electronic data were re-analysed by a single analyst using a consistent gating strategy and a stable reference point, variation decreased markedly (CV < 12%), indicating a problem with isotype control samples, possibly related to sample fixation or shipment. CONCLUSION: Consensus regarding gating strategies and use of a reliable reference point would greatly improve agreement in interlaboratory CD62P measurement.

Increased Handpiece Speeds without Air Coolant: Aerosols and Thermal Impact.

This study assessed the impact of increased speed of high-speed contra-angle handpieces (HSCAHs) on the aerosolization of a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) surrogate virus and any concomitant thermal impact on dental pulp. A bacteriophage phantom-head model was used for bioaerosol detection. Crown preparations were performed with an NSK Z95L Contra-Angle 1:5 (HSCAH-A) and a Bien Air Contra-Angle 1:5 Nova Micro Series (HSCAH-B) at speeds of 60,000, 100,000, and 200,000 revolutions per minute (rpm), with no air coolant. Bioaerosol dispersal was measured with Φ6-bacteriophage settle plates, air sampling, and particle counters. Heating of the internal walls of the pulp chambers during crown preparation was assessed with an infrared camera with HSCAH-A and HSCAH-B at 200,000 rpm (water flows ≈15 mL min-1 and ≈30 mL min-1) and an air-turbine control (≈23.5 mL min-1) and correlated with remaining tissue thickness measurements. Minimal bacteriophage was detected on settle or air samples with no notable differences observed between handpieces or speeds (P > 0.05). At all speeds, maximum settled aerosol and average air detection was 1.00 plaque-forming units (pfu) and 0.08 pfu/m3, respectively. Irrespective of water flow rate or handpiece, both maximum temperature (41.5°C) and temperature difference (5.5°C) thresholds for pulpal health were exceeded more frequently with reduced tissue thickness. Moderate and strong negative correlations were observed based on Pearson's correlation coefficient, between remaining dentine thickness and either differential (r = -0.588) or maximum temperature (r = -0.629) measurements, respectively. Overall, HSCAH-B generated more thermal energy and exceeded more temperature thresholds compared to HSCAH-A. HSCAHs without air coolant operating at speeds of 200,000 rpm did not increase bioaerosolization in the dental surgery. Thermal risk is variable, dependent on handpiece design and remaining dentine thickness.

Application of the ADVIA cerebrospinal fluid assay to count residual red blood cells in blood components.

BACKGROUND AND OBJECTIVES: There is no automated, accurate assay for the enumeration of residual red blood cells (rRBCs) in non-RBC components for transfusion, despite the potential risk of allo-immunization when mismatched components are transfused. MATERIALS AND METHODS: The automated ADVIA 120 cerebrospinal fluid (CSF) assay, which is approved to count RBCs and WBCs in CSF samples, was optimized and tested to measure rRBC in platelet concentrate (PC) and plasma components. RESULTS: Sample dilution, incubation time and reagent volume were optimized for use with non-RBC blood products. The assay was linear (R(2) = 0·99), even at low rRBCs counts. Intra- and inter-assay variation gave coefficients of variance (CV) between 2·2 and 9·4% and 2·6 and 14·9%, respectively, depending on rRBC levels. Good correlation (r = 0·995) was found between the automated assay and manual counting, which is considered the gold standard. Using the automated assay, the range of rRBCs (count/unit) in buffy-coat platelet concentrate (PCs) was 27-5505 × 10(6) and in apheresis PCs was 1-361 × 10(6). CONCLUSION: The ADVIA CSF assay is a sensitive, precise and accurate means to assess rRBC counts in non-RBC 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.