Residual risk of bacterial contamination of platelets: six years of experience with sterility testing

Comparative genomics analysis of six Cutibacterium acnes strains isolated from contaminated platelet concentrates

Cutibacterium acnes is a bacterial skin commensal that is often isolated during routine testing of blood products like platelet concentrates (PCs). Due to the slow-growing nature of this bacterium in culture media, C. acnes contaminated PCs are often transfused into vulnerable patients before retrieval of these units can be initiated. This study aimed at obtaining the whole-genome sequence of six C. acnes isolates derived from contaminated PCs, comparing and assessing their genetic backgrounds. Furthermore, the whole genomes of the PC isolates were compared to clinical isolates obtained from different sites and types of infection. The results indicate that these PC isolates assessed belong to four phylotypes, namely IA, IB, II and III. Whole-genome comparisons identified differences in the virulence profiles of the isolates and provide a foundation for future studies aimed at evaluating the risk to transfusion patients by determining whether the expression of virulence factors is impacted in the PC storage environment.

Comparative evaluation of hematological parameters and instrument performance in single and double plateletpheresis procedures using Haemonetics MCS+ and Trima Accel systems

OBJECTIVES

Plateletpheresis (PP) has become increasingly prevalent due to its cost-effectiveness and fewer immunological and infectious complications for recipients. This study compares hematological indices of platelet donors and instrument-related parameters in high-yield PP donors using Haemonetics MCS+ and Trima Accel.

METHODS

Eligible and healthy PP donors meeting the platelet donation criteria were randomly selected.19 single-dose platelet (SDP), and 26 double-dose platelet (DDP) donors underwent PP using the Haemonetics MCS+, while 21 SDP and 21 DDP donors were processed using the Trima Accel system. Complete Blood Count (CBC) and hematological indices of donors between groups with both devices were measured with the cell counter. Platelet yield, collection efficiency (CE), and collection rate (CR) were evaluated for both devices. Results were reported using R-4.3.2 software and a p-value <0.05 was considered statistically significant.

RESULTS

The Trima Accel processed significantly more blood volume and had shorter procedure times than MCS+. Platelet yield in the SDP group with Trima Accel was significantly higher than the Haemonetics MCS+. The Trima Accel demonstrated a significantly higher CR and CE than the MCS+ in both SDP and DDP groups. Post-PP lymphocyte counts significantly decreased with the Trima compared to the MCS+ in the SDP group. However, post-PP hematocrit (HCT), mean corpuscular volume (MCV), and mean platelet volume (MPV) in the DDP group with the MCS+ were significantly lower than Trima.

CONCLUSION

Double-dose plateletpheresis (DDP) offers advantages in cost-effectiveness and platelet production, and although it reduces some hematological indices, these remain within normal limits. The Trima Accel may offer superior efficiency and processing times compared to the MCS+. However, careful monitoring of DDP donors following AABB standards remains essential.

Modulation of Staphylococcus aureus gene expression during proliferation in platelet concentrates with focus on virulence and platelet functionality

Staphylococcus aureus is a well-documented bacterial contaminant in platelet concentrates (PCs), a blood component used to treat patients with platelet deficiencies. This bacterium can evade routine PC culture screening and cause septic transfusion reactions. Here, we investigated the gene expression modulation within the PC niche versus trypticase soy media (TSB) of S. aureus CBS2016-05, a strain isolated from a septic reaction, in comparison to PS/BAC/317/16/W, a strain identified during PC screening. RNA-seq analysis revealed upregulation of the capsule biosynthesis operon (capA-H), surface adhesion factors (sasADF), clumping factor A (clfA), protein A (spa), and anaerobic metabolism genes (pflAB, nrdDG) in CBS2016-05 when grown in PCs versus TSB, implying its enhanced pathogenicity in this milieu, in contrast to the PS/BAC/317/16/W strain. Furthermore, we investigated the impact of S. aureus CBS2016-05 on platelet functionality in spiked PCs versus non-spiked PC units. Flow cytometry analyses revealed a significant decrease in glycoprotein (GP) IIb (CD41) and GPIbα (CD42b) expression, alongside increased P-selectin (CD62P) and phosphatidylserine (annexin V) expression in spiked PCs compared to non-spiked PCs (p = 0.01). Moreover, spiked PCs exhibited a drastic reduction in MitoTrack Red FM and Calcein AM positive platelets (87.3% vs. 29.4%, p = 0.0001 and 95.4% vs. 24.7%, p = 0.0001) in a bacterial cell density manner. These results indicated that S. aureus CBS2016-05 triggers platelet activation and apoptosis, and compromises mitochondrial functionality and platelet viability, in contaminated PCs. Furthermore, this study enhanced our understanding of the effects of platelet-bacteria interactions in the unique PC niche, highlighting S. aureus increased pathogenicity and deleterious effect on platelet functionality in a strain specific manner. Our novel insights serve as a platform to improve PC transfusion safety.

Temporal dynamics of in vitro hemostatic function in platelets cryopreserved using a novel approach for rapid issuance

BACKGROUND

Current procedures for thawing and issuing of cryopreserved platelets (CPPs) are laborious and have remained challenging in emergency settings such as blood banks and military operations. In this prospective study, a novel processing method designed to facilitate the rapid issuance of CPPs with no postthaw handling required was developed and functionally characterized in parallel with standard CPPs manufactured.

STUDY DESIGN AND METHODS

Double-dose plateletpheresis units (n = 42) were cryopreserved at -80°C in 5%-6% dimethyl sulfoxide to produce matched pairs thawed successively over a 27-month period for comparison between two processing arms. In contrast to the standard CPPs manufactured as standalone units, platelets were frozen in tandem with resuspending plasma in a distinct partition as a single unit in the novel method, herein referred to as tandem CPPs. Postthaw (PT) CPPs from both arms were assessed at PT0-, 12-, and 24-h to measure platelet recovery, R-time (time to clot initiation; min), and maximum amplitude (MA; clot strength; mm) using thromboelastography.

RESULTS

In the overall dataset, mean platelet recovery was higher (p < .0005) for tandem CPPs (83.9%) compared with standard CPPs (73.3%) at PT0; mean R-times were faster (p < .0005) for tandem CPPs (2.5-3.6 min) compared with standard CPPs (3.0-3.8 min); mean MA was higher for tandem CPPs (57.8-59.5 mm) compared with standard CPPs (52.1-55.8 mm) at each postthaw time point (p < .05).

CONCLUSION

Robust temporal dynamics of superior hemostatic functionality were established for tandem CPPs over extended cryopreservation up to 27 months and 24 h of postthaw storage.

Characterization of transfusion-relevant bacteria reference strains in a lyophilized format

BACKGROUND AND OBJECTIVES

Blood safety measures used by blood establishments to increase blood component safety can be validated using Transfusion-Relevant Bacterial Reference Strains (TRBRS). Ultra-cold storage conditions and manual preparation of the current TRBRS may restrict their practical use. To address this issue, the ISBT Transfusion-Transmitted Infectious Diseases Working Party's Bacterial Subgroup organized an international study to validate TRBRS in a user-friendly, lyophilised format.

MATERIALS AND METHODS

Two bacterial strains Klebsiella pneumoniae PEI-B-P-08 and Staphylococcus aureus PEI-B-P-63 were manufactured as lyophilised material. The lyophilised bacteria were distributed to 11 different labs worldwide to assess the robustness for enumeration, identification and determination of growth kinetics in platelet concentrates (PCs).

RESULTS

Production of lyophilised TRBRS had no impact on the growth properties compared with the traditional format. The new format allows a direct low-quantity spiking of approximately 30 bacteria in PCs for transfusion-relevant experiments. In addition, the lyophilised bacteria exhibit long-term stability across a broad temperature range and can even be directly rehydrated in PCs without losing viability. Interlaboratory comparative study demonstrated the robustness of the new format as 100% of spiked PC exhibited growth.

CONCLUSION

Lyophilised TRBRS provide a user-friendly material for transfusion-related studies. TRBRS in the new format have improved features that may lead to a more frequent use in the quality control of transfusion-related safety measures in the future.

Evaluation of bacterial safety approaches of platelet blood concentrates: bacterial screening and pathogen reduction

This mini-review analyzed two approaches to screening bacterial contamination and utilizing pathogen reduction technology (PRT) for Platelet concentrates (PCs). While the culture-based method is still considered the gold standard for detecting bacterial contamination in PCs, efforts in the past two decades to minimize transfusion-transmitted bacterial infections (TTBIs) have been insufficient to eliminate this infectious threat. PRTs have emerged as a crucial tool to enhance safety and mitigate these risks. The evidence suggests that the screening strategy for bacterial contamination is more successful in ensuring PC quality, decreasing the necessity for frequent transfusions, and improving resistance to platelet transfusion. Alternatively, the PRT approach is superior regarding PC safety. However, both methods are equally effective in managing bleeding. In conclusion, PRT can become a more prevalent means of safety for PCs compared to culture-based approaches and will soon comprehensively surpass culture-based bacterial contamination detection methods.

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.

Establishment of a stable proficiency testing matrix in transfusion microbiology in South Africa

Background

All medical laboratories must participate in proficiency testing (PT) programmes to ensure high-quality results. Proficiency testing samples mimic clinical samples; however, PT programmes for detection of bacteria in blood products are not routinely performed due to unavailability of matrix-equivalent samples.

Objective

The aim of this study was to develop and test a matrix-equivalent PT programme using blood products as the basis matrix.

Methods

A prospective cross-sectional study was conducted from April 2021 until June 2021, using 52 blood products comprising 36 pooled platelet and 16 red blood cell products at the South African National Blood Service PT laboratory in Gauteng. Products were manipulated into matrix-equivalent PT samples by spiking 42 products with known bacterial strains at specific concentrations and treating the remaining 10 products with preserving fluid containing antibiotics. The level of agreement between the researcher results and participating laboratories' results was assessed.

Results

Of the prepared matrices, 568 out of 572 (99%) were stable for 30 days. Bacteria could correctly be identified in spiked samples for up to 23 days. Samples treated with preserving fluid remained negative until day 30. For spiked samples, an average of 98% agreement (153/156) was achieved between the three participating laboratories when compared with the researcher's results; 100% agreement was achieved for unspiked samples. The kappa scores obtained from all tested variables presented with scores between 0.856 and 1.000, and the p-value was < 0.001 throughout.

Conclusion

The developed PT matrix was therefore stable and suitable to be implemented in transfusion microbiology.

What this study adds

This study demonstrated that a stable microbiology PT programme using platelets and red blood cells can be developed for use on bacterial detection analysers and could help to close the gap presented by unavailability of a blood PT matrix for transfusion microbiology.

Association of Staphylococcus aureus in platelet concentrates with skin diseases in blood donors: Limitations of cultural bacterial screening

BACKGROUND

Bacterial contamination in platelet concentrates (PCs) is a major problem in transfusion medicine. Contamination with Staphylococcus aureus is occasionally missed, even with cultural screening.

STUDY DESIGN AND METHODS

Donors implicated in S. aureus-contaminated PC were followed up. Skin and nasal swab specimens from six donors and S. aureus isolated from PCs related to these donors were subjected to multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) to determine the identity of bacteria. To evaluate the validity of the screening method using BacT/ALERT 3D, we spiked S. aureus and three other bacterial species as comparisons into PCs and investigated their growth pattern.

RESULTS

S. aureus was isolated from all nasal specimens and from the arm skin specimens of three donors with atopic dermatitis. In all cases, the S. aureus strains isolated from the PC and those from the nasal and skin specimens of the same donor showed concordant results using MLST and PFGE. In the spiking study, S. aureus showed irregular detectability over 24 to 48 h post-spike periods, whereas the three other bacterial species were detected in all culture bottles after a 24-h post-spike period.

DISCUSSION

The strain identity of S. aureus between donor and PC suggests that the contaminants were derived from those colonized in the donor. Furthermore, S. aureus yielded false-negative results using BacT/ALERT 3D.

Recent lessons learned for ex-vivo platelet production

PURPOSE OF REVIEW

Platelet transfusion can be life-saving but carries a risk of infection or alloimmunization and is limited by insufficient donor sources and restricted unit shelf life. Generating sufficient platelets in vitro to replace a unit of collected blood remains a challenge. Here, we examine the latest advances in the regulation of megakaryocyte maturation and expansion along with platelet formation and survival. We also discuss alternative therapies investigated to induce platelet production.

RECENT FINDINGS

Recent studies examined candidate niche cells in the bone marrow microenvironment for promoting platelet formation and developed an explant-based bioreactor to enhance platelet production ex vivo. Chemical inhibitors were examined for their ability to promote megakaryocyte maturation and expansion. Microparticles from megakaryocytes or platelets were found to improve megakaryocyte maturation and platelet formation. Membrane budding was identified as a novel mode of platelet formation. Lastly, a chemical inhibitor to improve cold-stored platelets was identified.

SUMMARY

Recent advances in the regulation of megakaryocyte expansion and platelet production provide exciting promise for the development of improved approaches to generate platelets in vitro. These findings bring the field one step closer to achieving the ultimate goal of creating a unit of platelets without the need for donation.

Estimating the impact on the inventory of implementing pathogen-reduced platelets in Canada

BACKGROUND

Pathogen reduction (PR) technology will be implemented in pooled platelets in Canada. It is anticipated that PR platelets will be licensed in Canada for a maximum shelf life of 5 days, while non-treated apheresis platelet products will continue to be licensed for 7 days.

STUDY DESIGN AND METHODS

This study evaluates the impact on inventory, wastage, and shortages of implementing PR platelets. A custom-built simulation model was used to represent a regional distribution network. Experiments with the model were used to estimate product wastage and shortages when a 5-day PR pooled platelet product is introduced alongside a 7-day apheresis platelet product.

RESULTS

Pooled platelet waste and shortages both increase as pooled shelf life decreases. Apheresis platelets, however, show a different response: While shortages of apheresis platelets increase as the shelf life of pooled units decreases, apheresis waste declines as pooled shelf life decreases.

CONCLUSION

Additional platelet collections will be necessary to accommodate the shorter PR platelet shelf life and to cover increased patient transfusion needs due to a lower platelet yield in PR units. Increases of 9% for pooled units and 6% for apheresis units beyond expected demand, were found to be sufficient to ensure a non-inferior level of customer service while minimizing waste.

Transfusion-associated adverse events and implementation of blood safety measures - findings from the 2017 National Blood Collection and Utilization Survey

BACKGROUND

Serious transfusion-associated adverse events are rare in the United States. To enhance blood safety, various measures have been developed. With use of data from the 2017 National Blood Collection and Utilization Survey (NBCUS), we describe the rate of transfusion-associated adverse events and the implementation of specific blood safety measures.

STUDY DESIGN AND METHODS

Data from the 2017 NBCUS were used with comparison to already published estimates from 2015. Survey weighting and imputation were used to obtain national estimates of transfusion-associated adverse events, and the number of units treated with pathogen reduction technology (PRT), screened for Babesia, and leukoreduced.

RESULTS

The rate of transfusion-associated adverse events requiring any diagnostic or therapeutic interventions was stable (275 reactions per 100,000 transfusions in 2015 and 282 reactions per 100,000 transfusions in 2017). In 2017 among US blood collection centers, 16 of 141 (11.3%) reported screening units for Babesia and 28 of 144 (19.4%) reported PRT implementation; 138 of 2279 (6.1%) hospitals reported transfusing PRT-treated platelets. In 2017, 134 of 2336 (5.7%) hospitals reported performing secondary bacterial testing of platelets (50,922 culture-based and 63,220 rapid immunoassay tests); in 2015, 71 of 1877 (3.8%) hospitals performed secondary testing (87,155 culture-based and 21,779 rapid immunoassay tests). Nearly all whole blood/red blood cell units and platelet units were leukoreduced.

CONCLUSIONS

Besides leukoreduction, implementation of most blood safety measures reported in this study remains low. Nationally, hospitals might be shifting from culture-based secondary bacterial testing to rapid immunoassays.

Buffy coat pooled platelet concentrate: A new age platelet component

BACKGROUND

Buffy coat pooled platelet concentrate (BCPP) is a new blood component mainly used in Europe, which has good attributes of both random donor platelets and apheresis platelets in terms of high platelet count, leukoreduced and available in emergency. We planned this study to compare quality parameters and biochemical activation markers among buffy coat pooled platelets and apheresis platelet concentrate (AP-PC) to establish the quality and safety of this new blood component during storage.

MATERIALS AND METHODS

Three different preparations of BCPP were prepared: Nonleukoreduced (BCPP Part A), leukoreduced (BCPP Part B), and leukoreduced with platelet additive solution (PAS) (BCPP Part C) using a pool of 15 ABO-matched, nonreactive buffy-coats in each experiment to avoid any donor-related variations. Ten such experiments were done. Each BCPP was equivalent to 5 buffy coat units. Ten apheresis platelets were taken as control. Serial samplings were done on day 0, 3, and 5 of collection and were assessed for: volume, platelet count, white blood cell count, swirling, pH, sterility, glucose, lactate, soluble p-selectin, Interleukin (IL)-6, IL-1 β, and tumor necrosis factor alpha (TNF-α).

RESULTS

BCPP Part C (leukoreduced with PAS) maintained the best quality parameters in terms of maintenance of pH, least lactate accumulation, least sP-selectin levels, and least accumulation of inflammatory mediators (IL-6, IL-1 β, and TNF-α) than the other groups >BCPP part B >AP-PC and >BCPP Part A. On day 5 of storage pH for BCPP Part A, Part B, Part C, and AP-PC was: 6.33, 6.42, 6.64, and 6.29, respectively, and soluble p-selectin (ng/ml) was 201 ± 22, 186 ± 11, 149 ± 18, 200 ± 23, respectively. BCPP Part B and AP-PC had comparable quality parameters and activation markers.

CONCLUSIONS

Buffy coat pooled platelet has comparable and even better-quality control parameters (especially leukofiltered with PAS) than conventional platelet preparation and is a good alternative for meeting platelet transfusion requirements of critical patients during emergency hours in resource-constraint setting.

Platelet Component False Positive Detection Rate in Aerobic and Anaerobic Primary Culture: A Systematic Review and Meta-Analysis

Septic reactions from platelet transfusions are one of the leading causes of transfusion-associated mortality. The FDA guidance for platelet bacterial risk control includes bacterial culture using both aerobic and anaerobic bottles. Several studies have reported false positive rates (FPR) of culture, but these data have not been summarized or influencing factors analyzed. A systematic review and meta-analysis was performed according to published guidelines to assess the false positive rate and influencing factors. Eighteen studies were included for analysis. The combined aerobic/anaerobic FPR was 2.4 events per thousand (EPT) with a prediction interval of 0.5 to 5.7, while the aerobic FPR rate was 1.0 EPT (prediction interval: 0.2-2.2) and the anaerobic rate was 1.8 EPT. Estimates were based on a total of almost 5 million units tested. The rate of false positives due to instrument error was between 0.5-1.7 EPT, while it was between 0.3-1.0 EPT for sampling contamination based on whether only aerobic, anaerobic, or aerobic/anaerobic cultures were performed. The FPR is approximately 2 to 5 times higher than the literature reported true positive rate of 0.5 EPT.

Cryopreservation of platelets treated with riboflavin and UV light and stored at -80°C for 1 year

BACKGROUND

The combination of pathogen reduction technologies (PRTs) and cryopreservation can contribute to building a safe and durable platelet (PLT) inventory. Information about cryopreserved riboflavin and UV light-treated PLTs is scarce.

STUDY DESIGN AND METHODS

Twenty-four buffy coat (BC) PLT concentrates were grouped into 12 type-matched pairs, pooled, and divided into 12 non-PRT-treated control units and 12 riboflavin and UV light PRT-treated test units. Both were cryopreserved with 5% DMSO and stored at -80°C for 1 year. The cryopreservation method used was designed to avoid the formation of aggregates. PLT variables (PLT recovery, swirling, pH, MPV, and LDH) and hemostatic function measured by thromboelastography (TEG) were analyzed before cryopreservation (day 1) and post-cryopreservation at day 14 and months 3, 6, and 12 of storage at -80°C. The analyses were carried out within 1-h post-thaw.

RESULTS

No aggregates were found in either PLT group at any time. Swirling was observed in both groups. MPV increased and mean pH values decreased over time (p < .001), but the mean pH value was never below 6.4 in either group after 12 months of storage at -80°C. PLT recovery was good and clotting time became significantly shorter over the storage period in both groups (p < .001).

CONCLUSION

Our cryopreservation and thawing method prevented aggregate formation in cryopreserved riboflavin-UV-light-treated PLTs, which exhibited good recovery, swirling, pH > 6.4, and procoagulant potential, as evidenced by a reduced clotting time after 12 months of storage at -80°C. The clinical relevance of these findings should be further investigated in clinical trials.

Evaluation of riboflavin and ultraviolet light treatment against Klebsiella pneumoniae in whole blood-derived platelets: A pilot study

BACKGROUND

Bacterial contamination of platelet concentrates (PCs) is the predominant cause of infectious transfusion reactions. The Pathogen Inactivation Mirasol system was implemented at the King Faisal Specialist Hospital (Saudi Arabia) to reduce the risk of transfusing contaminated PCs. This pilot study evaluated the effectiveness of Mirasol against Klebsiella pneumoniae, a pathogen associated with transfusion reactions, in whole blood-derived PCs.

STUDY DESIGN AND METHODS

Whole blood (WB) units inoculated with one of six K. pneumoniae strains (five clinical isolates and ATCC-700603) at a concentration of 3-38 CFU/unit, were processed using the platelet-rich plasma (PRP) method. Each spiked PC was pooled with four unspiked units. The pooled PC was split into three Mirasol storage bags: an untreated unit (control), and two units treated with Mirasol at 26 and 32 h post-WB collection, respectively. PC samples obtained before and after Mirasol treatment were used for BacT/ALERT cultures and determination of bacteria quantification. Each experiment was repeated three independent times.

RESULTS

Five strains were detected prior to PC treatment (24 h post-WB spiking), while one clinical isolate was not detected. Mirasol treatment after 26 h of WB collection resulted in complete inactivation of all K. pneumoniae strains. However, treatment 32 h post-WB collection resulted in the breakthrough of one clinical isolate in two of the three replicates with ~7.8 log₁₀ CFU/unit detected on day 5 of PC storage.

CONCLUSION

Delayed Mirasol treatment from 26 to 32 h post-WB collection, resulted in one breakthrough. These results highlight the importance of minimizing the time between WB collection and PI treatment.

Residual bacterial detection rates after primary culture as determined by secondary culture and rapid testing in platelet components: A systematic review and meta-analysis

BACKGROUND

Primary culture alone was a bacterial risk control strategy intended to facilitate interdiction of contaminated platelets (PLTs). A September 2019 FDA guidance includes secondary testing options to enhance safety. Our objective was to use meta-analysis to determine residual contamination risk after primary culture using secondary culture and rapid testing.

STUDY DESIGN AND METHODS

A December 2019 literature search identified articles on PLT bacterial detection rates using primary culture and a secondary testing method. We used meta-analysis to estimate secondary testing detection rates after a negative primary culture. We evaluated collection method, sample volume, sample time, and study date as potential sources of heterogeneity.

RESULTS

The search identified 6102 articles; 16 were included for meta-analysis. Of these, 12 used culture and five used rapid testing as a secondary testing method. Meta-analysis was based on a total of 103 968 components tested by secondary culture and 114 697 by rapid testing. The residual detection rate using secondary culture (DR_SC ) was 0.93 (95% CI, 0.24-0.6) per 1000 components, while residual detection rate using rapid testing (DR_RT ) was 0.09 (95% CI, 0.01-0.25) per 1000 components. Primary culture detection rate was the only statistically significant source of heterogeneity.

CONCLUSION

We evaluated bacterial detection rates after primary culture using rapid testing and secondary culture. These results provide a lower and upper bound on real-world residual clinical risk because these methods are designed to detect high-level exposures or any level of exposure, respectively. Rapid testing may miss some harmful exposures and secondary culture may identify some clinically insignificant exposures.

The comparative safety of bacterial risk control strategies for platelet components: a simulation study

BACKGROUND

Bacterial contamination of platelets is a problem that can lead to harmful septic transfusion reactions. The US Food and Drug Administration published a guidance in September 2019 detailing several permissible risk control strategies. Our objective was to compare the safety of each bacterial testing strategy for apheresis platelets.

STUDY DESIGN AND METHODS

We used simulation to compare safety of the nine risk control strategies involving apheresis platelet testing. The primary outcome was the risk of exposure. An exposure event occurred if a patient received platelets exceeding a specific contamination threshold (>0, 10³ , and 10⁵ colony-forming units (CFU/mL). We generated a range of bacterial contamination scenarios (inoculum size, doubling time, lag time) and compared risk of exposure for each policy in each contamination scenario. We then computed the average risk difference over all scenarios.

RESULTS

At the 0 CFU/mL exposure threshold, two-step policies that used secondary culture ranked best (all top three), while single-step 24-hour culture with 3-day expiration ranked last (ninth). This latter policy performed well (median rank of 1) at both the 10³ and 10⁵ CFU/mL thresholds, but 48-hour culture with 7-day expiration performed relatively poorly. At these higher thresholds, median ranks of two-step policies that used secondary culture were again top three. Two-step policies that used rapid testing improved at the higher (10⁵ CFU/mL) harm threshold, with median rankings between 1 and 5.

CONCLUSION

Two-step policies that used secondary culture were generally safer than single-step policies. Performance of two-step policies that used rapid testing depended on the CFU per milliter threshold of exposure used.

Haemostatic function measured by thromboelastography and metabolic activity of platelets treated with riboflavin and UV light

BACKGROUND

Pathogen reduction technology (PRT) may damage platelet (PLT) components. To study this, metabolic activity and haemostatic function of buffy coat (BC) PLT concentrates, with or without riboflavin and UV light PRT treatment, were compared.

MATERIAL AND METHODS

Twenty-four BC PLT concentrates, leukoreduced and diluted in additive solution, were grouped into 12 type-matched pairs, which were pooled and divided into 12 non-PRT-treated BC PLT concentrates (control units) and 12 riboflavin and UV PRT-treated BC PLT concentrates (test units). Haemostatic function and metabolic parameters were monitored by thrombelastography at days 1, 3, 7 and 14 post collection in both PLT groups.

RESULTS

Loss of PLT discoid shape, glucose consumption, lactate production, and decrease in pH were greater in the PRT-treated PLTs than in control PLTs over time (p<0.001). PLT haemostatic function evaluated by clot strength was also significantly weaker in PRT-treated PLTs compared with the excellent clot quality of control PLTs at day 7 (maximum amplitude: 41.27 vs 64.27; p<0.001), and even at day 14 (21.16 vs 60.39; p<0.001) of storage.

DISCUSSION

Pathogen reduction technology treatment accelerates and increases platelet storage lesion, resulting in glucose depletion, lactate accumulation, PLT acidification, and discoid shape loss. The clots produced by control PLTs at day 14 were still remarkably strong, whereas at day 7 PRT-treated PLTs produced weaker clots compared to the control group. Clinical trials investigating the efficacy of PRT-treated PLTs transfused at the end of the storage period (day 7), when the in vitro clot strength is weaker, are needed.

Adoption trends of point of issue Verax PGD rapid test for bacterial screening of platelets between 2013 and 2018 among hospitals supplied by the American Red Cross and impact on platelet availability

BACKGROUND

Point-of-issue tests, such as the Verax Pan Genera Detection (PGD) test, can be used to mitigate the occurrence of septic reactions. Little is known about how widespread the adoption of the PGD test is across US hospitals.

STUDY DESIGN/METHODS

The Red Cross hemovigilance database was used to determine the numbers of PGD-positive test results between 2013 and 2018. An examination of the impact of a reactive PGD test on product availability was performed for 2018.

RESULTS

The number of reported cases doubled, rising from approximately 50 to 100 per year between 2013 and 2018. A total of 475 initially reactive PGD tests during the entire study period were reported, and 7 (1.5%) of these were determined to be true positives. Hospitals surveyed reported testing platelet units once, with no repeat testing if the unit was PGD reactive. Evaluation of the reported PGD reactive cases for apheresis platelets for 2018 (n = 93) resulted in an estimated cost to the blood center of $87,000, which included the labor and material costs of working up the cases and the estimated value of the lost 64 units and co-components. In addition, there was a loss of the opportunity to collect over 85 apheresis platelets during the time the implicated donor was temporarily deferred.

CONCLUSIONS

The number of hospital reports of reactive PGD tests has shown modest growth in the past 5 years. The number of initially reactive PGD tests that were confirmed was minimal. Blood centers can incur cost and platelet inventory loss from initially false-positive test results.

Bacterial contamination rate of platelet components by primary culture: a systematic review and meta-analysis

BACKGROUND

Platelets have the highest bacterial contamination risk of all blood components, and septic transfusion reactions remain a problem. A good estimate of contamination rates could provide information about residual risk and inform optimal testing strategies. We performed a systematic review and meta-analysis of platelet contamination rates by primary culture.

STUDY DESIGN AND METHODS

A literature search in December 2019 identified articles on platelet contamination rates using primary culture. We used meta-analysis to estimate the overall rate of contamination and meta-regression to identify heterogeneity. We studied the following sources of heterogeneity: collection method, sample volume, positivity criteria, and study date. Contamination rate estimates were obtained for apheresis (AP), platelet rich plasma (PRP), and buffy coat (BC) collection methods.

RESULTS

The search identified 6102 studies, and 22 were included for meta-analysis. Among these 22 studies, there were 21 AP cohorts (4,072,022 components), 4 PRP cohorts (138,869 components), and 15 BC cohorts (1,474,679 components). The overall mean contamination rate per 1000 components was 0.51 (95% CI: 0.38-0.67) including AP (0.23, 95% CI: 0.18-0.28), PRP, (0.38, 95% CI: 0.15-0.70), and BC (1.12, 95% CI: 0.51-1.96). There was considerable variability within each collection method. Sample volume, positivity criteria, and publication year were significant sources of heterogeneity.

CONCLUSION

The bacterial contamination rate of platelets by primary culture is 1 in 1961. AP and PRP components showed a lower contamination rate than BC components. There is clinically significant between-study variability for each method. Larger sample volumes increased sensitivity, and bacterial contamination rates have decreased over time.

Bacterial contamination and septic transfusion reaction rates associated with platelet components before and after introduction of primary culture: experience at a US Academic Medical Center 1991 through 2017

BACKGROUND

The high incidence of septic transfusion reactions (STRs) led to testing being mandated by AABB from 2004. This was implemented by primary culture of single-donor apheresis platelets (APs) from 2004 and prestorage pooled platelets (PSPPs) from 2007.

STUDY DESIGN/METHODS

Platelet (PLT) aliquots were cultured at issue and transfusion reactions evaluated at our hospital. Bacterial contamination and STR rates (shown as rates per million transfusions in Results) were evaluated before and after introduction of primary culture by blood centers that used a microbial detection system (BacT/ALERT, bioMerieux) or enhanced bacterial detection system (eBDS, Haemonetics).

RESULTS

A total of 28,457 PLTs were cultured during pre-primary culture periods (44.7% APs; 55.3% at-issue pooled PLTs [AIPPs]) and 97,595 during post-primary culture periods (79.3% APs; 20.7% PSPPs). Forty-three contaminated units were identified in preculture and 34 in postculture periods (rates, 1511 vs. 348; p < 0.0001). Contamination rates of APs were significantly lower than AIPPs in the preculture (393 vs. 2415; p < 0.0001) but not postculture period compared to PSPPs (387 vs. 198; p = 0.9). STR rates (79 vs. 90; p = 0.98) were unchanged with APs but decreased considerably with pooled PLTs (826 vs. 50; p = 0.0006). Contamination (299 vs. 324; p = 0.84) and STR rates (25 vs. 116; p = 0.22) were similar for PLTs tested by BacT/ALERT and eBDS primary culture methods. A change in donor skin preparation method in 2012 was associated with decreased contamination and STR rates.

CONCLUSION

Primary culture significantly reduced bacterial contamination and STR associated with pooled but not AP PLTs. Measures such as secondary testing near time of use or pathogen reduction are needed to further reduce STRs.

Platelet safety strategies in Japan: impact of short shelf life on the incidence of septic reactions

BACKGROUND

Transfusion-transmitted bacterial infections (TTBIs) often have serious consequences for patients. The Japanese Red Cross (JRC) has not implemented culture screening for platelet concentrate (PC), but it has maintained a shelf life of 85 hours for PC.

STUDY DESIGN AND METHODS

The JRC collected reports of suspected TTBI and investigated causal relationships using PC samples and patient blood samples. PCs showing apparent abnormalities were retrieved and cultured and analyzed for bacterial growth.

RESULTS

The JRC analyzed 86 samples available from 135 transfused PCs with suspected TTBIs that were collected over the past 12 years; 17 (19.8%) were culture-positive. One, 6, and 10 TTBIs developed in patients on Days 1, 2, and 3 after PC collection, respectively. Assuming that PC is transfused on the day of issue, the TTBI risk was fourfold higher on Day 3 than on Day 2, after adjusting the TTBI incidence for the number of PCs issued per day. Compared with the model of issuing all PCs on Day 3, issuing PCs with the current distribution of storage time could have decreased the TTBI incidence by 56%. During the past 8 years, the JRC retrieved 960 PC units because of apparent abnormalities, 2.8% of which were culture-positive.

CONCLUSION

The short shelf life of PC is associated with a low incidence of reported TTBIs, more than half of which occurred on Day 3 relative to earlier time points. Visual inspection of PC before transfusion is crucial in detecting bacterially contaminated PC despite its low positive predictive value.

Non-ionizing 405 nm Light as a Potential Bactericidal Technology for Platelet Safety: Evaluation of in vitro Bacterial Inactivation and in vivo Platelet Recovery in Severe Combined Immunodeficient Mice

Bacterial contamination of ex vivo stored platelets is a cause of transfusion-transmitted infection. Violet-blue 405 nm light has recently demonstrated efficacy in reducing the bacterial burden in blood plasma, and its operational benefits such as non-ionizing nature, penetrability, and non-requirement for photosensitizing agents, provide a unique opportunity to develop this treatment for in situ treatment of ex vivo stored platelets as a tool for bacterial reduction. Sealed bags of platelet concentrates, seeded with low-level Staphylococcus aureus contamination, were 405 nm light-treated (3–10 mWcm⁻²) up to 8 h. Antimicrobial efficacy and dose efficiency was evaluated by quantification of the post-treatment surviving bacterial contamination levels. Platelets treated with 10 mWcm⁻² for 8 h were further evaluated for survival and recovery in severe combined immunodeficient (SCID) mice. Significant inactivation of bacteria in platelet concentrates was achieved using all irradiance levels, with 99.6–100% inactivation achieved by 8 h (P < 0.05). Analysis of applied dose demonstrated that lower irradiance levels generally resulted in significant decontamination at lower doses: 180 Jcm⁻²/10 mWcm⁻² (P = 0.008) compared to 43.2 Jcm⁻²/3 mWcm⁻² (P = 0.002). Additionally, the recovery of light-treated platelets, compared to non-treated platelets, in the murine model showed no significant differences (P = >0.05). This report paves the way for further comprehensive studies to test 405 nm light treatment as a bactericidal technology for stored platelets.

A suspected septic transfusion reaction associated with posttransfusion contamination of a platelet pool by vancomycin-resistant Enterococcus faecium

BACKGROUND

Vancomycin-resistant enterococci (VRE) are antibiotic-resistant organisms associated with both colonization and serious life-threatening infection in health care settings. Contamination of platelet concentrates (PCs) with Enterococcus can result in transfusion-transmitted infection.

CASE PRESENTATION

This report describes the investigation of a septic transfusion case involving a 27-year-old male patient with relapsed acute leukemia who was transfused with a 5-day-old buffy coat PC pool and developed fever and rigors.

DISCUSSION

Microbiology testing and pulse-field gel electrophoresis (PFGE) was done on patient blood cultures obtained from peripheral and central lines. Microbiology and molecular testing were also performed on the remaining posttransfusion PC pool, which was refrigerated for 24 hours before microbiology testing. Red blood cell (RBC) and plasma units associated with the implicated PCs were screened for microbial contamination. Patient blood cultures obtained from peripheral and central lines yielded vancomycin-resistant Enterococcus faecium. Gram stain of a sample from the platelet pool was negative but coagulase-negative Staphylococcus (CNST) and VRE were isolated on culture. Antibiotic sensitivity and PFGE profiles of several VRE isolates from the patient before and after transfusion, and the PC pool, revealed that all were closely related. Associated RBC and plasma components tested negative for microbial contamination.

CONCLUSIONS

Microbiological and molecular investigations showed a relationship between VRE isolated from the patient before and after transfusion, and therefore it is postulated that a patient-to-PC retrograde contamination (from either blood or skin) occurred. As the CNST isolated from the PC pool was not isolated from patient samples, its implication in the transfusion event is unknown.

Metagenomic analysis of potential pathogens from blood donors in Guangzhou, China

OBJECTIVES

This study aimed to identify the emerging/reemerging pathogens in blood donation samples.

BACKGROUND

A metagenomic analysis has previously been used to look for pathogens but in this study, the relationship with aminotransferase (ALT) is described.

METHODS/MATERIALS

Excluding samples reactive to hepatitis B virus, hepatitis C virus, human immunodeficiency syndrome virus or syphilis and plasma samples were stratified into three groups of ALT levels (IU/L): A ≤ 50, B 51 to 69 and C ≥ 70, respectively. Each group was mixed in a pool of 100 samples, from which DNA and cDNA libraries were established for next generation sequencing and analysis. Pathogens of interest were identified by immunoassays, nested-polymerase chain reaction, phylogenetic analysis and pathogen detection in follow-up donors.

RESULTS

Several new or reemerging transfusion-transmitted pathogens were identified; Streptococcus suis, Babesia species and Toxoplasma gondii were found in the three ALT groups, Epstein-Barr virus (EBV) only in group C. Ten S. suis nucleic acid positive samples were detected, all closely phylogenetically related to reference strains. A donor in group A carried both S. suis genome and specific IgM in follow-up samples. This strain was identified as nontoxic S. suis. Five samples contained a short fragment of Babesia species SpeI-AvaI gene, while T. gondii was identified in 20 samples as a short fragment of 18S rDNA gene. In group C, two samples contained EBV genome.

CONCLUSIONS

Blood donations that contained S. suis, Babesia species and T. gondii sequences might represent potential transfusion risks. EBV, a potential cause of elevated ALT, was detected. Metagenomic analysis might be a useful technology for monitoring blood safety.

Platelet transfusion: Alloimmunization and refractoriness

The transfusion of platelets for both prophylaxis and treatment of bleeding is relevant to all areas of medicine and surgery. Historically, guidance regarding platelet transfusion has been limited by a lack of good quality clinical trials and so has been based largely on expert opinion. In recent years however there has been renewed interest in methods to prevent and treat hemorrhage, and the field has benefited from a number of large clinical trials. Some studies, such as platelet transfusion versus standard care after acute stroke due to spontaneous cerebral haemorrhage associated with antiplatelet therapy (PATCH) and platelets for neonatal transfusion Study 2 (PLANET-2), have reported an increased risk of harm with platelet transfusion in specific patient groups. These studies suggest a wider role of platelets beyond hemostasis, and highlight the need for further clinical trials to better understand the risks and benefits of platelet transfusions. This review evaluates the indications for platelet transfusion, both prophylactic and therapeutic, in the light of recent studies and clinical trials. It highlights new developments in the fields of platelet storage and platelet substitutes, and novel ways to avoid complications associated with platelet transfusions. Lastly, it reviews initiatives designed to reduce inappropriate use of platelet transfusions and to preserve this valuable resource for situations where there is evidence for their beneficial effect.

Microbiological Screening of Platelet Concentrates in Europe

The risk of transfusion-associated sepsis due to transmission of bacteria is a persistent problem in the transfusion field. Despite numerous interventions to reduce the risk, cases of bacterial sepsis following transfusion are repeatedly being reported. Especially platelet concentrates are highly susceptible to bacterial contaminations due to the growth-promoting storage conditions. In Europe, blood establishments and national authorities have implemented individual precaution measures to mitigate the risk of bacterial transmission. To obtain an overview of the different approaches, we compiled information from national authorities, blood establishments, and the current literature. Several aspects such as the shelf life of platelets, time of sampling and the applied control measures are compared between the member states. The analysis of the data revealed a broad heterogeneity of procedures on a national level ranging from platelet release without any safety testing up to mandatory screening of all platelet concentrates prior to transfusion. Despite the substantial progress made in recent years, several bacterial reports on transfusion-associated sepsis indicate that further efforts are needed to increase the safety of blood transfusions in the long term.

Transfusion-Transmitted Infections Reported to the National Healthcare Safety Network Hemovigilance Module

Transfusion-transmitted infections (TTIs) can be severe and result in death. Transfusion-transmitted viral pathogen transmission has been substantially reduced, whereas sepsis due to bacterial contamination of platelets and transfusion-transmitted babesiosis may occur more frequently. Quantifying the burden of TTI is important to develop targeted interventions. From January 1, 2010, to December 31, 2016, health care facilities participating in the National Healthcare Safety Network Hemovigilance Module monitored transfusion recipients for evidence of TTI and recorded the total number of units transfused. Facilities use standard criteria to report TTIs. Incidence rates of TTIs, including for bacterial contamination of platelets and transfusion-transmitted babesiosis, are presented. One hundred ninety-five facilities reported 111 TTIs and 7.9 million transfused components to the National Healthcare Safety Network Hemovigilance Module. Of these 111 reports, 54 met inclusion criteria. The most frequently reported pathogens were Babesia spp in RBCs (16/23, 70%) and Staphylococcus aureus in platelets (12/30, 40%). There were 1.95 (26 apheresis, 4 whole blood derived) TTIs per 100 000 transfused platelet units and 0.53 TTI per 100 000 transfused RBC components, compared to 0.68 TTI per 100 000 all transfused components. Bacterial contamination of platelets and transfusion-transmitted babesiosis were the most frequently reported TTIs. Interventions that reduce the burden of bacterial contamination of platelets, particularly collected by apheresis, and Babesia transmission through RBC transfusion would reduce transfusion recipient morbidity and mortality. These analyses demonstrate the value and importance of facility participation in national recipient hemovigilance using standard reporting criteria.

The peptidoglycan and biofilm matrix of Staphylococcus epidermidis undergo structural changes when exposed to human platelets

Staphylococcus epidermidis is a bacterium frequently isolated from contaminated platelet concentrates (PCs), a blood product used to treat bleeding disorders in transfusion patients. PCs offer an accidental niche for colonization of S. epidermidis by forming biofilms and thus avoiding clearance by immune factors present in this milieu. Using biochemical and microscopy techniques, we investigated the structural changes of the peptidoglycan (PG) and the biofilm matrix of S. epidermidis biofilms formed in whole-blood derived PCs compared to biofilms grown in glucose-supplemented trypticase soy broth (TSBg). Both, the PG and the biofilm matrix are primary mechanisms of defense against environmental stress. Here we show that in PCs, the S. epidermidis biofilm matrix is mainly of a proteinaceous nature with extracellular DNA, in contrast to the predominant polysaccharide nature of the biofilm matrix formed in TSBg cultures. PG profile studies demonstrated that the PG of biofilm cells remodels during PC storage displaying fewer muropeptides variants than those observed in TSBg. The PG muropeptides contain two chemical modifications (amidation and O-acetylation) previously associated with resistance to antimicrobial agents by other staphylococci. Our study highlights two key structural features of S. epidermidis that are remodeled when exposed to human platelets and could be used as targets to reduce septic transfusions events.

Financial impact of alternative approaches to reduce bacterial contamination of platelet transfusions

BACKGROUND

Bacterial contamination of platelets remains the leading infectious risk from blood transfusion. Pathogen reduction (PR), point-of-release testing (PORt), and secondary bacterial culture (SBC) have been proposed as alternative risk control strategies, but a comprehensive financial comparison has not been conducted.

STUDY DESIGN AND METHODS

A Markov-based decision tree was constructed to model the financial and clinical impact of PR, PORt, and SBC, as well as a baseline strategy involving routine testing only. Hospitals were assumed to acquire leukoreduced apheresis platelets on Day 3 after collection, and, in the base case analysis, expiration would occur at the end of Day 5 (PR and SBC) or 7 (PORt). Monte Carlo simulations assessed the direct medical costs for platelet acquisition, testing, transfusion, and possible complications. Input parameters, including test sensitivity and specificity, were drawn from existing literature, and costs (2018 US dollars) were based on a hospital perspective.

RESULTS

The total costs per unit acquired by the hospital under the baseline strategy, PR, PORt, and SBC were $651.45, $827.82, $686.33, and $668.50, respectively. All risk-reduction strategies decreased septic transfusion reactions and associated expenses, with the greatest reductions from PR. PR would add $191.09 in per-unit acquisition costs, whereas PORt and SBC would increase per-unit testing costs by $31.79 and $17.26, respectively. Financial outcomes were sensitive to platelet dating; allowing 7-day storage with SBC would lead to a cost savings of $12.41 per transfused unit. Results remained robust in probabilistic sensitivity analyses.

CONCLUSIONS

All three strategies are viable approaches to reducing bacterially contaminated platelet transfusions, although SBC is likely to be the cheapest overall.

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.

Atypical Bacterial Growth within Units of Platelets Challenges Transfusion Medicine Dogma

Although transfusion-transmitted bacterial infection is relatively rare, mitigation of bacterial contamination of platelet units is arguably the top current transfusion-related safety concern. Several different technologies have been employed to detect or neutralize bacteria in platelet concentrates. However, studies of the efficacy of these systems have been hampered by problematic definitions of what represents a "true-positive" versus a "false-positive" culture result. In the current issue of the Journal of Clinical Microbiology (M. Cloutier, M.-È. Nolin, H. Daoud, A. Jacques, M. J. de Grandmont, É Ducas, G. Delage, and L. Thibault, J Clin Microbiol 56:e01105-18, 2018, https://doi.org/10.1128/JCM.01105-18), it was demonstrated that the growth of Bordetella holmesii is inhibited by the platelet storage environment, which may explain why the results of initial positive platelet cultures are not always confirmed by subsequent cultures later during the storage period. This important finding is at odds with the generally held belief within the field of transfusion medicine that initially positive platelet cultures that are not confirmed on repeat testing are instrumentation-based false positives. The clinical risk profile of organisms demonstrating storage-related low viability is worthy of further study.

Combining culture and microbead-based immunoassay for the early and generic detection of bacteria in platelet concentrates

BACKGROUND

Despite current preventive strategies, bacterial contamination of platelets is the highest residual infectious risk in transfusion. Bacteria can grow from an initial concentration of 0.03-0.3 colony-forming units (CFUs)/mL up to 10⁸ to 10⁹ CFUs/mL over the product shelf life. The aim of this study was to develop a cost-effective approach for an early, rapid, sensitive, and generic detection of bacteria in platelet concentrates.

STUDY DESIGN AND METHODS

A large panel of bacteria involved in transfusion reactions, including clinical isolates and reference strains, was established. Sampling was performed 24 hours after platelet spiking. After an optimized culture step for increasing bacterial growth, a microbead-based immunoassay allowed the generic detection of bacteria. Antibody production and immunoassay development took place exclusively with bacteria spiked in fresh platelet concentrates to improve the specificity of the test.

RESULTS

Antibodies for the generic detection of either gram-negative or gram-positive bacteria were selected for the microbead-based immunoassay. Our approach, combining the improved culture step with the immunoassay, allowed sensitive detection of 1 to 10 CFUs/mL for gram-negative and 1 to 10² CFUs/mL for gram-positive species.

CONCLUSION

In this study, a new approach combining bacterial culture with immunoassay was developed for the generic and sensitive detection of bacteria in platelet concentrates. This efficient and easily automatable approach allows tested platelets to be used on Day 2 after collection and could represent an alternative strategy for reducing the risk of transfusion-transmitted bacterial infections. This strategy could be adapted for the detection of bacteria in other cellular products.

Towards increasing shelf life and haemostatic potency of stored platelet concentrates

PURPOSE OF REVIEW

Platelet transfusion is a widely used therapy in treating or preventing bleeding and haemorrhage in patients with thrombocytopenia or trauma. Compared with the relative ease of platelet transfusion, current practice for the storage of platelets is inefficient, costly and relatively unsafe, with platelets stored at room temperature (RT) for upto 5-7 days.

RECENT FINDINGS

During storage, especially at cold temperatures, platelets undergo progressive and deleterious changes, collectively termed the 'platelet storage lesion', which decrease their haemostatic function and posttransfusion survival. Recent progress in understanding platelet activation and host clearance mechanisms is leading to the consideration of both old and novel storage conditions that use refrigeration and/or cryopreservation to overcome various storage lesions and significantly extend platelet shelf-life with a reduced risk of pathogen contamination.

SUMMARY

A review of the advantages and disadvantages of alternative methods for platelet storage is presented from both a clinical and biological perspective. It is anticipated that future platelet preservation involving cold, frozen and/or pathogen reduction strategies in a proper platelet additive solution will enable longer term and safer platelet storage.

Bacterial contamination of platelets for transfusion: strategies for prevention

Platelet transfusions carry greater risks of infection, sepsis, and death than any other blood product, owing primarily to bacterial contamination. Many patients may be at particular risk, including critically ill patients in the intensive care unit. This narrative review provides an overview of the problem and an update on strategies for the prevention, detection, and reduction/inactivation of bacterial contaminants in platelets. Bacterial contamination and septic transfusion reactions are major sources of morbidity and mortality. Between 1:1000 and 1:2500 platelet units are bacterially contaminated. The skin bacterial microflora is a primary source of contamination, and enteric contaminants are rare but may be clinically devastating, while platelet storage conditions can support bacterial growth. Donor selection, blood diversion, and hemovigilance are effective but have limitations. Biofilm-producing species can adhere to biological and non-biological surfaces and evade detection. Primary bacterial culture testing of apheresis platelets is in routine use in the US. Pathogen reduction/inactivation technologies compatible with platelets use ultraviolet light-based mechanisms to target nucleic acids of contaminating bacteria and other pathogens. These methods have demonstrated safety and efficacy and represent a proactive approach for inactivating contaminants before transfusion to prevent transfusion-transmitted infections. One system, which combines ultraviolet A and amotosalen for broad-spectrum pathogen inactivation, is approved in both the US and Europe. Current US Food and Drug Administration recommendations advocate enhanced bacterial testing or pathogen reduction/inactivation strategies (or both) to further improve platelet safety. Risks of bacterial contamination of platelets and transfusion-transmitted infections have been significantly mitigated, but not eliminated, by improvements in prevention and detection strategies. Regulatory-approved technologies for pathogen reduction/inactivation have further enhanced the safety of platelet transfusions. Ongoing development of these technologies holds great promise.

Failure of bacterial screening to detect Staphylococcus aureus: the English experience of donor follow-up

BACKGROUND AND OBJECTIVES

Between February 2011 and December 2016, over 1·6 million platelet units, 36% pooled platelets, underwent bacterial screening prior to issue. Contamination rates for apheresis and pooled platelets were 0·02% and 0·07%, respectively. Staphylococcus aureus accounted for 21 contaminations, including four pooled platelets, one confirmed transfusion-transmitted infection (TTI) and three 'near-miss' incidents detected on visual inspection which were negative on screening. We describe follow-up investigations of 16 donors for skin carriage of S. aureus and molecular characterisation of donor and pack isolates.

MATERIALS AND METHODS

Units were screened by the BacT/ALERT 3D detection system. Contributing donors were interviewed and consent requested for skin and nasal swabbing. S. aureus isolates were referred for spa gene type and DNA macrorestriction profile to determine identity between carriage strains and packs.

RESULTS

Donors of 10 apheresis and two pooled packs screen positive for S. aureus were confirmed as the source of contamination; seven had a history of skin conditions, predominantly eczema; 11 were nasal carriers. The 'near-miss' incidents were associated with apheresis donors, two donors harboured strains indistinguishable from the pack strain. The TTI was due to a screen-negative pooled unit, and a nasal isolate of one donor was indistinguishable from that in the unit.

CONCLUSION

Staphylococcus aureus contamination is rare but potentially harmful in platelet units. Donor isolates showed almost universal correspondence in molecular type with pack isolates, thus confirming the source of contamination. The importance of visual inspection of packs prior to transfusion is underlined by the 'near-miss' incidents.

Transfusion-associated hazards: A revisit of their presentation

As a therapy or a support to other therapies, despite being largely beneficial to patients in general, transfusion it is not devoid of some risks. In a moderate number of cases, patients may manifest adverse reactions, otherwise referred to as transfusion-associated hazards (TAHs). The latest French 2016 haemovigilance report indicates that 93% of TAHs are minor (grade 1), 5.5% are moderate (grade 2) and 1.6% are severe (grade 3), with only five deaths (grade 4) being attributed to transfusion with relative certainty (imputability of level [or grade] 1 to 3). Health-care providers need to be well aware of the benefits and potential risks (to best evaluate and discuss the benefit-risk ratio), how to prevent TAHs, the overall costs and the availability of alternative therapeutic options. In high-income countries, most blood establishments (BEs) and hospital blood banks (HBBs) have developed tools for reporting and analysing at least severe transfusion reactions. With nearly two decades of haemovigilance, transfusion reaction databases should be quite informative, though there are four main caveats that prevent it from being fully efficient: (ai) reporting is mainly declarative and is thus barely exhaustive even in countries where it is mandatory by law; (aii) it is often difficult to differentiate between the different complications related to transfusion, diseases, comorbidities and other types of therapies in patients suffering from debilitating conditions; (aiii) there is a lack of consistency in the definitions used to describe and report some transfusion reactions, their severity and their likelihood of being related to transfusion; and (aiv) it is difficult to assess the imputability of a particular BC given to a patient who has previously received many BCs over a relatively short period of time. When compiling all available information published so far, it appears that TAHs can be analysed using different approaches: (bi) their pathophysiological nature; (bii) their severity; (biii) the onset scheme; (biv) a quality assessment (preventable or non-preventable); (bv) their impact on ongoing therapy. Moreover, TAHs can be reported either in a non-integrative or in an integrative way; in the latter case, presentation may also differ when issued by a blood establishment or a treating ward. At some point, a recapitulative document would be useful to gain a better understanding of TAHs in order to decrease their occurrence and severity and allow decision makers to determine action plans: this is what this review attempts to make. This review attempts to merge the different aspects, with a focus on the hospital side, i.e., how the most frequent TAHs can be avoided or mitigated.

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.