Monitoring of apheresis platelet bacterial contamination with an automated liquid culture system: a university experience

BACKGROUND: With 4 million platelet units transfused per year in the United States and with the current estimate of bacteria contamination rate in PLT units, it would be expected that 2000 to 4000 bacterially contaminated units are transfused and associated with 333 to 1000 cases of clinical sepsis. STUDY DESIGN AND METHODS: Apheresis platelets were sampled on Day 2 of storage (collection day=Day 0) and issue (or following outdate, Days 6-8) using a sterile connection device (SCD) to attach a sampling bag. Using aseptic technique and a laminar flow hood, bottles were inoculated and placed onto an automated liquid culture system (BacT/ALERT 3D Microbial Detection System) for 7 days. RESULTS: A total of 2397 apheresis PLT units were sampled. A triple apheresis collection was reactive within 14 hours of the Day 2 sampling (aerobic bottles) and the bags were removed from inventory. Staphylococcus epidermidis was identified in all three contaminated bags. Two double-apheresis collections were found to be contaminated with Proprionibacterium sp. after 6 days of incubation but had been transfused to four patients without discernible clinical sequelae. There was one false-positive aerobic bottle and one false-positive anaerobic result due to inadvertent contamination of a bottle. Thus, the overall true-positive rate was 7 of 2397 apheresis units (0.29%) with a true-positive rate for aerobic organisms of 0.13% and an anaerobic true-positive rate of 0.17%. The false-positive rate was 2 out of 4794 samplings (0.04%) or 2 out of 9588 bottles (0.02%). CONCLUSION: This preliminary data suggests that the use of a SCD, aseptic technique, and a laminar flow hood is associated with a low rate of contamination. In no case did an issue (or outdate) detect contamination that was not detected by the Day 2 culture. Additional surveillance is necessary before we can conclude that a Day 2 sterile culture is truly predictive of an issue (or outdate) sterile culture. Bacterial culture surveillance of PLTs would be expected to save lives and may facilitate an extension in PLT storage.     

Canadian experience with detection of bacterial contamination in apheresis platelets

BACKGROUND: In Canada, both blood suppliers, Héma-Québec (HQ) and Canadian Blood Services (CBS), implemented bacterial testing in apheresis platelets (PLTs) with an automated microbial detection system (BacT/ALERT, bioMérieux). STUDY DESIGN AND METHODS: Validation of the BacT/ALERT Classic and 3D systems involved apheresis PLT spiking with different bacteria at concentrations of 10 and 10(2) colony-forming units per mL. As of February 2006, more than 95 percent of apheresis PLTs were screened for bacterial contamination at HQ and CBS. Between 3.5 and 10 mL of PLTs is inoculated into BacT/ALERT aerobic culture bottles followed by incubation for a maximum of 7 days. RESULTS: During the validation studies, all bacteria were detected at all concentrations and volumes tested. Upon implementation of bacterial screening, the percentage of initial positive samples at CBS and HQ was 0.09 and 0.07 percent, respectively. The rate of indeterminate cultures was significantly higher at CBS than at HQ, whereas the rates for true-positive, false-positive, and false-negative results did not differ significantly. Six confirmed-positive cultures, including three coagulase-negative staphylococci and three Enterobacteriaceae species, were detected and PLT units contaminated with these bacteria were not transfused. The rate of true-positive cultures was significantly lower than that reported by other blood operators. Unfortunately, failed detection of two contaminated units resulted in septic transfusion reactions. CONCLUSION: Bacterial screening of apheresis PLTs in Canada was successfully implemented, and transfusion of contaminated units was prevented. Rapid bacterial detection systems that could be used before transfusion, however, may further reduce the risk of transfusion reactions.     

Detection of bacterial contamination in apheresis platelet products: American Red Cross experience, 2004

BACKGROUND: Routine quality control (QC) testing for bacterial contamination in apheresis platelet (PLT) products was implemented in all 36 regional blood centers of the American Red Cross in March 2004. STUDY DESIGN AND METHODS: PLT samples were cultured under aerobic conditions until the end of the product shelf life or when a positive reaction was indicated. To confirm the initial positive reaction, a new sample was taken from the unit for reculturing. All positive culture bottles were referred for bacterial isolation and identification. Bacterial testing data along with apheresis PLT collection information were collected for analysis. Reports and investigations of potential septic reactions to apheresis PLTs were reviewed. RESULTS: In the first 10 months of bacterial testing, 226 of 350,658 collections tested initially positive. Sixty-eight were confirmed on resampling to be bacterially contaminated for an overall confirmed-positive rate of 0.019 percent or 1 in 5157. Staphylococcus spp. (47.1%) and Streptococcus spp. (26.5%) were the most frequently isolated bacteria; Gram-negative bacteria accounted for 17.6 percent of the confirmed-positive products. Of the 354 apheresis PLT products derived from all 226 initial test-positive cases, 38 (10.7%) were transfused by the time the initial positive reaction was indicated. None of these transfused products, however, had a confirmed-positive bacterial screen and no patient who had been transfused with an unconfirmed-positive product had evidence of a septic transfusion reaction. Three high-probability septic transfusion reactions to screened, negative components were identified. In all three cases, a coagulase-negative Staphylococcus was implicated. CONCLUSION: Our experience demonstrates that bacterial testing of apheresis PLT products as a QC measure was efficiently implemented throughout the American Red Cross system and that this new procedure has been effective in identifying and preventing the transfusion of many, although not all, bacterially contaminated PLT units.     

Detection of bacterial contamination of apheresis platelets in a Chinese Blood Center

Bacterial contamination of platelets is considered as the most frequent infectious risk of transfusion. The prevalence of bacterial contamination has been reported and varied considerably in different countries, but the data for bacterial contamination of platelets in China are rarely reported. Eight thousand apheresis platelet concentrates (PCs) were analysed by aerobic and anaerobic cultures. Ten millilitres of PCs were inoculated into aerobic and anaerobic bottles (5 mL each), followed by the incubation for a maximum of 7 days. A new sample was taken from the unit for reculturing in order to confirm the initial positive reaction. All positive culture bottles were referred for bacterial isolation and identification. Twenty one cultures (0.26%) were flagged as positive in initial culture. Five cultures (0.06%) were confirmed as true positive and nine cultures (0.11%) were confirmed as indeterminate in reculture. A bacterium from skin flora ( Propionibacterium spp.) was the most prevalent contaminant. Mean time to initial positive culture from start of incubation was 22.1 h for confirmed positive units and 97.3 h for indeterminate units. Most PC units had already been issued by the time of initial positive culture with a 'negative-to-date' issued strategy. There is a risk of bacterial contamination of PCs in China. Implementing bacterial screening of platelets could reduce the risk of septic reaction and fatalities due to transfusion of bacterially contaminated platelets. However, bacterial contamination PCs can still be transfused due to the delay until a positive signal in the culture system.     

Allergic agonists in apheresis platelet products are associated with allergic transfusion reactions

BACKGROUND: The mechanisms that underlie allergic transfusion reactions (ATRs) are not well characterized, but likely involve recipient, donor, and product factors. To assess product factors associated with ATRs, we investigated candidate mediators in apheresis platelet (PLT) products associated with ATRs and controls. STUDY DESIGN AND METHODS: Using bead‐based and standard enzyme‐linked immunosorbent assays, we tested supernatants from 20 consecutive apheresis PLT transfusions associated with ATRs and 30 control products for concentrations of mediators in three categories: acute inflammatory mediators, direct agonists of basophils and mast cells, and growth and/or priming factors of basophils and mast cells. RESULTS: Median concentrations of the direct allergic agonists C5a, brain‐derived neurotrophic factor (BDNF), and CCL5 (RANTES) were 16.6, 41.8, and 13.9% higher, respectively, in the supernatant of apheresis PLT products that were most strongly associated with ATRs (p < 0.05 for each mediator). Other direct agonists (macrophage inflammatory protein‐1α, monocyte chemotactic protein‐1, eotaxin‐1, interleukin‐8) were similar between groups. Concentrations of acute inflammatory mediators and basophil growth and/or priming factors were also similar between groups (p > 0.2 for all associations). CONCLUSION: The allergic agonists C5a, BDNF, and CCL5 may be mediators of ATRs in apheresis PLT products. Acute inflammatory proteins and basophil and/or mast cell growth and priming factors do not appear to be associated with apheresis PLT products that cause ATRs.     

Evaluation of platelet transfusion triggers in a tertiary-care hospital

BACKGROUND: Our 1100-bed referral hospital uses approximately 12,000 units of random-donor platelets (PLTs) and 1,900 units of single-donor apheresis PLTs per year with a mean of 23 percent outdating. An analysis of patterns of utilization has been undertaken to evaluate practice. STUDY DESIGN AND METHODS: Over a 9-month period, data were collected on a total of 1682 transfusion episodes in 464 patients. When the pretransfusion count was greater than 10 x 10(9) per L an attempt was made to identify the specific indications for PLT transfusions such as bleeding. RESULTS: The majority (78%) of PLTs were transfused when the counts were above 10 x 10(9) per L. The mean pretransfusion counts for different services were: bone marrow transplant (BMT) 17.4 x 10(9) per L, hematology-oncology 14.6 x 10(9) per L, the Heart Institute 3 x 10(9) per L, and other services 36 x 10(9) per L. The percentage of transfusions given to patients with a count greater than 10 x 10(9) per L varied by service with 79 percent in BMT, 60 percent in hematology and oncology, 98 percent at the Heart Institute, and 81 percent in other services. Routine monitoring of counts shows a mean increment of 10.2 x 10(9) per L per transfusion. One hour posttransfusion counts, 24-hour posttransfustion counts, and documentation of clinical justification for transfusions was often not available. CONCLUSIONS: The data show that most patients who receive PLTs have pretransfusion counts of more than 10 x 10(9) per L and more than one-third have pretransfusion counts of greater than 20 x 10(9) per L. The medical literature supports prophylactic PLT transfusion based solely on the count when the PLT number is 10 x 10(9) per L or less. Above this level additional justification is needed although there are different points of view concerning the appropriate triggers. Our data suggest that there is a need for clear hospital transfusion guidelines and ongoing monitoring of PLT use.     

Risk management in transfusion medicine: a hospital transfusion service perspective

The hospital transfusion service has always been at the heart of the blood component therapy chain. It has had the multiple roles of not only maintaining an inventory of a wide range of blood components, monitoring their storage conditions and ensuring compatibility when appropriate, but also being the source of expertise in transfusion medicine, and attempting to follow up any adverse consequences of transfusion. Hospital transfusion medicine has been seen essentially as a scientific and technical specialty with a minimal component of medical input. This is now changing and transfusion medicine is becoming an all embracing specialty where the hospital transfusion service still remains at the heart of transfusion medicine, but a much higher level of understanding is necessary at the clinical and consumer level.     

Problem of bacterial contamination in platelet concentrates

Bacterial contamination of blood is being recognized more frequently now and is one of the serious complications of transfusion. Use of integrally attached collection systems and strict standards for skin preparation, collection and storage of blood and components have reduced but not eliminated the risk of bacterial contamination. As bacteraemia may be part of acute or sub acute infections, strict donor selection is warranted. The longer the storage time, the greater is the number of organisms and amount of endotoxin present in the unit and associated with transfusion reactions. Importance of haemovigilance system and awareness among clinicians on the potential complications will go a long way in reducing patient morbidity. New approaches for detection of bacterial contamination, pathogen reduction and developments in the field of platelet biology will increase blood safety.     

Periodic alternating interface positioning to lower WBC contamination of apheresis platelet concentrates: a multicenter evaluation

BACKGROUND: A new software version of a cell separator (AS TEC 204, Fresenius) providing WBC-reduced single-donor plateletpheresis concentrates was tested. STUDY DESIGN AND METHODS: Dual-needle apheresis procedures (n = 621) were performed in three centers, using either fixed interface positioning (FIP) or periodic alternating interface positioning (PAIP). The other separation parameters (e.g., anticoagulant:whole-blood ratio, and blood flow) were set individually. All platelet concentrates were evaluated for platelet yields and contaminating WBCs. RESULTS: The introduction of the PAIP resulted in a significant (p<0.001) reduction in contaminating WBCs (median, 30,000) from the numbers seen with FIP (median, 2,300,000) while maintaining the separation efficacy (47%) and separation time. Ninety-eight percent of all concentrates contained less than 5 x 10(6) WBCs per concentrate and 92 percent contained less than 1 x 10(6). CONCLUSION: Plateletpheresis using the AS TEC 204 cell separator with PAIP is a valid alternative to WBC reduction by filtration. It may provide WBC-reduced platelet concentrates without the additional cost of filters. However, the reliability of the WBC reduction is not yet advanced enough that PAIP can be employed without any monitoring of the end product.     

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

Background: The residual risk for bacterial contamination in blood components especially in platelets is one to two orders of magnitude higher than for transfusion relevant viral infections. The majority of all bacterial transmitted fatalities occurred at the end of platelet shelf life. Therefore, the maximum shelf life of platelet concentrates (PC) was reduced to 4 days after blood donation in Germany in 2008. Methods: A new continuous non‐invasive bacterial detection method was developed by O₂ measurements in the platelet fluids and tested with 10 transfusion relevant bacteria species. Results: The bacterial concentration at the time point of a positive signal of PreSense O₂ ranged between 10² and 10⁵ CFU mL^?1. Harmful transfusion‐transmitted bacterial infection would have probably been prevented by this novel technology. Only strict anaerobic bacteria strains like Clostridium perfringens were not detected within the study period of 72 h. Conclusions: The described non‐invasive bacterial detection method represents a new approach to prevent transmission of bacterial infection in platelets. The method is characterised by the advantage that all investigations can be performed until right up to the time of transfusion, and therefore, reduce the risk for sample errors to a minimum.     

Platelet bacterial contamination and the use of a chemiluminescence- linked universal bacterial ribosomal RNA gene probe

BACKGROUND: Currently, the maximum outdate for platelets is 5 days, because of the increasing chance of bacterial growth over time. Various methods for rapid detection of bacterial contamination of blood components have been described, with mixed results and no general acceptance. A recently described, molecular biologic approach for the detection of bacterial contamination involves a chemiluminescence- linked universal DNA bacterial probe to a highly conserved bacterial region of ribosomal RNA (rRNA). STUDY DESIGN AND METHODS: A multicenter trial of a chemiluminescence-linked universal bacterial rRNA probe for the detection of bacterial contamination in platelet concentrates is described. At each of five sites, platelet concentrates (no older than 1 day from date of phlebotomy) were inoculated in triplicate with isolates of four bacterial species (Pseudomonas aeruginosa, Bacillus cereus, Staphylococcus epidermidis, and Staphylococcus aureus) to a final concentration of 10 to 50 colony-forming units (CFUs) per mL and in triplicate to a final concentration of 1000 CFUs per mL. At one site, an additional 6 platelet concentrates were inoculated with sterile saline to serve as controls. Inoculated units were then subjected periodically to quantitative cultures and probe analyses. A total of 126 platelet concentrates were studied over a period of 7 days (120 inoculated with bacteria and 6 with sterile saline). RESULTS: This assay was, in some cases, able to detect S. aureus bacterial contamination in the range of 100 to 1000 CFUs per mL; the majority of samples (B. cereus, P. aeruginosa, S. aureus, and S. epidermidis) with contamination exceeding 10(4) CFUs per mL; and all samples with contamination of 2.1 × 10(5) CFUs per mL or greater. Increasing the sample size from the recommended 0.4 mL to 1.0 mL resulted in an unacceptable loss of specificity (83.3%). CONCLUSION: The routine use of this assay would be expected to result in a decreased risk of septic platelet transfusion reactions and could lead to a lengthening of the current 5 day storage period for platelets. Further, the pooling of random-donor platelet concentrates before storage instead of immediately before transfusion may be possible if this rRNA probe is employed to detect bacteria in the pool.     

利用医院信息系统再造门诊就诊输液流程的实践

目的:探讨优化门诊患者就诊输液流程的途径和方法,提升门诊服务质量和管理水平。方法:借助医院数字化信息系统平台优势,进行一系列就诊至输液整体流程的再造,包括建立电子诊疗卡就诊交费流程、全程计算机传输处方流程、传送带传输药物流程、输液室电子显示及呼叫流程等。结果:通过信息系统进行流程再造后,门诊患者就诊至输液各环节等候时间、护理人员各项操作用时、护患双方对流程满意度与实施流程再造前对比,两组有统计学差异(P<0.05)。结论:利用信息化平台进行输液流程再造,可以有效解决传统门诊患者就诊输液流程中的问题和弊端,是实施门诊流程再造的有效途径。