Effect of Safety Measures on Bacterial Contamination Rates of Blood Components in Germany.

SUMMARY: Requirements for bacterial testing of blood components on a defined quantity as part of routine quality control were introduced in Germany by the National Advisory Committee Blood of the German Federal Ministry of Health in 1997. The philosophy was to establish standardized methods for bacterial testing. Numerous measures to reduce the risk of bacterial contamination were implemented into the blood donation and manufacturing processes between 1999 and 2002. German Blood establishments performed culture-based bacterial testing on random samples of platelet concentrates (PCs), red blood cells (RBCs) and fresh frozen plasma (FFP) and reported data out of the production periods 1998, 2001 and 2005/2006. While the bacterial contamination rate of apheresis PCs remained nearly unchanged, it decreased by 70% for pooled PCs to a rate of 0.158% in the last observation period. Leukocyte-depleted RBCs with diversion of the initial blood volume showed a contamination rate of 0.029% which is significantly lower than that of RBCs without leukocyte depletion and diversion (0.157%). The contamination rate of plasma decreased by 80%. Preventive measures resulted in a significant reduction of bacterial contamination of blood components. Long-term monitoring with standardized methods for bacteria testing supports evaluation of the cumulative effect of contamination reducing measures.

Screening of platelet concentrates for bacterial contamination: spectrum of bacteria detected, proportion of transfused units, and clinical follow-up.

Screening of platelet concentrates (PCs) for bacterial contamination with cultivation methods is carried out as a routine procedure in some countries. The aim is to prevent the transfusion of contaminated PCs. The German Evaluation of Regular Monitoring Study Group conducted a prospective multicenter study on 52,243 PCs to investigate the prevalence of bacteria (BacT/ALERT, bioMerieux). This study describes the detected bacterial spectrum, the proportion of PCs with a positive test result that had been transfused, and the results of the clinical follow-up. One hundred thirteen (67%) of 169 potentially or confirmed positive units had already been transfused at the time of the first positive signal. The transfusion of units contaminated by Staphylococcus aureus, Serratia marcescens, and 73% of the units contaminated with Staphylococcus epidermidis, Staphylococcus capitis, or Staphylococcus saccharolyticus was prevented. In contrast, 85% of units with Propionibacterium acnes were transfused. A clonal relationship of the isolates from the pooled PCs and from the associated red blood cell concentrates was found in all investigated cases. The follow-up revealed six febrile reactions to culture-positive PCs not classified as transfusion reaction (TRs) by treating physicians. This demonstrates the importance of hemovigilance. Serious septic reactions due to Klebsiella pneumoniae in two units of one apheresis PC that had tested false-negative were reported; one had a fatal outcome. Culture systems reduce the risk of transfusion of contaminated PCs but cannot guarantee sterility. Physicians must be aware of bacterial contamination of PCs as a potential cause of TRs and must report all adverse events.

Bacterial screening of platelet concentrates on day 2 and 3 with flow cytometry: the optimal sampling time point?

BACKGROUND: There is growing concern on the residual risk of bacterial contamination of platelet concentrates in Germany, despite the reduction of the shelf-life of these concentrates and the introduction of bacterial screening. In this study, the applicability of the BactiFlow flow cytometric assay for bacterial screening of platelet concentrates on day 2 or 3 of their shelf-life was assessed in two German blood services. The results were used to evaluate currently implemented or newly discussed screening strategies. MATERIALS AND METHODS: Two thousand and ten apheresis platelet concentrates were tested on day 2 or day 3 after donation using BactiFlow flow cytometry. Reactive samples were confirmed by the BacT/Alert culture system. RESULTS: Twenty-four of the 2,100 platelet concentrates tested were reactive in the first test by BactiFlow. Of these 24 platelet concentrates, 12 were false-positive and the other 12 were initially reactive. None of the microbiological cultures of the initially reactive samples was positive. Parallel examination of 1,026 platelet concentrates by culture revealed three positive platelet concentrates with bacteria detected only in the anaerobic culture bottle and identified as Staphylococcus species. Two platelet concentrates were confirmed positive for Staphylcoccus epidermidis by culture. Retrospective analysis of the growth kinetics of the bacteria indicated that the bacterial titres were most likely below the diagnostic sensitivity of the BactiFlow assay (<300 CFU/mL) and probably had no transfusion relevance. CONCLUSIONS: The BactiFlow assay is very convenient for bacterial screening of platelet concentrates independently of the testing day and the screening strategy. Although the optimal screening strategy could not be defined, this study provides further data to help achieve this goal.

Incidence of bacterial transmission and transfusion reactions by blood components.

Successful reduction of the risk of viral transmission via blood components has focused attention on the risk of transfusion-associated bacterial sepsis. The incidence of transfusion reactions due to bacteria is currently estimated at between 1 per 100,000 and 1 per 1,000,000 units in the case of packed red blood cells and between 1 per 900 and 1 per 100,000 units in the case of platelet concentrates. For autologous transfusion, only isolated case reports are available which do not permit a quantitative risk assessment. No reliable data on the risk of morbidity and mortality due to transfusion-associated bacterial infection are available for Germany at present. As platelet concentrates provide more favourable conditions for bacterial growth by virtue of being stored at room temperature, these blood components are thought to bear a considerably greater risk of bacterial contamination than red blood cells. The rate of contamination of platelet concentrates is cited at between 0.02% and 1.2%, depending on the production and bacterial culture techniques used, whereas the rate for packed red blood cells is between 0.1% and 0.2%. Risk reduction strategies include careful selection of blood donors, optimisation of donation and production techniques, and detection of bacteria in samples of blood components prior to transfusion. Also of importance for patient safety are quality assurance measures in the preparation for transfusion, in measures of patient monitoring, and investigation of transfusion reactions.

Bacterial contamination of platelet concentrates: results of a prospective multicenter study comparing pooled whole blood-derived platelets and apheresis platelets.

BACKGROUND: The GERMS Group initiated a prospective multicenter study to assess prevalence and nature of bacterial contamination of pooled buffy-coat platelet concentrates (PPCs) and apheresis platelet concentrates (APCs) by routine screening with a bacterial culture system. STUDY DESIGN AND METHODS: In nine centers overall, 52,243 platelet (PLT) concentrates (15,198 APCs, 37,045 PPCs) were analyzed by aerobic and anaerobic cultures (BacT/ALERT, bioMérieux). RESULTS: In 135 PLT concentrates (PCs; 0.26%), bacteria could be identified in the first culture (0.4% for APCs vs. 0.2% for PPCs; p < 0.001). In 37 (0.07%) of these PC units, the same bacteria strain could be identified in a second culture from the sample bag and/or the PC unit. The rate of confirmed-positive units did not differ significantly between APC (0.09%; 1/1169) and PPC units (0.06%; 1/1544). Bacteria from skin flora (Propionibacterium acnes, Staphylococcus epidermidis) were the most prevalent contaminants. Median times to first positive culture from start of incubation were 0.7 and 3.7 days in aerobic and anaerobic cultures for confirmed-positive units. With a "negative-to-date" issue strategy, most PC units (55%) had already been issued by time of the first positive culture. CONCLUSION: The rate of confirmed bacterial contamination of PC units was low. Nevertheless, clinicians must be aware of this risk. The risk of bacterial contamination does not warrant universal preference of APCs. It must be questioned whether routine bacterial screening by a culture method can sufficiently prevent contaminated products from being transfused due to the delay until a positive signal in the culture system and due to false-negative results.