Establishment of a proficiency panel for an external quality assessment programme for the detection of bacterial contamination in platelet concentrates using rapid and cultural detection methods.

BACKGROUND: Platelet concentrates (PCs) are the main focus regarding the residual risk of transfusion-transmitted bacterial infections. Rapid screening methods for bacterial detection in platelets have been optimized over the last decade, but their external evaluation represents a complicated process. We developed a new type of proficiency panel for bacterial detection in PCs using currently available screening methods (especially rapid methods) suitable for external quality assessment programmes (EQAP). METHODS: PC samples were inoculated with different bacteria at two concentrations (10E+03 CFU/ml, 10E+05 CFU/ml) and stored under temperature-controlled conditions (1-5 days). Bacterial growth was further prevented by the addition of 0-20 µg/ml cotrimoxazole. Samples were analysed prior to and after storage using rapid detection methods (Bactiflow (BF), bacteria-generic NAT) and cultural methods to determine the influence of storage and antibiotic treatment on bacterial counts and the result outcome. A pilot EQAP was performed with four participants. RESULTS: Testing under the evaluated conditions demonstrated that bacterial counts remained constant prior to and after storage. The supplementation of 10 µg/ml cotrimoxazole did not influence bacterial detection using the two rapid detection methods BF and NAT. Furthermore, the detection of bacteria using cultural methods is still possible despite of antibiotic supplementation. The pilot EQAP confirmed these results. A storage time of up to 3 days proved practicable, showing no considerable influence on bacterial count and outcome of test results. CONCLUSION: The established proficiency panel provided PC matrix-conform samples with stabilized bacterial counts which can be analysed in parallel by rapid and cultural detection methods.

Routine bacterial screening of platelet concentrates by flow cytometry and its impact on product safety and supply.

BACKGROUND AND OBJECTIVES: Bacterial contamination represents the major infectious hazard associated with transfusion of platelet concentrates (PCs). As bacterial screening of PCs is not mandatory in Germany, the BactiFlow flow cytometry test has been introduced as a rapid detection method to increase product safety. MATERIALS AND METHODS: During a period of 25 months, a total of 34 631 PCs (26 411 pooled and 8220 apheresis-derived PCs) were tested at the end of day 3 of their shelf life using the BactiFlow system. PCs initially reactive in BactiFlow testing and expired PCs not reactive in BactiFlow on day 3 were also investigated by the BacT/ALERT system and by microbiological cultivation in order to identify the contaminating bacterial species and to confirm reactive BactiFlow results. RESULTS: Two hundred and twenty-eight PCs (0.7%) had an initially reactive result, 24 of them remained reactive in a second test run. Out of these reproducible reactive BactiFlow results, 12 could not be verified by parallel BacT/ALERT culturing, resulting in a confirmed false-positive rate of 0.03%. The bacterial species were identified as S. aureus, S. epidermidis, S. dysgalactiae ssp. equisimilis and B. cereus. In 10 out of 9017 expired PCs (0.11%), a confirmed-positive result was obtained in the BacT/ALERT system which had a negative result in the BactiFlow system. CONCLUSION: Testing of PCs by BactiFlow was successfully implemented in our blood donation service and proved sufficient as a rapid and reliable screening method. False reactive results are in an acceptable range since the transfusion of 12 bacterially contaminated PCs was prevented.

Detection of bacterial contamination in platelet concentrates by a sensitive flow cytometric assay (BactiFlow): a multicentre validation study.

BACKGROUND: Bacterial contamination of platelet concentrates (PCs) still represents an ongoing risk. As a result of septic complications, particularly observed with older PCs, the shelf life of PCs has been reduced in Germany to 4 days. In this study, bacterial screening of PCs by BactiFlow (BF) flow cytometry was introduced in three German blood services to evaluate the robustness and applicability of the assay. Results were used to discuss the potential for the extension of PC shelf life to 5 days. STUDY DESIGN AND METHODS: A total of 1956 PCs were tested on days 4 or 5+ after PC production using the BF, whereas the BacT/Alert culture system served as reference method. RESULTS: Two PCs were confirmed positive by culture only and were identified as Propionibacterium acnes and Staphylococcus species. Two PCs were confirmed positive for Streptococcus mitis by BF and culture. Additionally, two PCs were culture-positive only in one culture bottle (aerobic: S. mitis and anaerobic: S. hominis). Retrospective analysis of bacterial growth kinetics provide the indication that corresponding bacterial titres were most likely below the BF analytical detection limit (<150 CFU mL(-1) ) and had probably no transfusion relevance. All remaining specimens were tested negative. CONCLUSIONS: Testing of PCs by BF was successfully implemented. The BF proved sufficient as a rapid screening method to improve PC safety. This study further provides data supporting the extension of PC shelf life to 5 days after negative BF testing on day 4.

Inter-laboratory comparison of different rapid methods for the detection of bacterial contamination in platelet concentrates.

BACKGROUND: Bacterial contamination of platelet concentrates still represents a major risk in transfusion medicine, and a variety of screening methods have been available to improve the safety of PCs. In the present study, the analytical quality of three different rapid screening methods (BactiFlow flow cytometry, Pan Genera Detection Assay, 23S rRNA RT-PCR) was evaluated in an inter-laboratory comparison in three different German blood services. METHODS: Samples were inoculated with different bacteria [Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli (two strains), Klebsiella pneumoniae (two strains), Enterobacter aerogenes (one strain), Serratia marcescens (one strain)] at different counts (4·5 × 10(3) -4·5 × 10(8) CFU/ml) alternating with negative samples in one transfusion facility. Samples were blinded with a random order for each screening method, shipped to partners and analysed immediately after receipt with different rapid screening methods. RESULTS: The inter-laboratory comparison revealed that the BactiFlow assay and 23S rRNA RT-PCR-screening detected all samples correctly (positive: 12/12, negative: 8/8). The Pan Genera Detection Assay test detected only four of the positive samples. Four of the non-detected positive samples were below the assay's detection limit. Another four inoculated samples with comparatively high bacteria counts were detected false negative (E. coli (two strains): 9·87 × 10(5) and 2·10 × 10(7) CFU/ml, respectively, K. pneumoniae: 4·79 × 10(6) CFU/ml, S. aureus: 6·03 × 10(5) CFU/ml). All rapid screening methods revealed no false-positive results. CONCLUSIONS: Both BactiFlow and 23S rRNA RT-PCR demonstrated a high sensitivity to detecting bacterial contamination in PCs. The Pan Genera Detection Assay had some shortcomings regarding sensitivity, especially for the detection of Gram-negative strains.

Serum antibodies to conformational and linear epitopes of myelin oligodendrocyte glycoprotein are not elevated in the preclinical phase of multiple sclerosis.

BACKGROUND: The proposed predictive value of serum anti-myelin antibodies for the development of multiple sclerosis after a first clinically isolated syndrome was recently challenged. OBJECTIVE: To investigate myelin autoantibodies before first disease manifestation using different detection methods. METHODS: Patients with multiple sclerosis who had donated blood at a time prior to development of clinically isolated syndrome were identified via the German National Multiple Sclerosis Society. Control sera were obtained from age- and gender-matched blood donors. IgG-/IgM-antibodies against the extracellular part of native, cell surface-expressed myelin oligodendrocyte glycoprotein were detected by flow cytometry. Antibodies against linear epitopes were identified by immunoblot using recombinant myelin oligodendrocyte glycoprotein (aa1-125) and human myelin basic protein preparations. RESULTS: Fifty eight serum samples from 25 patients covering an interval of 7.3 years-2 months prior to disease onset were available. Longitudinal investigations were performed in 19 patients (2-14 samples per patient, 7 years-2 months prior to disease onset). No significant differences in the prevalence or titres of anti-myelin antibodies were detected between sera of preclinical individuals and healthy donors by either flow cytometry or immunoblot. There was no correlation between interval before clinically isolated syndrome and autoantibody status. Occurrence of antibodies was not associated with symptomatology/severity of clinically isolated syndrome. CONCLUSION: Neither anti-myelin autoantibodies against cell surface-expressed native myelin oligodendrocyte glycoprotein nor against linear epitopes have a predictive or discriminative role during the preclinical disease phase for developing clinically isolated syndrome or multiple sclerosis later in life.

Blood donor screening with cobas s 201/cobas TaqScreen MPX under routine conditions at German Red Cross institutes.

BACKGROUND: In 1997 the German Red Cross (GRC) blood donor services introduced mini-pool nucleic acid testing (NAT) for human immunodeficiency virus (HIV)-1, hepatitis C virus (HCV) and hepatitis B virus (HBV) to increase blood safety. With the new cobas s 201/cobas TaqScreen MPX, a fully automated extraction method and a multiplex amplification system specifically adapted to the needs of blood donation services is available. METHODS: The cobas s 201 system was evaluated at the GRC BTS locations Hagen, Springe and Frankfurt. In phase A, the analytical sensitivity for the detection of HBV, HCV and HIV-1 was investigated and in phase B, at least 60,000 samples at each test site were screened in parallel with the MPX test on s 201 system and the existing routine mini-pool NAT system to compare the diagnostic specificity and the diagnostic sensitivity. RESULTS: Comparable analytical sensitivities in a range of 1.6-3.6 IU/ml, 4.9-10.9 IU/ml and 14.7-26.6 IU/ml for HBV, HCV HIV, respectively, for the MPX test on s 201 system (95% probability based on probit analysis) were determined at all test sites. The diagnostic sensitivity was 99.8% and the diagnostic specificity was 99.85%. CONCLUSIONS: The MPX test on s 201 system is a fully automated NAT system suitable for routine blood donor screening. The analytical sensitivity as well as the diagnostic sensitivity fulfilled all requirements of the Paul Ehrlich Institute for blood donor screening in mini-pools up to 96 donations per pool. A major benefit of the automated NAT system is the reduced personnel time and the extensive complete barcode-controlled process documentation.

Sterility screening of platelet concentrates: questioning the optimal test strategy.

BACKGROUND: Routine bacterial monitoring of apheresis platelet concentrates (APC) and pooled platelet concentrates (PPC) was introduced in two German blood services using culture and real-time reverse transcriptase (RT)-polymerase chain reaction (PCR). The results of testing are reviewed and used to discuss different strategies for detection of bacterial contamination of PCs. STUDY DESIGN AND METHODS: Two thousand three hundred and sixty-two APCs and 1993 PPCs have been tested by real-time RT-PCR and the BacT/Alert automated culturing system using aerobic and anaerobic culture bottles. After standard processing of PCs and storage of 22-24 h at 20-24 degrees C with agitation, samples were taken under aseptic conditions. Reactive culture bottles were confirmed as positive and bacterial isolates were identified by 16S rRNA analysis and biochemical tests. RESULTS: Seventeen of 2362 tested APCs were reactive in culture and one also in RT-PCR. Of these, 13 APCs were identified as initially positive as Staphylococcus warneri (n = 1, positive in aerobic and anaerobic culture), Propionibacterium acnes (n = 12, positive only in anaerobic culture) and four were initially reactive. Two of 1993 PPCs were initially reactive (anaerobic) and two more were confirmed positive (anaerobic) from a repeat culture and identified as P. acnes. All remaining specimens were tested negative. CONCLUSION: Our study demonstrates that the predominant organisms implicated in platelet bacterial contamination are part of the human skin flora. Inoculating blood culture systems and anaerobic cultivation detects these bacteria after approximately 3-7 days when blood products have been transfused. Based on the presented data different screening strategies are discussed.

European multi-centre validation study of NucliSens Extractor in combination with HCV Amplicor 2.0 assay for HCV-NAT screening of plasma pools.

The NucliSens Extractor in combination with the 2.0 version of the Roche Cobas HCV Amplicor test has been validated by five European blood screening laboratories in a multi-centre study. For testing the performance characteristics of this HCV-NAT method, the European Pharmacopoeia validation guidelines were followed. The CLB VQC reference reagents were used for testing robustness and sensitivity. After a technical improvement in the extraction stations, the NucliSens Extractor appeared to be contamination-free as was proved by testing negative controls alternating with samples containing a high HCV-RNA concentration. The Pelicheck HCV-RNA genotype 1 dilution panel was tested 74 times in the five laboratories and an overall 95% detection limit of 80 genome equivalents (geq)/ml was found. In one laboratory the Pelicheck panel was tested in 25 runs and here a 95% detection limit of 32 geq/ml was achieved. In this laboratory the Pelispy HCV-RNA run control samples of 140 geq/ml were consistently picked up in all extractor stations. In addition the laboratories have tested a WHO HCV-RNA genotype 1 standard dilution series 39 times and a Pelicheck HCV-RNA genotype 3 reference panel in 32 test runs. The limiting dilution analysis enabled us to compare the detection efficiency of the NucliSens-Amplicor method for the genoype 1 and genotype 3 isolates and to calibrate the reference reagents against each other. The combined Nuclisens-Amplicor method was found to detect the genotype 3 isolate in the Pelicheck HCV-RNA panels with 2-3 fold lower efficiency than the genotype 1 standard (assuming that the historical calibration of the genotype 3 against the genotype 1 standard is correct). In this study of a single method 1 IU of the WHO HCV-RNA standard was found to be equivalent to 5.1 geq of the VQC HCV-RNA standard (95% confidence intervals 3.1-9.1 geq). To avoid confusion with the use of the CLB VQC reagents we accept the NIBSC collaborative study in which calibration by a variety of methods showed that the Pelispy 380 geq/ml run control is equivalent to 100 IU/ml of the WHO standard. This multi-centre validation study demonstrates that the 95% detection limit of the NucliSens HCV Amplicor method lies far below the detection limits required by the international regulatory bodies.

PCR for HBV, HCV and HIV-1 experiences and first results from a routine screening programme in a large blood transfusion service.

We adapted the PCR method to screen up to 3000 blood donations per day for hepatitis B, hepatitis C and HIV-1 virus contamination. Up to 600 aliquots (average 418 donations) are pooled by using an automatic sample processor with disposable tips (validated to avoid contamination) taken from blood donations which are serologically negative and free for clinical usage according to federal regulations. In the case of a positive PCR pool result the viraemic donation is identified by two additional PCR pools testing steps with smaller pool sizes. All of the steps are supported by electronic data processing. After virus concentration by ultracentrifugation, and in the case of HCV and HIV-1 an additional reverse transcription step, PCR amplifications are performed. PCRs are done for each virus in two genomic regions. Laser-induced detection after PAGE and computer-analysis are used to identify the amplification products. Using this validated methodology routine we have checked 428 896 donations up to the end of August 1996. During this survey we found at least 24 viruses-containing donations which were negative in corresponding serological tests and would have been transfused (2 HBV-, 22 HCV-, 0 HIV-1 -containing donations). It seems possible for large transfusion centres to shorten the diagnostic window periods with our PCR-methodology with acceptable costs (15 DM per donation for all three viruses including logistics, developments and investments).

[Routine PCR screening for HBV, HCV and HIV-I genome in a large blood donation services--experiences and initial results]. / PCR-Routine-Screening auf HBV-, HCV- und HIV-I-Genom in einem grossen Blutspendedienst--Erfahrungen und erste Ergebnisse.

We adapted the PCR method to screen up to 3,000 blood donations per day for HBV, HCV, and HIV-1 contamination. Concerning logistics: The first step is the generation of 3 identical microtiter plates (PT) by using the self-validated automatic sample processor with disposable tips. Using the first PT, we pooled up to 600 aliquots taken from blood donations which are serological negative and free for clinical usage according to actual federal regulations. In the case of a positive PCR pool result the viremic donation is identified by 2 additional PCR pool testing steps with smaller pool sizes using the second and third PT. All described steps are supported by electronic data processing. The PCR-method: After virus concentration by ultracentrifugation and--in case of HCV and HIV-1--additional reverse transcription PCR-amplifications were performed. PCR in two genomic regions are done for each virus. Laser-induced fluorescence detection after polyacrylamide gel electrophoresis and computer analysis were used to check the amplification products. Using this approach, a virus-containing donation can be detected in up to 599 negative samples with following sensitivity: HBV and HIV-1, 1,000-1,500 genome equivalents/ml; HCV, 2,000-2,500 genome equivalents/ml, thus sensitivity being in the range of commercial available PCR kits when testing nonpooled samples. The sensitivity was validated by using national and international available standards with known virus genome concentrations. All processing steps are checked using different controls such as, e.g., negative, positive, premix controls, reporter virus, inhibition controls. Routinely employing this validated methodology, we investigated 327,013 donations until the end of June 1996. During this survey, we found at least 16 virus-containing donations which are negative in corresponding serological tests and would have been transfused (4 HBV-, 13 HCV-, 0 HIV-1-containing donations), including one later seroconversion for HBV and one for HCV. Using our adapted PCR-methodology, it seems possible to shorten the diagnostic window periods with acceptable costs for large transfusion centers (15 DM per donation for all 3 viruses including all steps and investments). Therefore, PCR seems to become a new method of choice to prevent transfusion transmitted infections.

[Sensitivity studies on the demonstration of HIV-1 particles using RT HIV-1 PCR in pooled plasma before virus inactivation]. / Sensitivitätsstudien zum Nachweis von HIV-1-Partikeln mittels RT-HIV-1-PCR im Poolplasma vor Virusinaktivierung.

The goal of this study was the establishment of a reverse-transcription polymerase chain reaction (PCR) test and the evaluation of its sensitivity to detect an HIV-1 contamination in pooled plasma samples prior to the solvent-detergent (SD) inactivation procedure. Pooled plasma samples were spiked with known concentrations (1,000-0.1 TCID50/ml) of HIV-1, originated from tissue culture supernatants. Unspiked plasma samples were used as negative controls. After reverse transcription, a PCR in 4 different HIV-gene regions (gag, pol, env, ltr) followed by a hybridisation with specific probes was done. The achieved sensitivity in 3 tests (pol. gag, ltr) was 0.1 TCID50/ml and 1.0 TCID50/ml in the env-PCR system. It was shown in previous studies that by inactivation of pooled plasma with the SD technique a reduction of HIV-1 infectivity greater than 10(6) is achieved. The combination of PCR testing and the SD inactivation procedure makes it possible for the first time to define the maximum amount of contaminating HIV-1 in case of a negative PCR result. According to this procedure, the residual HIV-1 load of virus-inactivated plasma would not exceed 1 TCID50 per 1,000 litres at worst.