Tamimount Mohammadi

Sanquin Blood Supply Foundation, Amsterdamo, North Holland, Netherlands

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Publications (10)30.85 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Although blood component transfusion is currently regarded as safe, adverse events may occur in recipients of these products. Among those, blood borne viral, bacterial and parasitic infections are best known. For detection of bacterial contamination in platelet concentrates various methods are available or under investigation. One of these methods, real-time polymerase chain reaction (PCR) with particular focus on real-time 16S rDNA detection, will be discussed in this review.
    Clinical Chemistry and Laboratory Medicine 02/2008; 46(7):954-62. · 3.01 Impact Factor
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    ABSTRACT: Although there have been major improvements over the past few decades in detection methods for blood-borne infectious agents, platelet concentrates are still responsible for most cases of transfusion-transmitted bacterial infections. To date, real-time PCR is an indispensable tool in diagnostic laboratories to detect pathogens in a variety of biological samples. In this article, the applications of this powerful technique in the screening of platelet concentrates for bacterial contamination are discussed. Next to pathogen-specific (real-time) PCR assays, particular attention is directed to the recently developed 16S rDNA real-time PCR. This assay has been proven as a convenient way to detect bacterial contamination of platelet concentrates. The assay is sensitive and enables rapid detection of low initial numbers of bacteria in platelet concentrates. The short turnaround time of this assay allows high-throughput screening and reduction of the risk of transfusion of bacterially contaminated units. As with every method, real-time PCR has its advantages and disadvantages. These and especially limitations inherent to generation of false-positive or -negative results are emphasized. The universal nature of detection of the assay may be suitable for generalized bacterial screening of other blood components, such as red blood cells and plasma. Therefore, it is necessary to adapt and optimize detection in red blood cells and plasma with real-time PCR. Further sophistication, miniaturization and standardization of extraction and amplification methods should improve the total performance and robustness of the assay. Hence, real-time PCR is an attractive method in development as a more rapid screening test than currently used culture methods to detect bacterial contamination in blood components.
    Expert Review of Molecular Diagnostics 12/2006; 6(6):865-72. · 4.09 Impact Factor
  • Laboratoriumsmedizin-journal of Laboratory Medicine - LABORATORIUMSMEDIZIN. 01/2006; 30(6):402-411.
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    ABSTRACT: Propionibacterium acnes is implicated in most cases of bacterial contamination of platelet concentrates (PCs). To determine the source of contamination, amplified-fragment length polymorphism (AFLP) analysis was applied. This DNA fingerprinting technique was used to study the molecular relationship of 44 isolates derived from 22 PCs and 22 corresponding red blood cells concentrates (RBCs) from the same whole blood donations. The AFLP results together with sequencing analysis of the 1,200 bp of the 16S ribosomal RNA gene revealed the existence of three main groups: two groups (groups 2 and 3) (55%) consisted of isolates that did not originate from skin flora and another group (group 1) (45%) comprised bacteria belonging to the skin flora. This latter group showed complete homology with reference strains of P. acnes. Therefore these isolates can be considered as P. acnes strains. In contrast, contaminants from groups 2 and 3 were shown to be molecularly unrelated to the P. acnes found on the skin surface. The AFLP is reproducible and gave invaluable information about the nature of Propionibacteria contaminating PCs. To gain more insights into the source of contamination, this technique could be exploited in further studies to determine the molecular relationship of different bacteria commonly found in blood products.
    British Journal of Haematology 12/2005; 131(3):403-9. · 4.94 Impact Factor
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    ABSTRACT: A universal quantitative real-time polymerase chain reaction (PCR), based on bacterial 16S rDNA, to detect bacterial contamination of platelet concentrates (PCs), was developed previously and compared with automated culturing. In the present study, this real-time PCR method was evaluated to determine the optimal sampling time for screening of bacterial contamination in PCs. Routinely prepared PCs were spiked with suspensions of Escherichia coli, Bacillus cereus, Staphylococcus epidermidis, Pseudomonas aeruginosa and Propionibacterium acnes to 1, 10 and 100 colony-forming units (CFU)/ml and stored at room temperature for 7 days. The presence of bacteria in these PCs was monitored by quantitative real-time PCR. As a reference method (additional control), BacT/Alert automated culturing was used. For PCR, 1-ml aliquots were drawn from all (spiked) PCs on days 0, 1, 2, 3, 6 and 7 of storage. As a control, triplicate samples (10 ml) were inoculated into aerobic and anaerobic BacT/Alert culture bottles immediately after spiking (day 0) and after storage for 1, 2, 3, 6 or 7 days. With quantitative real-time PCR, all bacterial species tested were reproducibly detected on day 1 after spiking at original concentrations of 10 and 100 CFU/ml. Bacteria were also detected on day 1 from PCs spiked with an initial concentration of 1 CFU/ml, except for E. coli, which was detected in only one of the three samples and P. aeruginosa, for which analysis was not performed on day 1. With the reference method, bacteria were detected in culture bottles (inoculated on day 0) within a mean time of 20.1 h, with the exception of P. acnes which was detected at a mean time of 102.3 and 49.3 h (for original spiking concentrations of 10 and 100 CFU/ml respectively). PCR enables the rapid detection of low initial numbers of bacteria in PCs. For reliable detection, our results support that sampling of PCs for real-time PCR screening should not be carried out earlier than 1 day after preparation (48 h after blood collection). Importantly, the real-time PCR approach has the potential to be used before the release of PCs from the blood centre or shortly before they are transfused in the hospital.
    Vox Sanguinis 12/2005; 89(4):208-14. · 2.85 Impact Factor
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    ABSTRACT: Based on real-time polymerase chain reaction (PCR) technology, a broad-range 16S rDNA assay was validated and its performance was compared to that of an automated culture system to determine its usefulness for rapid routine screening of platelet concentrates (PCs). The presence of bacteria in pooled PCs was routinely assessed in an automated culturing system (BacT/ALERT, bioMerieux). The PCR assay was performed with DNA extracted from the same samples as used for culturing. DNA extraction was performed with a automated extraction system (MagNA Pure, Roche Diagnostics). PCR amplification was performed with a set of universal primers and probe targeting eubacterial 16S rDNA. A total of 2146 PCs were tested. Eighteen (0.83%) samples were found to be contaminated. These samples were positive for the presence of bacteria by both methods. All contaminants were identified as bacteria belonging to the common human skin flora. These included Propionibacterium spp. (n = 7), Staphylococcus spp. (n = 6), Bacillus spp. (n = 2), Micrococcus spp. (n = 2), and Peptostreptococcus spp. (n = 1). Estimation of the bacterial load in PCs by real-time PCR showed that the initial levels of contamination varied between 13.6 and 9 x 10(4) colony-forming unit equivalents per PCR procedure. Compared to culture in the BacT/ALERT system, the PCR assay had a sensitivity of 100 percent and a specificity of 100 percent. This real-time PCR assay has a much shorter turnaround time of 4 hours, which offers the possibility to test and obtain results on PCs before release or the day they are transfused. This would permit the withdrawal of contaminated PCs before transfusion.
    Transfusion 06/2005; 45(5):731-6. · 3.53 Impact Factor
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    ABSTRACT: Due to contamination of DNA extraction reagents, false-positive results can occur when applying broad-range real-time PCR based on bacterial 16S rDNA. Filtration of the nucleic acid extraction kit reagents with GenElute Maxiprep binding columns was effective in removing this reagent-derived contaminating DNA while the sensitivity of the assay was maintained.
    Journal of Microbiological Methods 06/2005; 61(2):285-8. · 2.16 Impact Factor
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    ABSTRACT: We applied real-time broad-range polymerase chain reaction (PCR) to detect bacteraemia in blood from febrile patients. Interpretation of amplification results in relation to clinical data and blood culture outcome was complex, although the reproducibility of the PCR results was good. Sequencing analysis of the PCR products revealed the presence of Burkholderia species DNA while no Burkholderia species grew in culture. The source of this contamination was shown to be the commercial DNA isolation kit used in the automated MagNA Pure Isolation Robot. A high degree of suspicion is required when uncommon or unexpected pathogens are diagnosed by molecular methods as clinical consequences can be serious.
    FEMS Immunology & Medical Microbiology 11/2004; 42(2):249-53. · 2.68 Impact Factor
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    ABSTRACT: BACKGROUND A real-time polymerase chain reaction (PCR) assay based on amplification of a conserved region of the HLA-DQA1 locus was developed and validated to assess its suitability in quantitating low levels of white blood cells (WBCs) in filtered platelet (PLT) concentrates (PCs). To determine the detection limit, serial dilutions of nonfiltered PCs with known quantities of WBCs were prepared. The analytical sensitivity and accuracy of the assay was tested with WBC concentrations ranging from 300 to 0.03 per microL with real-time PCR and flow cytometry. In addition, 126 random PCs were investigated to assess the capacity of the PCR method to quantify residual WBCs in clinical specimens. A sensitivity of 0.2 WBC equivalent per micro L (1.5 x 10(4) WBC equivalents/unit) was achieved. The assay was shown to be accurate and the HLA-DQA1 gene was reproducibly and consistently amplified in all tested samples (coefficient of variance of < 5%). Overall, the results of the PCR assay correlated well with those of the flow cytometry. The PCR assay detected a concentration of 3 WBCs per micro L (approximately 1 x 10(6) WBCs/unit) with 100 percent accuracy. Real-time PCR is rapid, sensitive, accurate, and reproducible. Hence this approach may prove suitable in routine monitoring of residual WBCs in PCs.
    Transfusion 09/2004; 44(9):1314-8. · 3.53 Impact Factor
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    ABSTRACT: A real-time PCR assay was developed for rapid detection of eubacterial 16S ribosomal DNA in platelet concentrates. The sensitivity of this assay can be hampered by contaminating DNA in the PCR reagents. Digestion of the PCR reagents with Sau3AI prior to PCR amplification was effective in eliminating this contaminating DNA without affecting the sensitivity of the assay.
    Journal of Clinical Microbiology 11/2003; 41(10):4796-8. · 4.07 Impact Factor

Publication Stats

194 Citations
30.85 Total Impact Points

Institutions

  • 2008
    • Sanquin Blood Supply Foundation
      Amsterdamo, North Holland, Netherlands
  • 2004–2006
    • VU University Medical Center
      • • Department of Medical Microbiology and Infection Control
      • • Department of Internal Medicine
      Amsterdamo, North Holland, Netherlands