title: Bacterial screening of platelet concentrates on day 2 and 3 with flow cytometry: the optimal sampling time point?
abstract: 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.
  
  
  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.
authors.affiliation: Institute of Laboratory and Transfusion Medicine, Heart and Diabetes Centre, Nordrhein-Westfalen, Ruhr University Hospital - Bochum University, Bad Oeynhausen, Germany.
authors.forename: Tanja
authors.initials: T
authors.lastname: Vollmer
authors.affiliation: DRK-West Blood Donation Service, Zentrallabor Hagen, Germany.
authors.forename: Volkmar
authors.initials: V
authors.lastname: Schottstedt
authors.affiliation: DRK-West Blood Donation Service, Zentrallabor Hagen, Germany.
authors.forename: Juergen
authors.initials: J
authors.lastname: Bux
authors.affiliation: DRK- West Blood Donation Service, Münster, Germany.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Walther-Wenke
authors.affiliation: Institute of Laboratory and Transfusion Medicine, Heart and Diabetes Centre, Nordrhein-Westfalen, Ruhr University Hospital - Bochum University, Bad Oeynhausen, Germany.
authors.forename: Cornelius
authors.initials: C
authors.lastname: Knabbe
authors.affiliation: Institute of Laboratory and Transfusion Medicine, Heart and Diabetes Centre, Nordrhein-Westfalen, Ruhr University Hospital - Bochum University, Bad Oeynhausen, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Dreier
mesh_terms: D001792:Blood Platelets / Q000382:microbiology*; D001793:Blood Preservation; D005260:Female; D005434:Flow Cytometry / Q000379:methods*; D006801:Humans; D008297:Male; D013203:Staphylococcal Infections; D013212:Staphylococcus epidermidis / Q000166:cytology*; D013997:Time Factors