Bacterial contamination is the major infectious hazard associated with transfusion of platelets (PLTs). Routine testing for bacterial contamination in platelet units has become common, but transfusiontransmitted bacterial sepsis has not been eliminate
d. Here, we describe a novel flow cytometry– based method for point-of-issue screening of PLTs for bacterial contamination.
We used the BactiFlow flow cytometer to detect and count bacteria based on esterase activity in viable cells. We compared the assay to incubation (BacT/Alert culture system) and rapid nucleic acid– based or immunoassay (reverse transcription PCR, Pan Genera Detection) methods.
We established a protocol for bacterial screening of PLTs consisting of enzymatic digestion and centrifugal filtration for the elimination of viable platelets and selective labeling of bacteria with fluorescent esterase substrate (ChemChrome V23). Results from the BactiFlow showed an excellent correlation (r = 0.9923 E. coli, r = 0.9736 S. epidermidis) to traditional plate count results. The lower detection limit of the assay was determined to be 150 CFU/mL, and the time to result was < 1 h.
Our study demonstrates that BactiFlow flow cytometry is suitable for rapid screening of PLTs for bacterial contamination and fulfils the requirements for a point-of-issue testing of PLTs with acceptable time to result, specificity, sensitivity, and cost.
© 2009 American Association for Clinical Chemistry
Institut fuer Laboratoriums- und Transfusionsmedizin, Herz- und Diabeteszentrum Nordrhein-Westfalen, Universitaetsklinik der Ruhr-Universitaet Bochum