Detection of bacteria in WBC-reduced PLT concentrates using percent oxygen as a marker for bacteria growth

The risk of receiving a PLT concentrate (PC) contaminated with bacteria may be 1000-fold greater than that of pathogenic viral transmission, yet surveillance for this risk is not generally practiced. A novel bacteria detection system (BDS) that overcomes the limitations of current systems is described. The BDS monitors percent oxygen (%O2) in air above aliquots of PCs that have been filtered to remove the confounding effect of respiring PLTs and residual WBCs.

One-day-old WBC-reduced whole-blood-derived PCs (WBPCs) were inoculated with bacteria at 100 to 500 CFU per mL. After 30 minutes, 2- to 3-mL aliquots were processed through a PLT-reducing filter into a sample pouch containing sodium polyanethol sulfonate and entrained air. After incubation at 35 degrees C for at least 24 hours, the %O2 was measured within the pouch. Noninoculated WBC-reduced WBPCs (n = 155), confirmed free of bacteria by routine culture, were tested in a like manner. Results from the latter group of WBC-reduced WBPCs were used to distinguish contaminated from noncontaminated units.

After a 24-hour incubation at 35 degrees C, 195 (96.5%) of the 202 sample pouches obtained from inoculated units were detected by the BDS. After an additional 6 hours at room temperature, those that remained and were tested were found positive. None of the noninoculated controls produced a positive reading.

The BDS is easy to use and provides good levels of sensitivity and specificity.