Bacterial contamination of platelet components not detected by BacT/ALERT^®

To investigate the possible causes for false negative results in BacT/ALERT^® 3D Signature System despite bacterial contamination of platelet units.

The Northern Ireland Blood Transfusion Service (NIBTS) routinely extends platelet component shelf life to 7 days. Components are sampled and screened for bacterial contamination using an automated microbial detection system, the BacT/ALERT^® 3D Signature System. We report on three platelet components with confirmed bacterial contamination, which represent false negative BacT/ALERT^® results and near-miss serious adverse events.

NIBTS protocols for risk reduction of bacterial contamination of platelet components are described. The methodology for bacterial detection using BacT/ALERT^® is outlined. Laboratory tests, relevant patient details and relevant follow-up information are analysed.

In all three cases, Staphylococcus aureus was isolated from the platelet residue and confirmed on terminal sub-culture using BacT/ALERT^® . In two cases, S. aureus with similar genetic makeup was isolated from the donors.

Risk reduction measures for bacterial contamination of platelet components are not always effective. Automated bacterial culture detection does not eliminate the risk of bacterial contamination. Visual inspection of platelet components prior to release, issue and administration remains an important last line of defence.