Bacterial contamination screening

We sample each platelet component at least 36 hours after collection. 

Samples are then screened on the bioMérieux BACT/ALERT Automated Microbial Detection System, which uses both aerobic and anaerobic culture bottles. 

After sampling, platelets are released to inventory as “culture negative to date” but the culture bottles will continue to be incubated for a total of 7 days post inoculation. 

What if there’s a positive result?

If a culture becomes positive, the screening equipment automatically flags this as ‘initial machine positive’ (IMP).

An IMP could be either a false positive flag or indicate bacterial growth.

As a sample could potentially flag as a positive at any time, we’ve set up remote monitoring of the testing system 24 hours a day, 7 days a week (24/7). We also have 24/7 recall with a National Recall Office.

If the platelets and/or their associated components (e.g. red cell or clinical plasma) have already been issued at the time of the IMP, our National Recall Office notifies the relevant transfusion laboratory to return the implicated platelet and any associated components to Lifeblood.

If the component has been transfused, the transfusion laboratory will contact the treating clinician so they can manage the patient with the knowledge of the preliminary result.

We send all positive culture bottles to an external reference laboratory to have a Gram stain and culture.  

Gram stain results are generally available several hours after the IMP is obtained and then notified to the transfusion laboratory.

If microbial culture is successful, organism identification is performed. Antibiotic sensitivity is also reported if the component has been transfused. As relevant additional information becomes available, a progress report is sent to the transfusion laboratory, such as donor information that might assist in the management of the transfused patient or further information, including bacterial identification and antibiotic sensitivity.

In all cases where components have been transfused, a final report is forwarded to the transfusion laboratory when all laboratory investigations are complete. 

Updated September 2025