Validation of a microbial detection system for use with ACD-A platelets with PAS III platelet additive solution

The BacT/ALERT microbial detection system (BTA) is used for testing leukoreduced apheresis platelets (LR-AP) in plasma. Platelet additive solutions (PASs) such as InterSol (PAS III) may be used to reduce the amount of plasma transfused in LR-AP. This study evaluated the performance of the two-bottle BTA testing scheme in the recovery of seeded microorganisms from LR-AP in InterSol-plasma compared to a reference plate culture method.

Hyperconcentrated, double LR-AP were collected from healthy donors; InterSol was added (65% Intersol:35% plasma), equally divided into two containers, and then inoculated with an isolate of 1 of 10 clinically relevant index organisms at two levels. Aerobic (BPA) and anaerobic (BPN) BTA bottles were inoculated with 4 mL each of the inoculated LR-AP, and blood agar plates (BAPs) for aerobic and anaerobic culture (0.5 mL each).

Zero false-positives from 103 bottle pairs were observed. All 400 two-bottle BTA tests were positive within 24 hours, except for Propionibacterium acnes (maximum time-to-detection of 86.4 hr) and 13 of 20 pairs of Streptococcus viridans (maximum time-to-detection of 31.7 hr). Thirteen of 400 BAP two-plate tests were negative for starting bacterial concentrations of 10 colony-forming units (CFUs)/mL or less. At 40 CFUs/mL or less, BTA was 100% positive while BAP was 94% positive.

Seeded organism recovery was superior in the two-bottle BTA test system compared to the two-plate BAP system using InterSol platelets (PLTs). This performance is comparable to previously published results for PLTs in plasma. The use of InterSol does not appear to have a detrimental effect on the performance of the two-bottle BTA system.