Bacterial growth kinetics in ACD‐A apheresis platelets: comparison of plasma and PAS III storage

BACKGROUND: Our objective was to determine the growth kinetics of bacteria in leukoreduced apheresis platelets (LR‐AP) in a platelet (PLT) additive solution (PAS; InterSol, Fenwal, Inc.) compared to LR‐AP stored in plasma. STUDY DESIGN AND METHODS: Hyperconcentrated, double‐dose LR‐AP were collected from healthy donors with a separator (AMICUS, Fenwal, Inc.). LR‐AP were evenly divided, InterSol was added to half (65% InterSol:35% plasma [PAS]), and PLTs in autologous plasma were used for a paired control (PL). Bacteria were inoculated into each LR‐AP PAS/PL pair (0.5‐1.6 colony‐forming units [CFUs]/mL), and bacterial growth was followed for up to 7 days. Time to the end of the lag phase, doubling times, maximum concentration (conc‐max), and time to maximum concentration (time‐max) were estimated. RESULTS: Streptococcus viridans did not grow to detectable levels in either PAS or PL units. The other bacteria had no significant overall difference in the conc‐max (p = 0.47) or time‐max (p = 0.7) between PL and PAS LR‐AP; PL had a 0.14 hours faster doubling rate (p = 0.023); and PAS had a 4.7 hours shorter lag time (p = 0.016). CONCLUSION: We observed that five index organisms will grow in LR‐AP stored in a 35%:65% ratio of plasma to InterSol where initial bacterial concentrations are 0.5 to 1.6 CFUs/mL. The more rapid initiation of log‐phase growth for bacteria within a PAS storage environment resulted in a bacterial concentration up to 4 logs higher in the PAS units compared to the plasma units at 24 hours, but with no difference in the conc‐max. This may present an early bacterial detection advantage for PAS‐stored PLTs.