Growth and Distribution of Bacteria in Contaminated Whole Blood and Derived Blood Components.

INTRODUCTION: Bacterial contamination of blood products presumably occurs mainly during blood collection, starting from low initial concentrations of 10-100 colony-forming units (CFUs) per bag. As little is known about bacterial growth behavior and distribution in stored whole blood (WB) and WB-derived blood products, this study aims to provide data on this subject.

METHODS: WB units were inoculated with transfusion-relevant bacterial species ( Acinetobacter baumannii, Bacillus cereus, Escherichia coli, Klebsiella pneumoniae, Listeria monocytogenes, Pseudomonas fluorescens, Serratia marcescens, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus dysgalactiae, Streptococcus pyogenes, Yersinia enterocolitica ; n = 12 for each species), stored for 22-24 h at room temperature, and then centrifuged for separation into plasma, red blood cells (RBCs), and buffy coats (BCs). The latter were pooled with 3 random donor BCs and one unit of PAS-E each to yield plasma-reduced platelet concentrates (PCs). Samples for bacterial colony counting were collected after WB storage and immediately after blood component production. Sterility testing in PCs ( n = 12 for each species) was performed by bacterial culture after 7 days of storage.

RESULTS: Bacterial growth in WB varied remarkably between donations and species. Streptococcus species produced the highest titers in WB, whereas Staphylococcus aureus , Staphylococcus epidermidis , Escherichia coli, and Pseudomonas fluorescens did not multiply. Centrifugation resulted in preferential accumulation of bacteria in BCs, with titers of up to 3.5 × 103 CFU/mL in BCs and up to ≤0.9 × 103 CFU/mL in BC-derived PCs. Overall, 72/144 PCs (50%) tested positive for bacteria after storage. Sterility test results were species-dependent, ranging from 12 of 12 PCs tested positive for Streptococcus pyogenes to 1 of 12 PCs positive for Escherichia coli . Bacterial contamination of RBC and plasma units was much less common and was associated with higher initial bacterial counts in the parent WB units.

CONCLUSIONS: Bacterial growth in WB is species-dependent and varies greatly between donations. Preferential accumulation of bacteria in BCs during manufacturing is a critical determinant of the contamination risk of BC-derived pooled PCs.