Influence of blood prestorage conditions and white blood cell filtration on the bacterial load of blood deliberately inoculated with Gram‐positive and Gram‐negative pathogens

Abstract

Currently, the bacterial contamination of blood constitutes one of the major infectious risks of transfusion. The aim of this study was to evaluate the bactericidal effect of blood on various bacterial species and to determine the influence of prestorage conditions and white blood cell (WBC) filtration on the reduction of the bacterial load in isolated red blood cells (RBCs). The growth kinetics of eight different species of bacteria were studied at 20 degrees C in deliberately contaminated RBC units. Further experiments evaluated the effect of prestorage conditions and WBC filtration on the viability of two model bacteria (Klebsiella oxytoca and Staphylococcus epidermidis) in comparison to previous results obtained with Yersinia enterocolitica. For bacteria susceptible to the bactericidal effect of blood (mainly Gram-negative rods), a reduction of the bacterial load was obtained within 2 h of prestorage at 20 degrees C. When the prestorage period was prolonged beyond 3 h at 20 degrees C, rapid growth was observed with some Enterobacteriaceae. Whereas WBC filtration reduced dramatically the viability of Y. enterocolitica, it had only a minimal effect on the viability of S. epidermidis and K. oxytoca. However, the two latter species of bacteria did not survive prolonged storage at 4 degrees C. Experiments conducted under realistic conditions are needed to determine whether it would be worthwhile recommending the rapid storage of RBCs at 4 degrees C after WBC reduction of the blood product.