From contamination to fever: The role of endotoxin levels in bacterially contaminated platelet concentrates

Background and Objectives Growth of gram‐negative bacteria in a platelet concentrate (PC) is inevitably accompanied by the accumulation of endotoxin, which is the major component of the outer cell membrane of these organisms. However, less is known about the kinetics of endotoxin accumulation in PC and its biological activity. Therefore, the endotoxin level of Klebsiella pneumoniae contaminated PCs was measured over time. In addition, the biological activity of the contaminants was analysed by an assay that mimics the human fever response in vitro. Materials and Methods The bacterial endotoxin test and the monocyte activation test were established for PC samples for endotoxin and pyrogen detection, respectively. Low‐count spiking of PCs using K. pneumoniae PEI‐B‐P‐08 was performed by six laboratories, and samples were taken over time. The samples were analysed for the number of viable cells, the amount of endotoxin and their capacity to induce the production of fever‐inducing cytokine interleukin 6 (IL‐6). Results K. pneumoniae showed fast proliferation in contaminated PCs reaching stationary phase 36 h post‐spiking. Endotoxin was measurable in samples with a bacterial load of more than 10 3 CFU/mL and increased proportionally to the number of bacteria present. IL‐6 production was found to be linked to endotoxin levels in PCs reaching levels of high pyrogenicity 24 h post‐spiking. Conclusion PCs contaminated with more than 10 3 CFU/mL of K. pneumoniae might be a risk for patients due to their ability to induce pyrogenic reactions during transfusion.