pseudomonas poaeassociated fatal septic transfusion reaction peoria illinois usa 2017 in the united states fatal transfusiontransmitted infections from red blood cell units are rare although this pattern mostly reflects how inhospitable refrigerated red blood cell units are to contaminant growth fatalities caused by microorganisms that can grow at storage temperature 4c but not in standard clinical blood cultures at 37c are probably underestimated we analyzed a fatal red blood cell transfusion in peoria illinois usa that occurred in 2017 samples from the patients whole blood and the red blood cell unit remained culturenegative during the investigation despite direct visualization of gramnegative bacilli within the unit immediately after transfusion we identified the bacteria as pseudomonas poae a nonpathogenic pseudomonad carrying multiple coldshock domain protein genes and confirmed its cold tolerance and inability to grow at 37c our work indicates transfusion reaction workups need to include testing for psychrophilic organisms which could explain the cause of other apparently culturenegative transfusion reactions