(P-TS-1) A Curious Case of Bacteremia

Background/Case Studies: Septic transfusion reactions (STR) are rare in red blood cell (RBC) transfusions. Gram-positive (GP) bacteria found on skin are the most frequent blood component contaminants, but are not typically associated with RBCs as they are stored at 1-6°C. Rather, RBCs implicated in STRs are more likely to be associated with gram negative bacteria. We report a STR that initially appeared to be due to GP bacterial contamination of an RBC unit.

Study

Design/Methods: Case report. Remnant RBC and plasma samples were sent to the clinical microbiology laboratory for aerobic bacterial culture in the same manner as clinical specimens. Whole genome sequencing (WGS) of pure bacterial isolate was performed on the MiSeq Sequencing System (Illumina, San Diego, CA)

Results/Findings: A patient with history of gastric adenocarcinoma was transfused 1 unit of RBCs for a hgb of 5.6 g/dL. Temperature prior to transfusion was 37.3°C and 39.7°C after. Heart rate was 94 beats per minute (bpm) pre-transfusion and 118 bpm post with no other symptoms. Laboratory investigation ruled out hemolysis. Gram stains of the patient’s blood and the sample collected from the port of the RBC unit were positive for GP cocci in clusters; both cultures identified Staphylococcus epidermidis. Culture of the plasma concurrent with the RBC unit was negative, resulting in further inquiry. WGS of the bacteria isolated from the RBC unit and the patient’s blood culture confirmed they were genetically identical. Patient pre-transfusion blood culture was unavailable. Clinical history revealed the patient had a chest port and recent peritoneal fluid infection with coagulase negative Staphylococcus; yet, this specimen had been discarded. Review of pre-transfusion peripheral blood smear unusually demonstrated numerous visible bacteria; Review of a pre-transfusion gram stain confirmed the presence of GP cocci in clusters, consistent with S. epidermidis. Further discussion with the nurse transfusionist revealed the transfusion proceeded per protocol except when the transfusion was discontinued, the lines attached to the unit were not flushed prior to return to the blood bank. Repeat culture of the RBC unit was then done from a different location (superior-lateral side of the bag) and was negative. Overall, the evidence suggested the patient had bacteremia prior to transfusion; the source of the patient’s bacteremia was attributed to the chest port which was potentially seeded by recent peritoneal infection. The RBC port may have been contaminated when the unit was sent via the pneumatic tube with unflushed tubing attached; we concede that there is no definitive explanation.

Conclusions: We present an interesting case that initially met diagnostic criteria for STR. Follow-up investigation, instigated by the unusual nature of GP bacteria in an RBC unit and negative culture in the concurrent plasma, revealed the patient most likely had GP bacteremia pre-transfusion.