Transfusion of a platelet pool contaminated with exotoxin-producing Staphylococcus aureus: a case report

Staphylococcus aureus (S. aureus) contamination of platelet concentrates (PCs) has become a leading cause of transfusion-transmitted infections in recent years. S. aureus has been known to escape detection during routine PC screening with culture methods leading to septic transfusion reactions. This report describes a bacterial-associated transfusion event in an elderly patient diagnosed with acute promyelocytic leukemia, who was transfused with a 5-day old buffy coat platelet pool. The transfusion was interrupted due to changes in the cardiorespiratory status of the patient, followed by septic shock symptoms including severe chest pain, shortness of breath, chills/rigors, nausea/vomiting, transient hypoxemia, and fever. The patient was successfully treated with analgesics and nitroglycerine spray. Cultures performed on the patient`s blood and the residual PC unit were positive for S. aureus. PCR and Western blot analyses showed that the S. aureus isolate produces the superantigen enterotoxin type G, which was detected in residual PC obtained after the transfusion event. In conclusion, microbiological analyses of patient’s blood samples and transfused PC reveal bacterial infection with severe post-transfusion symptoms due to S. aureus contamination. This is classified as a false-negative transfusion septic case as the implicated PC was negative for bacterial contamination during routine screening with automated culture. This report substantiates the increasing cases of S. aureus as a major PC contaminant with severe clinical consequences, and exposes the potential dangers associated with exotoxin-producing isolates.