Although rare, transfusion-associated bacterial contamination (TABC) is nowadays the main risk associated with platelet concentrate (PC) transfusion. Consequences vary from spontaneously resolving symptoms to severe sepsis and death. In this report we have summarised a case of bacterial contamination and sepsis during PC transfusion in a patient with acute myeloid leukaemia. Fifteen minutes after the PC transfusion began, she developed chills and rapidly worsened to septic shock. The episode was managed appropriately. The patient's blood cultures and PC unit cultures grew Escherichia coli. The microbiological susceptibilities of isolates from the patient and platelet bag were identical. No other source of E coli was found. Donor and blood products issued from the same donation investigations were negative. The causality between sepsis and PC transfusion might be difficult to confirm. As no method is available in daily practice to eliminate TABC risk, physicians should always consider TABC by immediately stopping the transfusion and conducting appropriate investigations.