Transfusion medicine handbook

7. Adverse Effects of Transfusion

7.9 Bacterial Sepsis

Bacterial sepsis, whilst rare, is the leading microbial cause of transfusion mortality. Sources of bacteria in blood components may include contamination from skin organisms at the phlebotomy site due to ineffective skin disinfection, skin plugs introduced to units during phlebotomy, transient bacteremia in donors and, rarely, contamination during handling and processing of components.

Bacterial contamination is more likely in components stored at room temperature (20 - 24°C) such as platelets, than with red cells (stored at 2 - 6°C). Common organisms associated with contamination include Staphylococcus epidermidis, Staphylococcus aureus, Bacillus cereus, Group B streptococci, Escherichia coli, Pseudomonas species and other gram-negative organisms. Sepsis due to contaminated platelets is thought to be both under-recognised and under-reported. Platelet-associated sepsis is not normally catastrophic and can occur several hours or longer post-transfusion making it difficult to associate with transfusion and thereby diagnose. This is in contrast to the sepsis and toxaemia from bacterially contaminated red cells which is often rapid and catastrophic, with reported mortality rates of up to 60%.

Septic and toxic reactions may be life threatening. If bacterial contamination is suspected, the transfusion must be stopped immediately and institutional guidelines for investigating a reaction strictly followed. Usual investigation will include urgent patient and blood unit culture and Gram stain. Initial treatment involves managing the haemodynamic complications of sepsis and administration of intravenous antibiotics covering the usual pathogens associated with transfusion sepsis (i.e. Gram negative and Gram positive bacteria, including Staphylococcus).

A number of measures are used by NZBS to minimise the risk of bacterial contamination in blood components. These include:

• Pre-donation identification and deferral of potentially bacteraemic donors
• Enhanced disinfection of the skin at the phlebotomy site
• Diversion of the initial 10 - 40 mL blood collected into a separate container
• Bacterial monitoring of platelet components using an automated bacterial detection system

Visual inspection of the blood component for abnormal appearance (such as discolouration or haemolysis) should be carried out both prior to release from the Blood Bank and before administration. Blood components must not be transfused beyond their expiry date.