Building evidence for transfusion practice: A pilot study on bacterial adhesion and growth in red blood cell infusion sets

BACKGROUND: Blood administration sets are changed after a prescribed time interval with variations in guidelines. In Canada, sets are changed every 4 h based on the theory of potential bacterial attachment. This study aimed to investigate whether bacteria adhere to the inner surfaces of blood administration sets during mimicked transfusions of red blood cell concentrates (RBCCs). STUDY DESIGN AND METHODS: Serratia marcescens was used to test bacterial adhesion on a Primary PLUM Y-type Blood Set. Study phases (N ≥ 3): (i) RBCCs spiked with 10 CFU/mL and bacterial recovery after 4 h; (ii) and (iii) RBCCs spiked with 1 CFU/mL and bacterial recovery after 2 h (ii) and after 2 h and 24 h (iii); (iv) RBCCs inoculated with 0.1 CFU/mL and bacterial detection at 2-24 h. Bacterial adhesion was verified with dislodging, cultures, and scanning electron microscopy after completion of mimicked RBCC transfusions. RESULTS: At 10 CFU/mL, S. marcescens was recovered in one of three assays; however, at 1 CFU/mL, bacterial recovery after 2 h was minimal (one of six assays), although proliferation at 24 h was significant. With initial loads of 0.1 CFU/mL, bacteria were only detected at 8 and 24 h, and in the filter, in one of five trials. CONCLUSION: This pilot report provides evidence of bacterial growth in transfusion sets. Data obtained with S. marcescens indicate that the use of blood administration sets could be extended from 4 to ≥6 h after the infusion of the first RBCC with no impact on patient safety. These findings align with existing guidelines endorsing a longer interval between changes of blood product administration sets.