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Background: Whole blood (WB) is held at room temperature for not more than 24 hours before blood component manufacturing. The ability of several culture collection, skin-derived, and transfusion-related bacteria to survive in WB stored at 22 ± 2°C for 24 hours was investigated in this study., Study Design and Methods: Twenty-one bacteria of the species Staphylococcus epidermidis, Staphylococcus aureus, Staphylococcus capitis, Streptococcus agalactiae, Serratia liquefaciens, Serratia marcescens, Klebsiella pneumoniae, Escherichia coli, and Yersinia enterocolitica were inoculated into 7-mL aliquots of WB at a concentration of 500 colony-forming units (CFU)/mL. Spiked WB was stored aerobically at 22 ± 2°C, and bacterial viability and growth were monitored at 3, 8, and 24 hours during WB storage. Bacteria that showed decreased viability during WB incubation were further characterized for their sensitivity to plasma factors and neutrophil killing., Results: There were three different scenarios for bacterial behavior during the hold of WB at 22 ± 2°C. Five bacteria proliferated (p < 0.03), 11 remained viable or showed low proliferation, and a third group of five bacteria had decreased or lost viability (p < 0.01). Three of the latter five bacteria were plasma-sensitive while the other two were plasma-resistant but susceptible to neutrophil killing (p = 0.01)., Conclusions: The bactericidal activity of WB can be the result of plasma sensitivity or neutrophil killing. Bacteria with a starting inoculum of 500 CFU/mL, and able to resist WB immune factors, can proliferate to clinically significant levels posing a potential safety risk to transfusion patients. Results of this pilot study should be validated under standard WB collection and storage conditions., (© 2019 AABB.)

Background: A 30-minute rule was established to limit red blood cell (RBC) exposure to uncontrolled temperatures during storage and transportation. Also, RBC units issued for transfusion should not remain at room temperature (RT) for more than 4 hours (4-hour rule). This study was aimed at determining if single or multiple RT exposures affect RBC quality and/or promote bacterial growth., Study Design and Methods: Growth and RT exposure experiments were performed in RBCs inoculated with Serratia liquefaciens and Serratia marcescens. RBCs were exposed once to RT for 5 hours (S. liquefaciens) or five times to RT for 30 minutes (S. marcescens) with periodic sampling for bacterial counts. Noncontaminated units were exposed to RT once (5 hr) or five times (30 min each) and sampled to measure in vitro quality variables. RBC core temperature was monitored using mock units with temperature loggers. Growth and RT exposure experiments were repeated three and at least six times, respectively. Statistical analysis was done using mixed-model analysis., Results: RBC core temperature ranged from 7.3 to 11.6°C during 30-minute RT exposures and the time to reach 10°C varied from 22 to 55 minutes during 5-hour RT exposures. RBC quality was preserved after single or multiple RT exposures. Increased growth of S. liquefaciens was only observed after 2 hours of continuous RT exposure. S. marcescens concentration increased significantly in multiple-exposed units compared to the controls but did not reach clinically important levels., Conclusion: Single or multiple RT exposures did not affect RBC quality but slightly promoted bacterial growth in contaminated units. The clinical significance of these results remains unclear and needs further investigation., (© 2012 American Association of Blood Banks.)