Assessing the Impact of Collection, Production, and Storage of Platelet Concentrates on Bacterial Contamination and Product Safety

Abstract

The bacterial contamination of platelet concentrates (PCs) poses a safety risk to transfusion patients. Despite the implementation of mitigation strategies like donor skin disinfection and bacterial screening of PCs using culture methods, the anaerobic, slow growing bacterial contaminant Cutibacterium acnes is frequently transfused into patients. Fortunately, since this bacterium is incapable of proliferating in the aerobic PC storage environment, it has only been associated with mild adverse reactions. However, very little is known about the long-term impact of these transfusion events. This is particularly pertinent, since C. acnes is known to harbor a host of virulence factors that it can harness to cause slow developing, chronic infections, and the PC environment has been demonstrated to elicit the enhanced expression of virulence genes in other transfusion relevant bacteria. Furthermore, certain non-infectious transfusion reactions are driven by proinflammatory factors that accumulate in PCs during storage, and interestingly, bacterial interactions with platelets can elicit the release of these factors. It is therefore important to elucidate whether the transfusion of C. acnes contaminated PCs enhances the risk of such non-infectious adverse reactions. My thesis aims to elucidate the role that C. acnes contamination plays in the PC manufacturing process from blood collection to storage, and its impact on blood product safety. To that end, I hypothesized that C. acnes evades elimination during skin disinfection, contributing to its dominance as a bacterial contaminant of PCs. I further hypothesized that the virulence of C. acnes is heightened in the PC storage environment and C. acnes contamination results in an enhanced pro-inflammatory profile of PCs. The four objectives designed to test the hypotheses were to 1) investigate the ability of C. acnes to resist eradication by donor skin disinfectants, 2) enhance C. acnes detection through supplementation of culture media, 3) determine whether the PC storage environment enhances the virulence of C. acnes, and 4) evaluate whether PCs contaminated with C. acnes have an elevated pro-inflammatory profile. The data obtained in this study demonstrated that sebum components dampen the efficacy of the current blood donor skin disinfectant against C. acnes and may contribute to its dominance as a PC contaminant. I have also shown that the use of a commercially available supplement can reduce the detection time of C. acnes during PC screening with culture methods, the use of which has the potential to prevent the transfusion of C. acnes contaminated PCs. Furthermore, my data indicated that antigen shielding in PC derived C. acnes samples may reduce the acute immune response in a novel silkworm model, thereby dampening the virulence observed. However, the ability of C. acnes to adhere to mammalian epithelial cells and the expression of virulence genes involved in tissue invasion and persistence are enhanced in PCs, suggesting that the potential to cause chronic infections by C. acnes is augmented in this environment. Finally, I demonstrated that C. acnes contamination does not enhance the pro-inflammatory profile of PCs and therefore does not increase the risk of non-infectious adverse reactions. The research presented in this thesis has helped identify areas of improvement in the blood collection process and provided evidence for the use of supplements to enhance culture based bacterial screening for C. acnes. Notably, my work fills a void in our current understanding of the potential risks involved in transfusing C. acnes contaminated PCs. In conclusion, I have contributed to the advancement of knowledge in the field of transfusion medicine and provided insight into enhancing the safety of transfusion patients.