Abstract
BACKGROUND: Cutibacterium acnes contaminated platelet concentrates (PCs) are transfused due to late detection during culture-based screening. C. acnes has been implicated in mild adverse transfusion reactions; however, it harbors multiple virulence genes and can cause chronic infections in the clinical setting. Since the PC storage environment enhances virulence gene expression in bacteria like Staphylococcus aureus, this study aimed to evaluate the impact of PC storage on C. acnes virulence and its potential to cause chronic infections. STUDY DESIGN AND METHODS: PCs and media were inoculated with C. acnes (BPNBT-19195 and BPNBT-19329) and S. aureus (CBS 2016-05, control) PC isolates. Following incubation for 5 days (20-24°C/agitation), bacterial virulence was compared in the Bombyx mori (silkworm) model. Additionally, silkworm innate response (hemolymph melanization and superoxide dismutase activity (SOD)), adhesion to HEK293T epithelial cells, and differential expression of virulence genes involved in tissue invasion (hyl, mce) and persistence (roxP, lipase) were assessed in C. acnes samples. RESULTS: PC-derived C. acnes caused significantly lower larval mortality, hemolymph melanization, and SOD activity compared to media-derived counterparts; conversely, PC-derived S. aureus caused significantly higher larval mortality. Furthermore, PC-derived C. acnes displayed higher adherence to HEK293T cells and heightened virulence gene expression compared to media controls. DISCUSSION: Our data demonstrated that the PC milieu enhances the ability of C. acnes to adhere to mammalian epithelia and promotes the expression of genes involved in invasion and persistence in host tissue, potentially priming this bacterium to cause chronic infections in transfusion patients, which warrants further investigation.