Platelet concentrates safety: a focus on the challenging pathogen Staphylococcus aureus—a narrative review

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Background and Objective: Contamination of platelet concentrates (PCs) with Staphylococcus aureus (S. aureus) is a significant concern in transfusion medicine. This pathogen can escape detection during routine PC screening with culture methods and in rare occasions resist pathogen reduction treatment. The aim of this narrative review is to provide up-to-date information on the modulation of molecular mechanisms of S. aureus that impact the safety of PC transfusion patients. Methods: Retrospective and observational studies were searched in PubMed and Google Scholar from January 2014 to October 2024 with the terms: “platelet concentrates”, “bacterial contamination”, “Staphylococcus aureus”, “transcriptome analyses”, “virulence factors”, and “metabolic adaptation”. Furthermore, analysis of comparative transcriptome data of S. aureus grown in PCs vs. media was added to complement/support findings of the literature review. Key Content and Findings: The literature review and transcriptome data revealed interesting phenotypic and genotypic characteristics of S. aureus, including expression of virulence determinants and adoption of alternative metabolic pathways in the harsh PC storage niche, posing a threat for transfusion patients. Although PCs provide a unique and challenging environment for S. aureus with a combination of physiological stressors, host defenses, and limited nutrient availability, this bacterium has developed sophisticated strategies to interfere with platelet immunomodulatory factors, resist immune clearance, and adapt to difficult survival conditions. Transcriptome analysis showed that the PC storage environment triggers upregulation of S. aureus genes responsible for cell wall modification, capsule production, and biofilm formation, which protect the bacterium from platelet and plasma-derived antimicrobial peptides, and environmental stressors. Additionally, genes encoding for proteins involved in alternative metabolic pathways, like anaerobic fermentation and nutrient acquisition, are upregulated in PCs compared to media. Comparative RNA-seq analyses of S. aureus cultured in PCs vs. media indicate that this bacterium switches onto a quiescent state to survive challenging PC storage conditions by minimizing energy expenditure, altering metabolic pathways, and enhancing resistance to environmental stresses. Conclusions: S. aureus adaptation to the PC storage environment results in molecular modulation of key factors involved in persistence and pathogenicity, posing a challenge for detection and eradication in contaminated PC units, with a potential detrimental outcome for transfusion patients.

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