Comparative genome analyses of Staphylococcus aureus from platelet concentrates reveal rearrangements involving loss of type VII secretion genes.

has been involved in transfusion-transmitted fatalities associated with platelet concentrates (PCs) due to its heightened pathogenicity enhanced by genome-encoded virulence and antibiotic resistance genes. This may be facilitated by mobile genetic elements (MGEs) that can cause rearrangements. Several factors contribute to virulence, including the type VII secretion system (T7SS), composed of six core genes conserved across strains. In this study, we conducted comparative genome analyses of five isolates from PCs (CI/BAC/25/13 /W, PS/BAC/169/17 /W and PS/BAC/317/16 /W were detected during PCs screening with the BACT/ALERT automated culture system, and ATR-20003 and CBS2016-05 were missed during screening and caused septic transfusion reactions). Multiple alignments of the genomes revealed evidence of rearrangements involving phage Sa3int in PS/BAC/169/17 /W and PS/BAC/317/16 /W. While the former had undergone translocation of its immune evasion cluster (IEC), the latter had lost part of the phage, leaving behind the IEC. This observation highlights genome plasticity. Unexpectedly, strain CBS2016-05 was found to encode a pseudo-type VII secretion system (T7SS) that had lost five of the conserved core genes (, and ) and contained a 5' truncated . Since these genes are essential for the function of the T7SS protein transport machinery, which plays a key role in virulence, CBS2016-05 probably compensates by recruiting other export mechanisms and/or alternative virulence factors, such as neu-tralizing immunity proteins. This study unravels genome rearrangements in isolated from PCs and reports the first isolate lacking conserved T7SS core genes.