Chimeric Staphylococcus aureus strains from waterfowl

When characterising S. aureus isolates from waterfowl, isolates were identified as atypical CC133 by DNA microarray analysis. They differed from previously sequenced CC133 strains in the presence of the collagen adhesin gene cna; some also showed a different capsule type and a deviant spa type. Thus, they were subjected to whole genome sequencing. This revealed multiple insertions of large regions of DNA from other S. aureus lineages (CC522 and CC692) into a CC133-derived backbone genome. These findings highlight the role of horizontal gene transfer in the evolution of S. aureus facilitated by SCC elements, by phages, and by a yet undescribed mechanism for large scale exchange of core genomic DNA.