Limited adaptive evolution of Staphylococcus aureus during transition from colonization to invasive infection

Staphylococcus aureus carriage is a risk factor for invasive infections. Unique genetic elements favoring the transition from colonizing to invasive phenotype have not been identified so far and phenotypic traits are understudied. We therefore assessed pheno- and genotypic profiles of eleven S. aureus-colonized patients suffering from invasive S. aureus infections aiming to identify patterns common to colonizing or invasive behavior. Systematic analysis of colonizing and invasive isolate pairs showed similar adherence, hemolysis and reproductive fitness properties and minimal genetic differences. Antibiotic tolerance and bacterial virulence in Galleria mellonella were identical between the colonizing and invasive strains. Our results provide insights into the similar phenotype associated with limited adaptive genetic evolution between the colonizing and invasive isolates. Disruption of the physical barriers mucosa or skin were identified in the majority of patients further emphasizing colonization as a major risk factor for invasive disease.