Global epidemiology and evolutionary history of Staphylococcus aureus ST45

Effelsberg N, Stegger M, Peitzmann L, Altinok O, Coombs GW, Pichon B, Kearns A, Randad PR, Heaney CD, Bletz S, Schaumburg F, Mellmann A

Abstract

Staphylococcus aureus ST45 is a major global MRSA lineage with a huge strain diversity and a high clinical impact. It is one of the most prevalent carrier lineages but also frequently causes severe invasive disease such as bacteremia. Little is known about its evolutionary history. In this study, we used whole genome sequencing to analyze a large collection of 451 diverse ST45 isolates from six continents and 26 countries. De novo assembled genomes were used to understand genomic plasticity and to perform coalescent analyses. The ST45 population contained two distinct sublineages, which correlated with the isolates' geographical origin. One sublineage primarily consisted of European/North American isolates, whilst the second sublineage primarily consisted of African and Australian isolates. Bayesian analysis predicted ST45 originated in North Western Europe about 500 years ago. Isolation time, host and clinical symptoms did not correlate with phylogenetic groups. Our phylogenetic analyses suggest multiple acquisitions of the SCCmec element and key virulence factors throughout the evolution of the ST45 lineage.