Staphylococcus aureus ST59: Concurrent but Separate Evolution of North American and East Asian Lineages.

Jo-Ann Mcclure,Osahon Obasuyi,Amani Niazy,Paul Gordon,John M Conly,Sidong Chen,Kunyan Zhang,Sahreena Lakhundi,George Dong

doi:10.3389/fmicb.2021.631845

Abstract

Despite initially being described in North America, Staphylococcus aureus (SA) sequence type ST59 is the most commonly isolated sequence type in Eastern Asia. The origins and evolution of this strain type remains unclear and therefore we gathered a collection of ST59 isolates from Canada and mainland China for a detailed genetic analysis of the lineage. Bayesian inference phylogenomic analysis of our isolates, along with previously published ST59 sequences indicated that the lineage could be divided into 6 distinct subgroups (WGS-1 thorough 6), each having distinct molecular characteristics. Analysis also demonstrated the concurrent but separate evolution of North American and East Asian lineages, as well as the extensive diversification of the East Asian lineage. The presence of a mobile element structure (MES) was found to be the major difference between these two continental lineages, absent in all North American isolates, and present in all East Asian ones. Other mobile genetic elements, such as the Immune Evasion Complex (IEC), Panton Valentine Leukocidin (PVL), and Staphylococcal Cassette Chromosome mec (SCCmec), showed significant variability within each sub-group and likely represents local selective pressures rather than major characteristics defining the groups. Our analysis also demonstrated the existence of a more ancient ST59 sub-lineage from North America, which was MES negative and contained some of the earliest reported ST59 isolates. Combined with the existence of a MES negative isolate from Taiwan, predicted to have appeared prior to diversification of the East Asian lineages, these results hint at the possibility of a North American origin for the lineage, which gained hold in Eastern Asia following acquisition of MES, and subsequently diversified.

Highlights

Methicillin-resistant Staphylococcus aureus (MRSA) is an important human pathogen that causes a wide variety of infections ranging from skin and soft tissue infections to endocarditis and sepsis (Diekema et al, 2001)
Pulsed field gel electrophoresis represents the traditional method for typing S. aureus, and for identifying different strain types
Within our complete collection of S. aureus strains, we identified 224 ST59 isolates, from which we generated a ST59 group specific pulsed field gel electrophoresis (PFGE) figure (Supplementary Figure 1)

Summary

Introduction

Methicillin-resistant Staphylococcus aureus (MRSA) is an important human pathogen that causes a wide variety of infections ranging from skin and soft tissue infections to endocarditis and sepsis (Diekema et al, 2001). Genetic analysis using multilocus sequence typing (MLST) has revealed that community-associated MRSA (CA-MRSA) can be divided into five major lineages, including sequence types ST1, ST8, ST30, ST59, and ST80, they differ in their geographic dominance (Mediavilla et al, 2012; Chen and Huang, 2014). While MRSA sequence type ST8 (PFGE type USA300) has been the predominant CA-MRSA isolated in North America and some parts of Europe (Monecke et al, 2011), ST59 represents the most prevalent sequence type isolated in Eastern Asia, representing the major cause of skin and soft tissue infections, as well as being described as a commensal colonizer (Takano et al, 2007; Chen et al, 2013). While ST59 is reported in other parts of the world, such as Europe and North America, it is not as commonly encountered in those regions

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