Comparison of an ST80 MRSA strain from the USA with European ST80 strains

Objectives: A number of community-acquired MRSA (CA-MRSA) clonal lineages dominate worldwide. ST80 was dominant in Europe and has increasingly been described from the Middle East. Herewe report the whole genome sequence of the first ST80 CA-MRSA from the USA. Methods: CA-MRSA isolate S0924 was obtained from a patient admitted to Cook County Hospital (Chicago, IL, USA) who came from Syria; the isolate belonged to spa type t044 and ST80. The whole genome sequence of S0924 was determined and compared with three previously published whole genome sequences of ST80 CA-MRSA from Europe and a newly sequenced ST80 CA-MRSA from the Netherlands (S1475). Results: Based on spa typing, SCCmec type and virulence gene profile, this US ST80 isolate is indistinguishable from the European CA-MRSA ST80 clone. SNP analysis within the conserved core genome showed clear differences between the strains with up to 144 SNPs differing between S0924 and strain S1800, an ST80 MRSA from Greece. The gene content showed 21 regions of difference between the US and European isolates, although these were largely restricted to mobile genetic elements. Phylogenetic reconstruction indicated that the European strains were more closely related to each other than to the US strain. The SNP data suggest that a common ancestor existed around two decades ago, indicating that the US and European ST80 strains are clonally linked. Conclusions: These data combined with the country of origin of the patient suggest that ST80 S0924 was probably relatively recently introduced into the USA from Syria.