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Updated: Dec 20, 2025
Multiplex PCR Assay for Typing of Staphylococcal Cassette Chromosome Mec Types I to V in Methicillin-resistant Staphylococcus aureus
Published on: September 5, 2013
Repeated introduction and spread of the MRSA clone t304/ST6 in northern Europe
M D Bartels1, P Worning1, L P Andersen2
1Department of Clinical Microbiology, MRSA Knowledge Centre, Hvidovre Hospital, Denmark.
Objectives:
During the last decades several methicillin-resistant Staphylococcus aureus (MRSA) clones with the capability of global spread have emerged in the community. Here, we have investigated a large collection of clinical isolates belonging to MRSA clone t304/ST6, which has emerged in many European countries over the last years, in order to retrace its phylogeny and its spread.
Methods:
We characterized 466 ST6 isolates from Denmark (n = 354), France (n = 10), Norway (n = 24), Sweden (n = 27) and the UK (n = 51). All had spa-type t304 (n = 454) or t304-related spa-types (n = 12) and whole genome sequencing (WGS) was carried out on Illumina Miseq or Hiseq with 100-300 bp reads. cgMLST was performed using Ridom SeqSphere.
Results:
A minimum spanning tree (MST) of all 466 isolates showed one large cluster including 182 isolates collected only from Denmark and related to a long-term neonatal outbreak in Copenhagen. This cluster contrasted with numerous small clusters, including the remaining Danish isolates and isolates from the other countries that interspersed throughout the tree. Most isolates were Panton-Valentine leukocidin (PVL) negative (95%) and harboured SCCmec IVa. One genome was closed using Oxford Nanopore technology and Illumina MiSeq. It contained a plasmid of 19.769 bp including the blaZ gene. A similar plasmid was found in 78% of all isolates.
Discussion:
t304/ST6 is a successful emerging clone and the fact that isolates from five countries are interspersed throughout the MST indicates a common origin. This clone is commonly described in the Middle East and its emergence in Europe coincides with influx of refugees from the Syrian Civil War.
Insights
The methicillin-resistant Staphylococcus aureus (MRSA) t304/ST6 clone has spread across Europe, originating from a common source. Its emergence in Europe may be linked to refugee influx from the Syrian Civil War.
Area of Science:
- Microbiology
- Genomics
- Epidemiology
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) clones have emerged globally.
- The t304/ST6 MRSA clone has become prevalent in many European countries.
- Understanding the phylogeny and spread of emerging MRSA clones is crucial for public health.
Purpose of the Study:
- To investigate the phylogeny and spread of the MRSA t304/ST6 clone in Europe.
- To characterize clinical isolates of the t304/ST6 clone from multiple European countries.
Main Methods:
- Whole genome sequencing (WGS) of 466 MRSA ST6 isolates from Denmark, France, Norway, Sweden, and the UK.
- Characterization of spa-types, including t304 and related types.
- Core genome multilocus sequence typing (cgMLST) using Ridom SeqSphere.
Main Results:
- A minimum spanning tree (MST) revealed a large cluster of Danish isolates linked to a neonatal outbreak, distinct from other isolates.
- Most isolates (95%) were Panton-Valentine leukocidin (PVL) negative and harbored SCCmec IVa.
- A 19.769 bp plasmid carrying the blaZ gene was identified in one closed genome and found in 78% of isolates.
Conclusions:
- The t304/ST6 clone is a successful emerging MRSA clone with a common origin, evidenced by interspersed isolates from multiple countries.
- The clone's emergence in Europe coincides with the influx of refugees from the Syrian Civil War.
- Further research is needed to fully understand the dynamics of MRSA clone dissemination.
