Genotyping as a tool for naming epidemic methicillin-resistant Staphylococcus aureus strains in Finland

Abstract number: p460

Vainio  A., Karden-Lilja  M., Ibrahem  S., Kerttula  A., Salmenlinna  S., Virolainen  A., Vuopio-Varkila  J.


We used several molecular genotyping methods of S. aureusto analyze clonal grouping of the EMRSA strains in Finland with a purpose of renewing their nomenclature. The other objective was to refine the genotyping scheme to better support local outbreak investigations.


Finnish epidemic MRSA strains from years 1991 to 2004 were tested with several molecular genotyping methods. Pulsed field gel electrophoresis (PFGE) was used as the primary method to distinguish different EMRSA strains. In addition, multi locus sequence typing (MLST) of seven housekeeping gene alleles, staphylococcal cassette chromosome mec (SCCmec) analysis of mobile methicillin-resistance genetic element (I-V), and spa-typing to identify the polymorphic X-region of protein A of S. aureus were used. The clonal complex analysis based on spa and MLST results was performed by BURP and eBURST programs, respectively.


PFGE identified 44 different EMRSA strains. These strains represented all SCCmec elements (I-V). Spa-typing found 27 different spa-types among the 44 EMRSA strains, six of them being new spa-types that were not found previously from the Ridom SpaServer. The spa-types divided into four different clonal complexes and into six singletons. With MLST, we were able to find 20 different allelic profiles and those divided into 15 different clonal complexes. When all typing results were combined, the EMRSA strains clustered into 26 more closely related groups (FIN-1 to FIN-26) based on PFGE, SCCmec, spa-typing and MLST results. MLST and spa-typing results supported and specified clonal groupings of the Finnish EMRSA strains.


PFGE can be used as the primary molecular method for naming of MRSA strains in Finland. SSCmec, MLST and spa-typing are needed to verify clonal complexes. Usage of several different molecular typing methods is necessary for accurate nomenclature of MRSA, also in outbreak situations.

Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Location: Oxford, UK
Presentation type:
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