Clonality of epidemic methicillin-resistant Staphylococcus aureus strains in Finland as defined by several molecular methods

  • A. Vainio
  • M. Kardén-Lilja
  • S. Ibrahem
  • A. M. Kerttula
  • S. Salmenlinna
  • A. Virolainen
  • J. Vuopio-Varkila


In Finland, the incidence of methicillin-resistant Staphylococcus aureus (MRSA) strains has increased ten fold within the last decade. In order to follow the changing epidemiology of MRSA, accurate typing of S. aureus strains is important. The purpose of this study was to reanalyse 44 previously recognised Finnish epidemic MRSA strains (EMRSA) by several molecular typing methods and to revise their nomenclature. The 44 EMRSA strains were grouped into 26 pulsed-field gel electrophoresis (PFGE) clusters, 20 multi locus sequence typing (MLST) sequence types (ST) belonging to 12 clonal complexes (CC) of which CC8 was the most prevalent, and 27 spa types belonging to four clonal complexes. The staphylococcal cassette chromosome mec (SCCmec) type IV was predominant, and 48% of the strains were nonmultiresistant to antibiotics. The discriminatory power of PFGE clusters, MLST, and spa typing was high. The overall concordance values of typing methods differed when assessed by two different methods. Adjusted Rand coefficient provided fairly low correlations for all comparisons. However, spa type was able to efficiently predict types and clonal complexes of most of the other methods with high probability (≥80%).



We thank Heidi Husu for her skilled technical assistance. This data was partly presented at the 16th European Congress of Clinical Microbiology and Infectious Diseases, April 2006, Nice, France, Poster no. 460. We declare that the experiments comply with the current laws of Finland.


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Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • A. Vainio
    • 1
  • M. Kardén-Lilja
    • 1
  • S. Ibrahem
    • 1
  • A. M. Kerttula
    • 1
  • S. Salmenlinna
    • 1
  • A. Virolainen
    • 1
  • J. Vuopio-Varkila
    • 1
  1. 1.Department of Bacterial and Inflammatory DiseasesNational Public Health Institute (KTL)HelsinkiFinland

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