Genetic diversity of methicillin-resistant Staphylococcus aureus in a Dutch university hospital between 2002 and 2006

  • Eric Nulens, General Hospital St. Jan, Brugge, Belgium
  • Dr Ellen Stobberingh, University Hospital Maastricht, The Netherlands
  • Helke van Dessel, University Hospital Maastricht, The Netherlands
  • Maaike Welling, University Hospital Maastricht
  • Silvie Sebastian, University Hospital Maastricht, The Netherlands
  • Dr Frank van Tiel, University Hospital Maastricht, The Netherlands
  • Dr Patrick Beisser, University Hospital Maastricht, The Netherlands
  • Ruud Deurenberg, University Hospital Maastricht, The Netherlands

    • Objective
    The increased MRSA prevalence in The Netherlands during recent years may be due to increased cross-border healthcare and its associated spread of MRSA, or due to an increased CA-MRSA prevalence. The objective of this study was to test this hypothesis by characterizing MRSA strains isolated in our hospital during recent years.

    Methods
    MRSA isolates (n=175), isolated between January 2002 and December 2006 (n=32, 29, 35, 39, and 40 respectively), were characterized by spa and SCCmec typing. PVL was determined by real-time PCR.

    Results
    Between 2002 and 2005, ST5-MRSA-IV was the most prevalent clone in the azM. However, the spa type changed from t002 to t447 during these years. Besides ST5-MRSA-IV, ST5-MRSA-I, ST5-MRSA-II, ST228-MRSA-I, and ST247-MRSA-I were observed sporadically. From 2005, the genetic background of the MRSA clones became more diverse and during 2006, ST5-MRSA-IV was only sporadically observed. From 2005, ST5-MRSA-II, ST8-MRSA-IV (PVL-negative), ST22-MRSA-IV and ST45-MRSA-IV were increasingly observed. Four PVL-positive MRSA strains, isolated in 2005 and 2006, belonging to ST8-MRSA-IV (n=1) and ST80-MRSA-IV (n=3), were observed.

    Conclusions
    ST5-MRSA-I, ST5-MRSA-II, ST5-MRSA-IV, ST22-MRSA-IV and ST228-MRSA-I have not been described before in The Netherlands. However, these MRSA clones have previously been found in Belgium or Germany. The increased MRSA prevalence in The Netherlands is probably due to the introduction of new MRSA clones into The Netherlands, possible through cross-border healthcare. The prevalence of PVL-positive MRSA is low in our hospital.