Detection of SCCmec elements amongst invasive Staphylococcus aureus isolates in Canterbury, New Zealand

  • Paul Huggan, Canterbury Health Laboratories, Christchurch, New Zealand
  • Mr Trevor Anderson, Canterbury Health Laboratories, Christchurch, New Zealand
  • Professor David Murdoch, Canterbury Health Laboratories and the University of Otago, Christchurch, New Zealand
  • Professor Steve Chambers, Christchurch Hospital and Univeristy of Otago, Christchurch

    • Objective: On a global level successful clones of Staphylococcus. aureus are commonly multi-drug resistant and have become widely disseminated. S.aureus isolates from blood in our region continue to show high levels of penicillin sensitivity (penicillin sensitive S.aureus, PSSA) and low levels (<1%) of MRSA. In a pilot study we sought to investigate the potential molecular mechanisms underpinning this observation.
    Method: 84 consecutive isolates for patients with S. aureus bacteraemia (PSSA=12, MSSA=70, MRSA=2) from 1/5/4 to 30/4/5 were examined. Extended antibiotic sensitivity testing was undertaken together with an in-house real-time PCR assay for detection of SCCmec right extremity (SRE) and chromosomal orfX gene sequences based on the method described by Huletsky et al.
    Results: SRE/orfX sequences were detected in 72/84 (84%) isolates studied (PSSA=9/12 (75%), MSSA=61/70 (87%), MRSA= 2/2 (100%)). No characteristic antibiogram was associated with SRE/orfX positivity.
    Conclusion: We provide compelling evidence for the integration of SCC-like elements into invasive strains of S.aureus in a region with high levels of penicillin and methicillin susceptibility.