Molecular typing of methicillin resistant Staphylococcus aureus by real-time PCR based technologies

  • Dr Melanie Syrmis, Queensland Paediatric Infectious Diseases Laboratory, SASVRC, Royal Children's Hospital, Brisbane QLD, Australia
  • Jacqueline Schooneveldt, Microbiology, Pathology Queensland, Central Laboratory, Brisbane QLD, Australia
  • Dr David Whiley, Queensland Paediatric Infectious Diseases Laboratory, SASVRC, Royal Children's Hospital, Brisbane QLD, Australia
  • Dr Flavia Huygens, School of Life Sciences, Queensland University of Technology, Brisbane, Qld, Australia
  • A/Prof Theo Sloots, Queensland Paediatric Infectious Diseases Laboratory, SASVRC, Royal Children's Hospital, Brisbane QLD, Australia
  • Prof Graeme Nimmo, Microbiology, Pathology Queensland, Central Laboratory, Brisbane QLD, Australia

    • Objective: Methicillin-Resistant Staphylococcus aureus (MRSA) remains a significant pathogen worldwide. Molecular typing of MRSA provides valuable information for infection control, but traditional molecular typing methods including pulsed-field electrophoresis are time consuming and expensive. The advent of real-time PCR technology now allows for faster, less expensive methods for typing MRSA. In this study, two recently published real-time PCR based-typing systems were applied to MRSA isolates from Brisbane, Australia.
    Methods: 119 MRSA isolates collected from January 2006 to July 2007 were tested using a high resolution melting (HRM) analysis assay targeting the staphylococcal protein A (spa) locus as well as a SNP-Binary system targeting seven single nucleotide polymorphisms (SNPs; arcC210, tpi241/3, arcC162, gmk318, pta294, tpi36, pta383) in combination with five binary markers (pvl, cna ,sdrE, , pUB110, and pT181) and an additional SNP-based confirmatory test for ST-93 (Queensland clone).
    Results: The SNP-Binary analysis revealed 12 sequence types (ST) and/or clonal complex (CC) profiles with ST-93 the most prevalent (38 isolates) followed by CC30 (34 isolates) and CC1 (21 isolates). HRM analysis indicated 18 profiles, providing further discrimination of certain STs and CCs, including ST-93.
    Conclusion: The SNP-Binary typing method can discriminate the major clones existing in southeast Queensland, including ST-93. The Spa HRM assay can easily be performed to complement the SNP-Binary typing method and may provide a means of further characterising MRSA.