Do ethnic differences in ca-MRSA strains relate to country of origin?: A comparison of prevalence and multi-Locus sequence types of non multi-resistant strains of ca-MRSA in Samoa and Auckland

  • Stephen Ritchie, University of Auckland, New Zealand
  • Prof John Fraser, University of Auckland, New Zealand
  • Dr Arthur Morris, Diagnostic Medical Laboratory, New Zealand
  • Dr Sharmini Muttaiyah, LabPLUS, Auckland City Hospital, New Zealand
  • Dr Sally Roberts, LabPLUS, Auckland City Hospital, New Zealand
  • Mr James Slater, University of Auckland, New Zealand
  • Prof Paul Rainey, New Zealand Institute for Advanced Study, Massey University, New Zealand
  • A/Prof Mark Thomas, University of Auckland, New Zealand

    • Auckland (New Zealand) is home to the largest population of Polynesian people in the world. Colonisation and disease caused by the Western Samoan Phage Pattern (WSPP/Oceania) strain of ca-MRSA is more common in Maori and Pacific people than in other ethnic groups living in Auckland. It is possible that higher rates of invasive disease in Pacific people living in Auckland are the consequence of colonisation by unusually virulent strains.
    Objective:To investigate 1]the prevalence of ca-MRSA in Auckland and Samoa and 2]the genetic structure of non-multi resistant ca-MRSA populations in Samoa and Auckland.
    Method:Isolates of SA were collected from people with wound infections throughout Western Samoa. The isolates were analysed in Auckland by established methods. The sole community testing laboratory in Auckland provided data about the prevalence of SA and MRSA in wound swabs. MLST was performed on the non-multi resistant ca-MRSA strains from Samoa and on a similar number of MRSA strains from people in Auckland.
    Results:SA was isolated from 188/400 (47%) patients in Samoa with infected wounds, and MRSA was found in 34/188 (18%). In Auckland over the same time period 8% of SA isolated from wound swabs in the community were methicillin resistant.
    The MLST data from ca-MRSA isolates from Auckland and Samoa will be used to examine patterns of genetic diversity and to determine whether allelic diversity is correlated with factors such as ethinicity and geography.