Colonisation with Staphylococcus aureus in remote Western Australian communities

  • Frances O'Brien, Gram-positive Bacteria Typing and Research Unit, Curtin University of Technology, Western Australia, Australia
  • A/Prof John Pearman, Gram-positive Bacteria Typing and Research Unit,PathWest Laboratory Medicine – WA, Royal Perth Hospital, Australia, Australia
  • Mr Geoffrey Coombs, Gram-positive Bacteria Typing and Research Unit, PathWest Laboratory Medicine – WA, Royal Perth Hospital, Australia, Australia
  • A/Prof Keryn Christiansen, Gram-positive Bacteria Typing and Research Unit,PathWest Laboratory Medicine – WA, Royal Perth Hospital, Australia, Australia
  • Prof Warren Grubb, Gram-positive Bacteria Typing and Research Unit, Curtin University of Technology, Western Australia, Australia

    • Background: Community associated methicillin-resistant S. aureus (CA-MRSA) was first observed in remote Western Australian (WA) communities in the early 1980s and has now become a problem throughout the general WA community.
    Methods: To understand more about CA-MRSA in WA 2,146 people living in 20 remote WA communities from three geographical regions have been screened at multiple sites for colonisation with S. aureus and the genetic backgrounds of the colonising strains have been established.
    Results: The prevalence for S. aureus was 37%, and 7.6% of the people harboured CA-MRSA. Combined colonisation with CA-MRSA and community acquired methicillin-susceptible S. aureus (CA-MSSA) was found on 3.4% of the people. Two percent and 12% of the population harboured CA-MRSA and CA-MSSA respectively at multiple sites. For each person colonised at multiple sites the CA-MRSA tended to belong to the same genetic lineage while the CA-MSSA mostly belonged to different lineages. There were differences in the local prevalence of S. aureus throughout the geographical regions. The prevalence of colonisation for the individual communities ranged from 17 to 83% for S. aureus, 16 to 61% for CA-MSSA and 0 to 37% for CA-MRSA. The importance of screening both anterior nares and the throat was demonstrated. Twenty-two clones of S. aureus belonging to 13 clonal complexes and 2 singleton lineages together with 56 sporadic isolates were found. Five lineages contained CA-MRSA, three of which are considered to be endemic in the communities. The three lineages of CA-MRSA that were considered to be endemic in the remote communities are the predominant lineages of CA-MRSA currently found in the general WA community.
    Conclusions: The epidemiology of CA-MRSA and CA-MSSA in remote WA communities has had important implications for the current epidemiology of CA-MRSA in the general WA community.