The Epidemiology of Staphylococcus aureus and Panton-Valentine Leucocidin (pvl) in Central Australia, 2006-2010

Background: The Central Australian Indigenous population has a high incidence of Staphylococcus aureus bacteremia (SAB) but little is known about the local molecular epidemiology. Methods: Prospective observational study of bacteremic and nasal colonizing S.aureus isolates between June 2006 to June 2010. All isolates underwent single nucleotide polymorphism (SNP) genotyping and testing for the presence of the Panton-Valentine Leucocidin (pvl) gene. Results: Invasive isolates (n=97) were predominantly ST93 (26.6%) and pvl positive (54.3%), which was associated with skin and soft tissue infections (OR 4.35, 95% CI 1.16, 16.31). Non-multiresistant MRSA accounted for 31.9% of bacteremic samples and showed a trend to being healthcare associated (OR 2.16, 95% CI 0.86, 5.40). Non-invasive isolates (n=54) were rarely ST93 (1.9%) or pvl positive (7.4%). Conclusions: In Central Australia, ST93 was the dominant S.aureus clone, and was frequently pvl positive and associated with an aggressive clinical phenotype. Whether non-nasal carriage is more important with invasive clones or whether colonization occurs only transiently remains to be elucidated.