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Overlapping population structures of nasal isolates of Staphylococcus aureus from healthy Dutch and American individuals.

Melles DC, Tenover FC, Kuehnert MJ, Witsenboer H, Peeters JK, Verbrugh HA, van Belkum A

Erasmus MC, University Medical Center Rotterdam, Department of Medical Microbiology & Infectious Diseases, s-Gravendijkwal 230, 3015 CE Rotterdam, The Netherlands; Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, 1600 Clifton Road NE (G-08), Atlanta, GA 30333, USA; Department of Microbial Genomics, Keygene N.V., Agro Business Park 90, 6708 PW Wageningen, The Netherlands; Erasmus MC, University Medical Center Rotterdam, Department of Bioinformatics, Dr. Molewaterplein 50, 3015 GE Rotterdam, The Netherlands.

To understand Staphylococcus aureus nasal carriage and its relation with subsequent disease, insight into the natural (non-clinical) bacterial population structure is essential. This study aimed to investigate whether the distribution of S. aureus genotypes that cause colonization differs by geographic locales. High-throughput amplified fragment length polymorphism (AFLP) analysis was performed on nasal isolates of S. aureus from healthy American (n = 391) and Dutch (n = 829) volunteers. In total, 164,970 binary outcomes, covering 135 different markers per isolate, were scored. Methicillin-resistance was defined for all strains; pulsed-field gel electrophoresis (PFGE) typing was performed for the American isolates. The overall population structures of the American and Dutch S. aureus isolates were comparable. The same four major AFLP clusters (I - IV) and subclusters were identified in both collections. However, the Dutch methicillin-susceptible S. aureus (MSSA) isolates were overrepresented in AFLP cluster III (P = 0.0016). Furthermore, the majority of the American MRSA isolates (90.5%) were located in AFLP cluster I (P < 0.0001). This identifies differences in the local prevalence of certain S. aureus genotypes. AFLP clusters II and III, which represent MLST clonal complexes 30 and 45, respectively, account for 46.4% of all MSSA isolates in the study, suggesting that these two lineages have evolved as extremely successful pandemic colonisers of humans. In conclusion, the overall population structure of American and Dutch nasal carriage isolates of S. aureus is surprisingly similar, despite subtle geographic differences in prevalence of certain S. aureus genotypes.

Published 5 November 2007 in J Clin Microbiol.
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