Prevalence and resistance of commensal Staphylococcus aureus, including meticillin-resistant S aureus, in nine European countries: a cross-sectional study.

Background: Information about the prevalence of Staphylococcus aureus resistance to antimicrobial drugs has mainly been obtained from invasive strains, although the commensal microbiota is thought to be an important reservoir of resistance. We aimed to compare the prevalence of nasal S aureus carriage and antibiotic resistance, including meticillin-resistant S aureus (MRSA), in healthy patients across nine European countries.

Methods: In this cross-sectional study, nasal swabs were obtained from 32,206 patients recruited by family doctors participating in existing nationwide family doctor networks in Austria, Belgium, Croatia, France, Hungary, Spain, Sweden, the Netherlands, and the UK. Eligible patients were aged 4 years or older (≥ 18 years in the UK) and presented with a non-infectious disorder. Swabs were sent to national microbiological laboratories for identification and isolation of S aureus. Antibiotic resistance testing was done at one central microbiological laboratory. We established the genotypic structure of the isolated MRSA strains with the spa typing method.

Findings: S aureus was isolated from 6956 (21 · 6%) of 32,206 patients swabbed. The adjusted S aureus prevalence for patients older than 18 years ranged from 12 · 1% (Hungary) to 29 · 4% (Sweden). Except for penicillin, the highest recorded resistance rate was to azithromycin (from 1 · 6% in Sweden to 16 · 9% in France). In total, 91 MRSA strains were isolated, and the highest MRSA prevalence was reported in Belgium (2 · 1%). 53 different spa types were detected-the most prevalent were t002 (n = 9) and t008 (n = 8).

Interpretation: The prevalence of S aureus nasal carriage differed across the nine European countries assessed, even after correction for age, sex, and family doctor. Generally, the prevalence of resistance, including that of MRSA, was low. The MRSA strains recorded showed genotypic heterogeneity, both within and between countries.

Funding: European Commission, 7th Framework Programme(grant agreement 223083).