Nasal swabs were collected from all patients according to an established protocol [16,17]. Samples were sent to two different laboratories of the study area: Laboratori Clínic l’Hospitalet and Laboratori Clínic Bon Pastor. All the S. aureus isolated were tested in a central laboratory (Maastricht University Medical Centre, the Netherlands) for susceptibility to 12 antibiotics assumed to represent a range of commonly used antibiotic classes. The procedure included standardised microdilution tests and classification afterwards (resistant versus susceptible) was based on the breakpoints of the minimum inhibitory concentrations (MIC) of S. aureus defined in the 2017 guidelines of the European Committee on Antimicrobial Susceptibility Testing (EUCAST), published by the European Society of Clinical Microbiology and Infectious Diseases, the European Centre for Disease Prevention and Control and the European national breakpoints committees [17] (Table 1). Breakpoints for S. aureus have not changed since 2011. The genotypic structure of the isolated MRSA strains was established with the spa typing method [10].