Surveillance of methicillin-resistant Staphylococcus aureus isolated in Torino (northwest Italy)

Abstract

Nosocomial infections by methicillin-resistant Staphylococcus aureus (MRSA) are an increasing cause of morbidity and mortality. Recently, a worldwide increase of community-acquired MRSA infections has also been recorded. The purpose of this study was to assess the frequency of MRSA isolation from in- and outpatients admitted to an academic teaching hospital near Torino (northwest Italy) in 1 year and to characterize 90 clinical isolates of MRSA collected in the same period. Antimicrobial susceptibility and the presence in the isolates of the Panton–Valentine leukocidin (PVL) gene were assessed. Molecular epidemiology was performed by SCC mec and capsule typing, and by pulsed-field gel electrophoresis. The global proportion of MRSA isolated was 33.1%. Characterization performed on 90 MRSA revealed a high percentage of resistance to ciprofloxacin and erythromycin, and the presence of the PVL gene in one strain only. Most of the MRSA strains circulating in the Torino district belonged to SCC mec types II and I, and the 67.6% resulted positive for the cap 5 gene. The pulsotype analysis permitted to observe a clonal heterogeneity of the isolates and a higher similarity in relation to singular mec types; only few nosocomial clones could account for a local outbreak of a sporadic isolate.