Staphylococcus aureus in a northern Italian region: Phenotypic and molecular characterization

Staphylococcus aureus is a leading cause of community-acquired infections and healthcare-associated infections.Epidemiological data are useful for understanding the dynamics of the diffusion of this pathogen, and to plan controlactivities and monitor their effi cacy. Methods: S. aureus isolates were collected in 13 public hospital laboratories of Emilia-Romagna (northern Italy region) during February – March 2009; phenotypic and molecular characterizations of these isolateswere performed. Results: The study sample included 267 isolates, 57 from blood, 81 from respiratory tract, and 129from wounds; 106 (40%) were methicillin-resistant S. aureus (MRSA). MRSA showed a limited number of circulating cloneswith 2 predominant spa types – t008 and t041 – accounting for 36% and 27% of MRSA isolates, respectively. The t041 typehad a higher prevalence of antimicrobial resistance compared to other spa types and accounted for most of the retrievedhetero-vancomycin-intermediate S. aureus (h-VISA), while t008 was more frequently detected in non-hospital isolates. Ahigher degree of genetic diversity was observed in methicillin-susceptible S. aureus (MSSA), with no predominant clonesand low prevalence of antimicrobial resistance. The occurrence of community-acquired MRSA infection appears to be rarein Emilia-Romagna. Conclusions: In contrast to previous studies reporting Italian data, t008 was the most frequent spa typeamong MRSA isolates in Emilia-Romagna. The prevalence of antimicrobial resistance of different MRSA spa types couldinfl uence their ability to cause infections with hospital onset. The presence of only 2 major MRSA clones circulating inEmilia-Romagna increases the chances that a regional strategy aimed at MRSA prevention will be effective