Staphylococcus aureus in a northern Italian region: phenotypic and molecular characterization.

BACKGROUND: 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 control activities and monitor their efficacy. 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 isolates were performed. RESULTS: The study sample included 267 isolates, 57 from blood, 81 from respiratory tract, and 129 from wounds; 106 (40%) were methicillin-resistant S. aureus (MRSA). MRSA showed a limited number of circulating clones with 2 predominant spa types--t008 and t041--accounting for 36% and 27% of MRSA isolates, respectively. The t041 type had a higher prevalence of antimicrobial resistance compared to other spa types and accounted for most of the retrieved hetero-vancomycin-intermediate S. aureus (h-VISA), while t008 was more frequently detected in non-hospital isolates. A higher degree of genetic diversity was observed in methicillin-susceptible S. aureus (MSSA), with no predominant clones and low prevalence of antimicrobial resistance. The occurrence of community-acquired MRSA infection appears to be rare in Emilia-Romagna. CONCLUSIONS: In contrast to previous studies reporting Italian data, t008 was the most frequent spa type among MRSA isolates in Emilia-Romagna. The prevalence of antimicrobial resistance of different MRSA spa types could influence their ability to cause infections with hospital onset. The presence of only 2 major MRSA clones circulating in Emilia-Romagna increases the chances that a regional strategy aimed at MRSA prevention will be effective.

Accuracy of automated and manual systems for susceptibility testing of Pseudomonas aeruginosa to piperacillin and piperacillin-tazobactam.

This study aimed to evaluate the accuracy of routine systems (Vitek2 cards AST-N022 and AST-N026; Kirby Bauer; Etest) for susceptibility testing of Pseudomonas aeruginosa to piperacillin and piperacillin-tazobactam. Vitek2 (card AST-N022) showed the worst performance; the other three methods (Vitek2 card AST-N026, Kirby-Bauer and E-test) performed comparably but never fulfilled the minimal standard proposed by FDA.