One-year surveillance of methicillin-resistant Staphylococcus aureus in health-care setting, Palermo, Italy

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging cause of infections outside of health care settings. We carried out a survey to determine the prevalence and characteristics of MRSA isolates (CA-MRSA, HA-MRSA) identified among in- and outpatients by the clinical microbiology laboratories of four general hospitals in Palermo, Italy during the period February-January 2010. Methods: Participating laboratories performed isolation, confirmed methicillin-resistance by their routine method and weekly sent their strains to the coordinating laboratory at the Department of Sciences for Health Promotion “G. D’Alessandro”, University of Palermo, Italy. The isolates were test for antimicrobial susceptibility by E-test and using the disk diffusion test. Presence of the mecA gene was investigated by PCR using primers and standard conditions. Multiplex PCR was performed to determine SCCmec types I to V.9 Strains assigned to SCCmec type IVa were submitted to polymerase chain reaction (PCR) for detection of the Panton-Valentine leukocidin toxin genes lukS-PV and lukF-PV. Multiple-locus variable-number tandem-repeat analysis (MLVA) was performed. Pulsed field gel electrophoresis (PFGE) was performed as previous reported. Multilocus sequence typing (MLST) was performed on the MRSA strains following the recommended procedure at the S. aureus MLST. Results: we collected 227 isolates from 185 patients. The distribution of MRSA from different wards was: intensive-care 25%, surgery 20%, internal medicine 33%, other 15,5% unknown 6,5%. 69% of MRSA strains were resistant to ciproflox and/or levofloxacin, 40% to macrolide and 38% to gentamycin. SCCmec type IVa has been found in 42 isolates from hospitalized patients. PFGE analysis showed 81 MLVA different banding patterns. Strains of MRSA ST398 were found. Conclusions: Detect circulation of MRSA clinically relevant strains through surveillance, timely hygienic interventions and cooperation by health care personnel are crucial to minimize or control health care-associated infections. The changing epidemiology of MRSA indicates that collaborative surveillance plans integrating human and animal information should be increased.