Methicillin-resistantMethicillin-resistant Staphylococcus aureus (MRSA) infections have been recognized for decades as hospital acquired or healthcare associated (2,6,20). Nowadays, MRSA is also recognized as a worldwide emerging community-acquired pathogen (CA-MRSA) (5, 30, 32). CA-MRSA generally causes primary skin and soft tissue infections, such as furunculosis and abscesses, but necrotizing tissue infections and lethal hemorrhagic pneumonia, even in previously healthy individuals, have recently been described as well (5, 21). Most CA-MRSA strains have a common virulence factor: Panton-Valentine leucocidin (PVL) (8,9,13,27). CA-MRSA infections spread easily by direct skin-to-skin contact. Outbreaks in closed living communities, as with jail inmates, military recruits, and gay men, have been reported in the United States (16,26,28). The spread of PVL-positive S. aureus has also been described within families (25) and among healthcare staff (31).In 2003 Due to the implementation of successful search-and-destroy guidelines, the incidence of MRSA in The Netherlands is very low (Ͻ1% in Dutch hospitals). Nevertheless, analysis of MRSA strains obtained from the Dutch MRSA surveillance program showed the presence of the PVL genes in MRSA with diverse STs (34). In this study, we have characterized 197 MRSA isolates randomly chosen from the national collection in The Netherlands. The PVL genes were detected in 5 of the 99 isolates (5%) collected in 2000 and in 15 of the 98 isolates (15%) collected in 2002. The genetic characteristics of the PVL-positive MRSA isolates were compared with those observed in other countries and continents.
MATERIALS AND METHODSGeneral setting and organization of the survey. The National Institute of Public Health and the Environment (RIVM) serves as the national reference center for surveillance of MRSA in The Netherlands. On behalf of the Dutch Health Inspectorate, each hospital is requested to send all first clinical MRSA isolates from sporadic infections and from nosocomial outbreaks to the RIVM for confirmation and further typing.Bacterial isolates. To estimate the prevalence of PVL-positive MRSA in The Netherlands, MRSA isolates were randomly chosen from the RIVM national MRSA surveillance collection for two periods of time: (i) for the period 1987 through 1995, 216 isolates were selected from a collection of 1,768 MRSA isolates; (ii) for the years 2000 and 2002, 99 and 98 MRSA isolates, respectively, were selected from a collection of 1,590 MRSA isolates. Identification of MRSA was confirmed by mecA PCR assay (12), Martineau PCR assay for species identification (22), and oxacillin susceptibility testing by E-test on MuellerHinton agar plus 2% NaCl with 24 h of incubation at 35°C (interpretation criteria were used according to the guidelines of the CLSI [formerly NCCLS]) (23).