Community-acquired methicillin-resistant Staphylococcus aureus clones circulating in Belgium from 2005 to 2009: changing epidemiology

The present study reports the evolution of the demographic characteristics and the molecular epidemiology of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) in Belgium from 2005 to 2009. Four hundred and ten CA-MRSA isolates were prospectively collected and screened for the presence of Panton-Valentin leucocidin (PVL) and toxic shock syndrome toxin 1 (TSST-1) encoding genes, while clinical information were recorded. PVL- and TSST-1-positive isolates were genotyped by pulsed-field gel electrophoresis (PFGE). Staphylococcal cassette chromosome mec (SCCmec) type, spa type and multilocus sequence type (MLST) were determined on representative isolates. One hundred and fifty-nine (39 %) isolates were PVL-positive. PVL-positive isolates were significantly more frequently isolated from skin or soft tissue than PVL-negative isolates, causing mainly subcutaneous abscesses and furuncles. Patients with PVL-positive CA-MRSA were significantly younger than patients with PVL-negative CA-MRSA. Eighty-seven percent of the PVL-positive isolates belonged to a limited number (n = 7) of PFGE types belonging to sequence types (ST) ST80, ST8, ST30, ST5, ST152, ST338 and a new ST, a single-locus variant of ST1. A temporal evolution of the distribution of these PFGE types was observed, characterised by (1) the dissemination of the ST8-SCCmecIV arcA-positive (USA300) genotype and (2) a genetic diversification. Forty-seven (11 %) strains were TSST-1-positive, of which 65 % clustered into four PFGE types, all belonging to ST5. The epidemiology of CA-MRSA in Belgium is changing, as the rapid diffusion of the USA300 clone seems to occur, together with a clonal diversification.