Molecular characterization of Staphylococcus aureus carrying the panton-valentine leucocidin genes in northern Spain

To study the prevalence of the Panton-Valentine leucocidin (PVL) gene in methicillin-susceptible (MSSA) and methicillin-resistant (MRSA) Staphylococcus aureus obtained in Gipuzkoa, northeastern area of the Basque Country, north-central Spain, and perform the molecular characterization of PVL-positive isolates.

Molecular studies comprised: PVL gene detection by PCR, staphylococcal chromosome cassette mec (SCCmec) typing, spa sequencing, multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), and detection of the arginine catabolic mobile element (ACME).

Between 1978 and 2006, only two (0.3%) of the 686 MRSA isolates studied were positive for the PVL gene. This percentage increased between 2007 and 2009, when the PVL gene was detected in 30 of the 679 MRSA (4.4%) and in nine of the 1227 MSSA (0.7%) isolates. The 41 PVL-positive isolates characterized had eight different sequence types (STs). Twenty-three MRSA PVL-positive isolates were ST8, spa type t008, seven of which were ACME positive, erythromycin-resistant and showed the PFGE pattern (90-100% similarity) of the USA300 clone. ST8 was also the most prevalent ST among the nine MSSA PVL-positive isolates.

The current epidemiology of PVL-positive MRSA in our region more closely resembles that of the USA rather than that of other European countries, being USA300 or USA300-like isolates the most prevalent ones.