Molecular epidemiology of community-associated methicillin-resistant Staphylococcus aureus in Spain: 2004-12

Abstract

Objectives: In Spain, despite the high rates of healthcare-associated methicillin-resistant Staphylococcus aureus (MRSA), the incidence of community-associated (CA) MRSA seems to be low on the basis of a small number of studies. We analysed the evolution of CA-MRSA in Spain from 2004 to 2012, and identified the clonal lineages and population structure.

Methods: The study included 8326 MRSA strains. Susceptibility to 18 antimicrobials was determined. Isolates were tested for the presence of mecA, Panton-Valentine leucocidin (PVL) and the arginine catabolic mobile element (ACME) by PCR, and typed by staphylococcal cassette chromosome mec, PFGE, spa, multilocus sequence typing and agr.

Results: Among the 8326 isolates, 246 (2.9%) were CA-MRSA. We identified genotypically 226 PVL-positive CA-MRSA isolates (88% agr type I, 10.2% agr type III and 1.8% agr type II) and 20 PVL-negative CA-MRSA isolates (all agr type I) from children and adults (82.1% from wounds) from 13 different geographical areas. A significant increase in the rates of CA-MRSA was observed when comparing 2004-07 (0.43%) with 2008-12 (5.44%). Resistance rates were as follows: only β-lactams, 84.5%; erythromycin, 12.8%; tetracycline, 8.8%; clindamycin, 4.9%; ciprofloxacin, 3.1%; fusidic acid, 2.0%; others, 0.4%; and multiresistant, 6.2% (six isolates USA300). The strains belonged to the PVL-positive clones ST8-IVc (69.9%), ST8-IVa-ACME-positive (USA300, 8.9%), ST8-IVa-ACME-negative (0.8%), ST30-IVc (4.5%), ST80-IVc (2.0%), ST5-IVc (1.2%) and others (ST59, ST72, ST88, ST642, ST1472 and ST1829; 4.5%) and to the PVL-negative ST398-V (8.1%).

Conclusions: We confirm an increase in CA-MRSA in Spain, the predominance of the ST8-IVc clone, the emergence of the USA300 clone, a high genetic diversity among PVL-positive CA-MRSA isolates and the recent emergence of the pig-associated ST398-V clone.

Keywords: MRSA; PVL; ST398; community-associated MRSA; linezolid; livestock-associated MRSA; skin and soft-tissue infections.