Polyclonal presence of non-multiresistant methicillin-resistant Staphylococcus aureus isolates carrying SCC mec IV in health care-associated infections in a hospital in Rio de Janeiro, Brazil

Abstract

Change in epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) was observed because of the emergence of infections by non-multiresistant MRSA (nMRSA) in our hospital in Rio de Janeiro, Brazil. Clinical characterization and molecular analysis of 20 nMRSA isolates recovered from 17 patients, between February 2005 and March 2006, were performed. The analysis included SCC mec (staphylococcal cassette chromosome mec), pulsed field gel electrophoresis (PFGE), multilocus restriction fragment, and multilocus sequence typing. MICs for oxacillin and vancomycin and presence of Panton–Valentine leukocidin (PVL) genes were also investigated. All but 1 of the 20 isolates presented SCC mec type IV. PFGE clustered all isolates into 9 genotypes. MIC ≤16 μg/mL to oxacillin was found for 65% of the isolates, whereas 80% exhibited MIC of 2 μg/mL for vancomycin. PVL-encoding genes were observed in 3 isolates. Polyclonal presence of nMRSA SCC mec IV was observed in our institution, including community and health care-associated isolates, which belonged to the sequence types (STs) 1 (clonal complex [CC1]), ST5 (CC5), ST8 and ST72 (CC8), ST97 (CC97), and 2 ST singletons (SLV5 and SLV30).