Community-associated Methicillin-resistant Staphylococcus aureus Isolates and Healthcare-Associated Infections

摘要

We noted a marked increase in healthcare-associated(HA) methicillin-resistant Staphylococcus aureus (MRSA)infections caused by isolates phenotypically consistent withcommunity-associated (CA)-MRSA strains. To study thistrend, we retrospectively examined all HA-MRSA isolatesfrom patients in our institution during 1999–2004. An isolatewas considered an SCCmecIV phenotype if it had antimi-crobial drug susceptibilities consistent with typical CA-MRSA isolates. Our phenotypic definition was validated ina limited subset of isolates by SCCmec genotype, pulsed-field gel electrophoresis, and multilocus sequence typing.Among 352 patients with HA-MRSA isolates, SCCmecIVphenotype increased from 17 in 1999 to 56 in 2003(p<0.0001). Antimicrobial drug-susceptibility phenotypeand genotype were consistent in 21 (91) of 23 isolates. Ina multivariate model, the SCCmec type IV phenotype wasindependently associated with wound culture source, lateryear of collection, and MRSA isolated earlier during hospi-talization. In conclusion, MRSA isolates phenotypically sim-ilar to CA strains have become the predominant isolatesassociated with HA-MRSA in our hospital