Characterization of Methicillin-ResistantStaphylococcus aureusIsolates from Portuguese Hospitals by Multiple Genotyping Methods

Abstract

One hundred and eighty-three methicillin-resistant Staphylococcus aureus (MRSA) isolates from eight different Portuguese hospitals were genetically typed by random amplification of polymorphic DNA (RAPD) employing different oligonucleotide primers. Fourteen different RAPD genotypes were identified. A subset of the same strains was also characterized by pulsed-field gel electrophoresis (PFGE) and/or hybridization using mecA and Tn554 probes. In the majority of cases, the different genotyping methods have identified the same MRSA clones. However, PFGE combined with the DNA probes was clearly the method providing higher resolution. Most strains that have already been identified by PFGE and DNA probes as members of the widely spread Iberian clone of MRSA generated a common RAPD genotype. The most prevalent Iberian clone was not detected in a collection of MRSA from Poland that was also examined by RAPD. On the other hand, MRSA strains second most frequent in prevalence in the Portuguese and Polish collection appear to be identical by RAPD, indicating extensive geographic spread of this particular clone. No correlation was apparent between epidemic behavior and the number of protein A gene repeats in this particular collection of MRSA strains.