Molecular epidemiology of enterococci with high-level resistance to aminoglycosides.

ABSTRACT

DNA-based methodologies are considerably more powerful than other phenotype-based typing systems, providing a finer level of epidemiological discrimination, differentiating both closely and distantly related independent isolates that otherwise may appear as identical. In this study, plasmid analysis and pulsed-field gel electrophoresis were used to compare 28 isolates of Enterococci (respectively 13 strains of Enterococcus faecalis and 15 strains of Enterococcus faecium) with high-level resistance to aminoglycosides, isolated in Catania (Italy). Plasmid profile analysis resolved 20 different patterns among 24 plasmid harboring strains; many isolates showed one or two plasmids of the same size, but different plasmid content. Analysis of the PFGE-based RFLP patterns after SmaI digestion of genomic DNA resolved 26 different clones from 28 isolates particularly, it resolved two different clones from three isolates showing identical plasmid profiles, and it identified as a single clone two isolates exhibiting different plasmid profiles. Thus, on the basis of our PFGE-based RFLP analysis data, we concluded that all the strains included in the study were genetically unrelated with two exceptions.