A COMBINED MOLECULAR APPROACH TO SCREEN FOR MEC GENE VARIANTS FROM METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS

Previous reports have suggested a common origin for all methicillin re sistance (mec) genes from methicillin-resistant Staphylococcus aureus (MRSA) isolates examined so far. The purpose of this study was to expl ore several molecular methods for screening MRSA isolates from differe nt sources and, in some cases, with varying phenotypes. Eighty MRSA is olates from three teaching hospitals in the University of Louisville M edical Center were compared with MRSAs from a hospital in southern Cal ifornia and with methicillin-sensitive S. aureus isolates. The methods were used to detect the presence of mec gene and to screen for any po lymorphisms in these genes for the respective strains. The mec gene fo r each isolate was amplified via the polymerase chain reaction, and ea ch polymerase chain reaction product was compared to the others by res triction enzyme digestion, denaturing-gradient gel electrophoresis, an d mutation detection enhancement. By these criteria, the mec genes fro m the 80 MRSA strains in this study seemed to be identical. Such a fin ding was not unexpected and supported the existing hypothesis of a com mon ancestor for all mec genes isolated in MRSA isolates. However, the combination of methods used in this study may facilitate screening of MRSA strains in population studies as mec gene variants begin to emer ge. (C) 1998 Elsevier Science Inc.