Application of small fragment restriction endonuclease analysis (SF-REA) to the epidemiological fingerprinting of Staphylococcus aureus.

Total cell DNA of 14 isolates of Staphylococcus aureus from patients of an intensive care unit (ICU) and 180 unrelated strains was examined by restriction endonuclease analysis (REA). EcoRI-generated DNA fragments were either subjected to conventional REA on agarose gels and stained with ethidium bromide or separated by polyacrylamide gel electrophoresis and visualised by silver staining (SF-REA). Both methods were compared for inter-strain discriminatory ability, reproducibility and handling. All DNA-cleavage patterns of unrelated strains clearly differed from each other when subjected to SF-REA. In contrast, all S. aureus isolates from the ICU gave identical restriction fragment patterns. These findings supported the suspicion of nosocomial infection in these patients. Conventional REA proved the identity of the ICU isolates, but it failed to differentiate between some of the unrelated strains. Therefore SF-REA of total cell DNA seemed to be superior. It has proved to be a very useful technique for studying the epidemiology of S. aureus in hospitals.