[Clinical epidemiology of nosocomial MRSA infections].

We have compared genomic DNA fingerprinting patterns among isolates of methicillin-resistant Staphylococcus aureus (MRSA) by using pulsed-field gel electrophoresis (PFGE). Chromosomal fragment profiles digested with Sma I were most suitable for discriminating between isolates which could not be differentiated by phenotypic methods. We also constructed a typing system for MRSA strains on the basis of the macrorestriction analysis by PFGE. A total of 563 strains of MRSA were collected from all of the 43 national university hospitals in Japan. Based on the gel profiles, 136 types were identified. Genotyping by the DNA fingerprinting patterns is proposed as a useful method for study of the epidemiology on nosocomial infections caused by MRSA.