[Genomic DNA fingerprinting by pulsed-field gel electrophoresis for study of nosocomial infection caused by methicillin-resistant Staphylococcus aureus].

In this study, we have compared genomic DNA fingerprintings among isolates of methicillin-resistant Staphylococcus aureus (MRSA) by using pulsed-field gel electrophoresis (PFGE). Chromosomal fragments digested with Sma I were most suitable for the PFGE separation, giving 15-20 fragments of sizes ranging from about 30-1,500 kb. Thirty-one distinctive fragment patterns were identified in 111 isolates of MRSA. On the basis of the genomic typing by PFGE, we performed an epidemiological investigation of an outbreak of nosocomial MRSA infection among 18 inpatients in Nagoya University Hospital. Ten types of chromosomal digestion were identified in 21 isolates of MRSA. The clarity and polymorphism of the chromosomal digestion patterns enabled us to discriminate between isolates. Classification of the genomic DNA fingerprinting patterns by PFGE is therefore proposed as a useful method for investigating the source, transmission, and spread of nosocomial MRSA infections.