Restriction fragment length polymorphisms analysis by pulsed-field gel electrophoresis for discrimination of Staphylococcus aureus isolates from foodborne outbreaks.

A number of outbreaks of disease due to Staphylococcus aureus occurring in Aichi-ken, Japan, have provided the opportunity to investigate aspects of the molecular epidemiology of this and related organisms. Coagulase types, enterotoxin types, phage types, and restriction fragment length polymorphisms (RFLPs) as assessed by pulsed-field gel electrophoresis (PFGE) was performed for S. aureus infections diagnosed in the area of Aichi-ken. Among the 56 isolates of S. aureus from 30 outbreaks, 15 distinctive RFLP types were found by digestion with the restriction enzyme, SmaI. A total of 32 isolates from patients, foodstuffs and cooks on six occasions had the same RFLP types, coagulase types, enterotoxin types and phage types in the same outbreaks. Moreover, the coagulase and phage types could be separated in terms of RFLP. In one outbreak, ten isolates, which were derived from six patients, two foodstuffs and two cooks, had the same coagulase type, enterotoxin type, phage type, and RFLP type. This PFGE method may therefore prove useful for subclassifying S. aureus and differentiating isolates of the same coagulase types and phage types derived from sporadic cases and those derived from foodborne outbreaks.