COMBINED USE OF BACTERIOPHAGE-TYPING AND PULSED-FIELD GEL-ELECTROPHORESIS IN THE EPIDEMIOLOGIC ANALYSIS OF JAPANESE ISOLATES OF ENTEROHEMORRHAGIC ESCHERICHIA-COLI O157-H7

A total of 236 enterohemorrhagic Escherichia coli (EHEC) O157:H7 isola tes in Japan were investigated by bacteriophage typing, and the result s were compared with those of pulsed-field gel electrophoresis (PFGE), Seven phage types (PTs) were observed in 71 isolates which were deriv ed from 22 outbreaks. All of the isolates from ten outbreaks in the Ki nki region (midwestern part of Japan) in July-August 1996 were grouped into the same PFGE type (IIa) and PT 32, while among total isolates, there were such varieties as PFGE type IIa containing five phage types and PT32 containing two PFGE types. These results suggest that the te n outbreaks should be considered to be a single outbreak, and show tha t the combined use of bacteriophage typing and PFGE enhances reliabili ty in epidemiological surveys.