Molecular typing of enterohemorrhagic Escherichia coli O157 : H7 isolates derived from an outbreak in Okayama, Japan in 1997 by pulsed-field gel electrophoresis

Thirteen enterohemorrhagic Escherichia coli O157 : H7 (EHEC) isolates derived from the patients of an outbreak in the R-hospital in Okayama Japan and one isolated from the ingredients of Japanese noodles in June 1997 were analyzed by molecular typing using pulsed-field gel electrophoresis (PFGE). The PFGE patterns of the patients were almost the same as the patterns of the Japanese noodle ingredients. Therefore, the EHEC O157 : H7 derived from the food was considered to have caused the outbreak in the R-hospital. The molecular typing of isolates from the patients and the Japanese noodle ingredients was almost the same as that of isolates from outbreaks in Hiroshima and Fukuoka prefectures classified as type Ia in 1996 by PFGE analysis. These results indicate that EHEC O157 : H7 strains with a similar PFGE type Ia pattern have already spread throughout western Japan since last year.