Bacteriological studies on Salmonella infectious diseases caused by Salmonella Oranienburg and Salmonella Chester borne on dried squid

In March 1999, food poisoning from the ingestion of dried squid contaminated with S. Oranienburg and S. Chester spread throughout Japan. To determine the causes leading to the outbreak of S. Oranienburg and S. Chester infections in Ehime prefecture, we screened Salmonella germs isolated for S. Oranienburg and S. Chester from seven hospitals and one clinical laboratory in Ehime prefecture between November 1998 and May 1999. Since June 1999, 18 strains of S. Oranienburg and 6 strains of S. Chester have been isolated in stool specimens from patients with diarrhea, mostly aged 12 years or younger. Three strains were also isolated from blood and urine samples. Isolates from patients and dried squid samples were compared by pulsed-field gel electrophoresis (PFGE) and other epidemiological markers. Biochemical characterization data, drug susceptibility and PFGE patterns of the isolates from the patients and the dried squid samples matched closely. The results of epidemiological and bacteriological studies suggest that the diffuse outbreak of S. Oranienburg and S. Chester infections in Ehime prefecture were caused by the ingestion of contaminated dried squid.