[Comparison of O-serotype distribution of Escherichia coli isolated from faecal specimens of patients with sporadic diarrhea and healthy persons and regional difference in Japan].

To investigate the isolation frequency of O-serotype of Escherichia coli, a total of 1,563 faecal specimens obtained from patients with sporadic diarrhea in Ishikawa between July 1997 and June 1998, were examined. As a result of O-serotyping of isolated strains using commercially E. coli antisera (43 different types), 247 strains of 29 different O-serotypes were isolated. Isolation rate was 15.8%. Most predominant O-serotype was O1 (128 strains, 52%), followed by O18 (26 strains, 11%), O6 (17 strains, 7%), O111 (16 strains, 6%), and these 4 different O-serotypes took up three quarters of the isolated E. coli. Between August 1996 and May 1997, E. coli isolation from faecal samples of 51,893 healthy persons and O-serotyping of isolated strains using commercial antisera to 6 predominant O-serotypes (O-26, 111, 114, 128, 157 and O1) of VTEC/EHEC were carried out. Among 6 O-serotypes, the most predominant O-serotype was O1 (93% of isolates), followed by O26, 111, 128 (6%) and O114, 157 (1%). These isolation frequencies in patients were 80%, 18%, 2%, respectively, have resembled each other in healthy persons in many points. In a similar way, of these distributions of O-serotype of strains hemolysed on Beutin's blood agar plates, we compared patients with healthy persons. Fifty-six strains (3.6% of the total) of E. coli of different O-serotypes were isolated from 1,563 patients and 57 strains (2.8% of the total) belonging to 11 serotypes from 2,036 healthy persons. As a result of O-serotype frequency, both groups resembled each other. O18 and O6, the most predominant O-serotypes, occupied 64% of the isolated strains in patients and 74% in healthy persons. Next in patients, O1, 26 were 7%--level, O28 ac, 152, 157 were 4%--level, respectively, and in healthy persons. O1 was 5%--level, O28 ac, 55, 146, 152 were 4%--level respectively. In the comparison of O-serotype frequency of E. coli isolated from sporadic diarrhea in other 5 areas (Kanto district, Tokyo, Oita, Aichi and Ishikawa), O1, 6, 8, 18, 25, 26, 55, 86a, 111, 125, 126, 127a, 128, 146, 148, 157 and 166 (17 types) have covered a wide area. On the other hand, O29, 44, 78, 112ac, 115, 136, 143, 152, 168 and 169 (10 types) have a tendency to distribute in local areas, we believe that there are regional differences even in the same Japanese territory.