Abstract
Serotypes and distribution of the virulence genes of Escherichia coli isolates from healthy individuals were investigated. Four-hundred and 38 E. coli strains, from 428 (9.2%) of 4,667 individuals, were serotypable by using of the commercially available serotyping serum, and those E. coli strains were classified into 37 O serotypes, 20 H and 118 OH serotypes. The most frequent O serotype was O1 (32.3%), followed by O18 (15.9%). The virulence genes (it, st, stx, eaeA, invE, aggR, and astA) were detected in 75 (17.1%) out of 438 strains. Only two strains of O1 and O18 serotypes had the virulence genes. In antibiotic sensitivity tests for 12 drugs, 29 diarrheagenic E. coli strains were resistant, especially all 24 strains harboring aggR were resistant to ABPC. It is risky that the screening by serotyping can also cover non-pathogenic E. coli from our results. The precise screening for the virulence factors by PCR after the screening by serotyping against the diarrheagenic E. coli isolates is important. For some virulence factors, eaeA and astA, which are uncertain in the relationship with serotypes, I should make clear their distribution pattern and the relationship with serotypes in the diarrheagenic E. coli isolates in future.
