Distribution and Diversity of Shiga Toxin 2 Gene in Urban Rivers

Abstract

In urban rivers in Osaka, Japan, DNA containing the stx₂ gene, which encodes the Shiga toxin 2 (Stx₂), was found to be present in sediment, even when it was not detected in the surface water. A DNA sequence similar to that of bacteriophage 933W and the Sakai strain was detected at every sampling location. Two strains of Escherichia coli O157 carrying the stx₂ gene were independently isolated from sediment. These results show that river sediment is a potential reservoir of the stx₂ gene and Shiga toxin-producing bacteria in the natural environment.