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Ninety-six class 1 integron-positive and 96 integron-negative Escherichia coli isolates cultured from the water of the Warta River, Poland, were characterized for their phylogenetic group affiliation and for the presence of genes associated with virulence. Most strains belonged to phylogenetic group A, but phylogenetic group affiliation was not related with the presence of integrons. The occurrence of heat-stable toxin gene of enterotoxigenic E. coli, S fimbriae subunit gene sfaS, and siderophore receptor genes, fyuA and iutA, was associated with the presence of class 1 integrons. Moreover, virulence factor score (the total number of virulence-associated genes) was associated with the presence of integrons in groups. The results bring new insight into relations between the presence of integrons in E. coli, virulence traits, as well as phylogenetic group affiliation.

In this study, we determined the presence of class 1 integron-integrase gene in culturable heterotrophic bacteria isolated from river water and sediment sampled upstream and downstream of a wastewater treatment plant effluent discharge. Moreover, we quantified intI1 and sulfonamide resistance genes (sul1 and sul2) in the water and sediment using qPCR. There was no correlation between the results from water and sediment samples, which suggests integron-containing bacteria are differentially retained in these two environmental compartments. The discharge of treated wastewater significantly increased the frequency of intI1 among culturable bacteria and the gene copy number in river water, and increased the number of sul1 genes in the sediment. We also observed seasonal differences in the frequency of the class 1 integron-integrase gene among culturable heterotrophs as well as intI1 copy number in water, but not in sediment. The results suggest that the abundance of class 1 integrons in aquatic habitat depends on anthropogenic pressure and environmental factors.Electronic supplementary materialThe online version of this article (doi:10.1007/s00248-016-0843-4) contains supplementary material, which is available to authorized users.