The surface river water and clinical Escherichia coli isolates: characteristics, diversity and epidemiological significance

Using selective media for coliform bacteria, 487 isolates in total were obtained from five different sites of Danube and Morava river waters in and near to Bratislava metropolitan area from February to October during one year. The fifty-six randomly chosen representatives from 396 of these strains identified as Escherichia coli, on the basis of biochemical tests, and forty clinical E. coli strains isolated from patients with urinary disease, were further analysed. Most of isolates were resistant to one or more drugs belonging to different classes of antibiotics. Electrophoresis of outer membrane proteins diversified fifty-six river water isolates into 33 patterns, while corresponding figure for clinical strains was 19 patterns. Single protein membrane patterns were assigned to single bacterial clones. The results revealed the relationships between origin of bacterial clones and sample sites and/or sample times. The isolates also differed with regard to plasmid contents so that natural samples were represented by 28, and clinical isolates by 13 patterns. Both outer membrane protein patterns and plasmid patterns showed higher genetic variability inside the river water and inside the clinical strains. The presence of conjugative plasmid(s) in E. coli cells indicated horizontal gene transfer inside the E. coli populations within bacterial assemblages. Confirmation of the presence of stx2A gene carried on plasmid(s) inside clinical strains suggested the occurrence of Shiga toxin-producing E. coli (STEC) strains. The presence of stx2A gene in surface water of Danube river suggested the occurrence of some of Stx-producing bacterial strains, perhaps some representatives of enterohemorrhagic E. coli (EHEC). The epidemiological significance of Danube river water, and diagnostic samples were also discussed with regard to the occurrence of pathogenic E. coli strains in these samples, where they may pose a risk to human health