Insufficient decontamination in Sewage treatment plants induce the risk of artificial selection of extended-spectrum β-lactamase producing Escherichia coli.

Quantitative data about extended-spectrum beta-lactamase producing E. coli (ESBLEC) in the wastewaters are scarce, especially in developing countries. These data could be useful to raise awareness about the potential risk of spreading ESBLEC strains in the community. Water samples were collected weekly over a 10-week period, from one urban sewage treatment plant (STP), one rural STP and one hospital complex's wastewater (HWW) in Turkey. Mean E. coli and ESBLEC loads were determined for each sampling point. For the 580 ESBLEC isolated, antimicrobial resistance profiles, phylogenetic grouping, presence of common beta-lactamese-typesand integrons were studied using PCR. The mean ESBLEC ratio was accounted for 0.58%, 0,12%, 1.53% of the total E. coli in urban, rural untreated wastewater and HWW, respectively. These values were higher for the outlets. The mean number of different antimicrobial classes to which the strains were resistant was highest in urban STP (4.0± 1.6). The antimicrobial resistance ratios of ESBLEC strains isolated from HWW were observed to be in between those of urban and rural STPs. The most common phylogenetic group was C composing (29.7%) and the most susceptible strains belonged to phylogroup B1. Wastewater treatments without sufficient decontamination, resulting in artificial selection of ESBLEC might lead to public health risk as these strains reach communities through environment. To avoid such risks and protect the human health as well as the environment, well-established decontamination measures imposing barriers against this artificial selection should be implemented.