Dissemination of Extended-Spectrum Beta-Lactamase–Producing Enterobacteriaceae in an Urban Wastewater Treatment Plant and Their Emission to a River

Abstract

Several studies have reported that wastewater treatment plants may facilitate the occurrence of resistant bacteria in effluents, creating a growing concern about their impact on animal and human health. For this study, 254 Enterobacteriaceae were isolated from influent wastewater, effluent wastewater, and sludge in a municipal wastewater treatment plant and from river water receiving their effluent, with a predominance of Klebsiella pneumoniae. Susceptibility tests showed that amikacine and ciprofloxacine were the most active antibiotics. High resistance rates (>80%) were observed with penicillins and cephalosporins. A set of 143 strains (56.30%) were defined as extended-spectrum beta- lactamase producers. The findings revealed a decrease in the rate of extended-spectrum beta-lactamase (ESBL)–producing Enterobacteriaceae in the effluent wastewater compared to influent wastewater. In addition, nonnegligible levels of these bacteria were found in the river water (17.50%) and sludge (29.41%). This study demonstrated that the municipal sewage may be a reservoir of the dissemination of extended-spectrum beta-lactamase–producing Enterobacteriaceae into the environment, thereby contaminating natural water resources. This survey highlighted the serious negative impact of discharging urban sewage into the environment on public health and suggests that the topic requires further evaluation and appropriate control techniques.