Carbapenem-resistant bacteria over a wastewater treatment process: Carbapenem-resistant Enterobacteriaceae in untreated wastewater and intrinsically-resistant bacteria in final effluent

Abstract Although urban wastewater treatment plants (UWWTPs) are important sites for antibiotic resistance elimination, their limitation in producing resistance-free effluents is recognized. Despite the critical importance of carbapenems to human health, the fate and diversity of carbapenem-resistant bacteria (CRB) in UWWTPs is still poorly understood. We analysed CRB from different treatment stages in a UWWTP applying UV-C radiation. After secondary treatment, bacteria grown in mFC medium reduced in 1.9-log units (p  UV-C radiation significantly reduced the abundance and prevalence of CRB. Bacteria intrinsically-resistant to carbapenems were cultivated after all treatment stages, while CRE only in raw wastewater. In these samples, we detected CRE with blaGES-5, in integrons and plasmids. This raises concern as horizontal gene transfer may occur within these systems. Carbapenem resistance surveillance in UWWTPs is essential to implement mitigation measures in a timely manner.