Fate and behavior of extended-spectrum β-lactamase-producing genes in municipal sewage treatment plants

Abstract

Extended-spectrum β-lactamases (ESBLs) have the capability of hydrolyzing a variety of the newer β-lactam antibiotics, including the third-generation cephalosporins and monobactams known as a rapidly evolving group of ESBLs. The purpose of this study was to investigate the occurrence and fate of β-lactamase producing genes (CTX-M type 1, type2, CTX-M probe for all groups except CTX-M-1, and TEM, SHV, OXA) through wastewater treatment utilities. β-lactamase producing genes in influent, digested sludge, activated sludge, and disinfected effluent were monitored. The results showed that influent contained high level of all target genes, and all CTX-M types, SHV, and OXA gene decreased significantly in biological treatment process such as activated sludge process and anaerobic digestion, however, TEM type was not effectively eliminated. Possibly, host microbes of TEM could be most resistant in target genes or to some extent gene transfer occurred in wastewater treatment processes. All target genes were significantly reduced during disinfection. Consequently, wastewater treatment process apparently reduced host microbes carrying β-lactamase producing genes effectively, although they are selectively removed in biological processes. In addition, the significant reduction during disinfection was shown, although slightly differences of removal efficiency were observed in resistance.