title: Sewage treatment plant serves as a hot-spot reservoir of integrons and gene cassettes.
abstract: This study investigated the occurrence and abundance of class 1 integrons and related antibiotic resistance genes (ARGs) in a sewage treatment plant (STP) of China. Totally, 189 bacterial strains were isolated from influent, activated sludge and effluent, and 40 isolates contained the integons with a complete structure. The intl1-carrying isolates were found to harbor two types of gene cassettes: dfr17-aadA5 and aadA2, conferring resistances to trimethoprim and streptomycin, which were further confirmed by antimicrobial susceptibility analysis. Many other gene cassettes were carried on integron, including qnrVC1, catB-8-blaoxa-10-aadA1-aac(6'), aadB-aacA29b, aadA2, aac(6')-1b, aadA6 and aadA12, which were detected using DNA cloning. Quantitative real time PCR showed that over 99% of the integrons was eliminated in activated sludge process, but average copy number of integrons in given bacterial cells was increased by 56% in treated sewage. Besides integrons, other mobile gene elements (MGEs) were present in the STP with high abundance. MGEs and the associated ARGs may be wide-spread in STPs, which constitute a potential hot spot for selection of antibiotic resistant bacteria and horizontal transfer of ARGs.
authors.forename: Liping
authors.initials: L
authors.lastname: Ma
authors.forename: Xu-Xiang
authors.initials: XX
authors.lastname: Zhang
authors.forename: Fuzheng
authors.initials: F
authors.lastname: Zhao
authors.forename: Bing
authors.initials: B
authors.lastname: Wu
authors.forename: Shupei
authors.initials: S
authors.lastname: Cheng
authors.forename: Liuyan
authors.initials: L
authors.lastname: Yang
mesh_terms: D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D032023:Integrons / Q000502:physiology*; D012722:Sewage / Q000382:microbiology*; D014865:Waste Disposal, Fluid / Q000379:methods*; D014871:Water Microbiology; D014873:Water Pollutants
chemical_list: D004269:DNA, Bacterial; D012722:Sewage; D014873:Water Pollutants