title: Can chlorination co-select antibiotic-resistance genes?
abstract: Selective pressures, such as chemical or heavy metal pollution, may co-select for bacterial antibiotic resistance in the environment. However, whether chlorination in water treatment can co-select antibiotic-resistant bacteria is controversial. In this study, high capacity quantitative polymerase chain reaction (qPCR) analysis was applied to target almost all known antibiotic-resistance genes (ARGs) (282 types) and 13 mobile genetic elements (MGEs) in bacteria detected in secondary effluents from a municipal wastewater treatment plant after chlorination. The results revealed that 125 unique ARGs were detected in non-chlorinated samples, and the number decreased (79-91 types) as the chlorine concentration was increased. Moreover, 7.49 × 10(4)-3.92 × 10(7) copies/100 ml water reduction of ARGs occurred with 4 mg Cl2/l. Considering the relative abundance of ARGs (i.e., ARG copies normalized to 16S rRNA gene copies), 119 ARGs decreased in response to chlorination, whereas only six ARGs, such as dfrA1, tetPB-03, tetPA, ampC-04, tetA-02, and erm(36), were potentially enriched by 10.90-, 10.06-, 8.63-, 6.86-, 3.77-, and 1.09-fold, respectively. Furthermore, the relative abundance of 12 detected MGEs was lower after chlorination. Therefore, chlorination was effective in reducing ARGs and MGEs rather than co-selecting them.
authors.affiliation: Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Wenfang
authors.initials: W
authors.lastname: Lin
authors.affiliation: Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Menglu
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China.
authors.forename: Shenghua
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China. Electronic address: xyu@iue.ac.cn.
authors.forename: Xin
authors.initials: X
authors.lastname: Yu
mesh_terms: D001419:Bacteria / Q000187:drug effects / Q000235:genetics; D002713:Chlorine / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial; D054879:Halogenation; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D062065:Wastewater / Q000032:analysis / Q000382:microbiology; D018508:Water Purification / Q000379:methods
chemical_list: D002713:Chlorine; D012336:RNA, Ribosomal, 16S; D062065:Wastewater
keywords: Antibiotic-resistance genes; Chlorination; Co-selection; High capacity quantitative PCR analysis; Mobile genetic elements; Water treatment