title: Abundances of tetracycline, sulphonamide and beta-lactam antibiotic resistance genes in conventional wastewater treatment plants (WWTPs) with different waste load.
abstract: Antibiotics and antibiotic resistant bacteria enter wastewater treatment plants (WWTPs), an environment where resistance genes can potentially spread and exchange between microbes. Several antibiotic resistance genes (ARGs) were quantified using qPCR in three WWTPs of decreasing capacity located in Helsinki, Tallinn, and Tartu, respectively: sulphonamide resistance genes (sul1 and sul2), tetracycline resistance genes (tetM and tetC), and resistance genes for extended spectrum beta-lactams (blaoxa-58, blashv-34, and blactx-m-32). To avoid inconsistencies among qPCR assays we normalised the ARG abundances with 16S rRNA gene abundances while assessing if the respective genes increased or decreased during treatment. ARGs were detected in most samples; sul1, sul2, and tetM were detected in all samples. Statistically significant differences (adjusted p<0.01) between the inflow and effluent were detected in only four cases. Effluent values for blaoxa-58 and tetC decreased in the two larger plants while tetM decreased in the medium-sized plant. Only blashv-34 increased in the effluent from the medium-sized plant. In all other cases the purification process caused no significant change in the relative abundance of resistance genes, while the raw abundances fell by several orders of magnitude. Standard water quality variables (biological oxygen demand, total phosphorus and nitrogen, etc.) were weakly related or unrelated to the relative abundance of resistance genes. Based on our results we conclude that there is neither considerable enrichment nor purification of antibiotic resistance genes in studied conventional WWTPs.
authors.affiliation: Institute of Technology, University of Tartu, Tartu, Estonia.
authors.forename: Mailis
authors.initials: M
authors.lastname: Laht
authors.affiliation: Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland.
authors.forename: Antti
authors.initials: A
authors.lastname: Karkman
authors.affiliation: Institute of Technology, University of Tartu, Tartu, Estonia.
authors.forename: Veiko
authors.initials: V
authors.lastname: Voolaid
authors.affiliation: Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Christian
authors.initials: C
authors.lastname: Ritz
authors.affiliation: Institute of Technology, University of Tartu, Tartu, Estonia.
authors.forename: Tanel
authors.initials: T
authors.lastname: Tenson
authors.affiliation: Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland.
authors.forename: Marko
authors.initials: M
authors.lastname: Virta
authors.affiliation: Institute of Technology, University of Tartu, Tartu, Estonia.
authors.forename: Veljo
authors.initials: V
authors.lastname: Kisand
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects / Q000235:genetics; D004352:Drug Resistance, Microbial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013449:Sulfonamides / Q000494:pharmacology*; D013752:Tetracycline / Q000494:pharmacology*; D013753:Tetracycline Resistance / Q000235:genetics; D014865:Waste Disposal, Fluid; D062065:Wastewater / Q000382:microbiology*; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D012336:RNA, Ribosomal, 16S; D013449:Sulfonamides; D013752:Tetracycline; D062065:Wastewater; D047090:beta-Lactams
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