title: Minimal selective concentrations of tetracycline in complex aquatic bacterial biofilms.
abstract: Selection pressure generated by antibiotics released into the environment could enrich for antibiotic resistance genes and antibiotic resistant bacteria, thereby increasing the risk for transmission to humans and animals. Tetracyclines comprise an antibiotic class of great importance to both human and animal health. Accordingly, residues of tetracycline are commonly detected in aquatic environments. To assess if tetracycline pollution in aquatic environments promotes development of resistance, we determined minimal selective concentrations (MSCs) in biofilms of complex aquatic bacterial communities using both phenotypic and genotypic assays. Tetracycline significantly increased the relative abundance of resistant bacteria at 10 μg/L, while specific tet genes (tetA and tetG) increased significantly at the lowest concentration tested (1 μg/L). Taxonomic composition of the biofilm communities was altered with increasing tetracycline concentrations. Metagenomic analysis revealed a concurrent increase of several tet genes and a range of other genes providing resistance to different classes of antibiotics (e.g. cmlA, floR, sul1, and mphA), indicating potential for co-selection. Consequently, MSCs for the tet genes of ≤ 1 μg/L suggests that current exposure levels in e.g. sewage treatment plants could be sufficient to promote resistance. The methodology used here to assess MSCs could be applied in risk assessment of other antibiotics as well.
authors.affiliation: Department of Infectious Diseases, Institute for Biomedicine, Sahlgrenska Academy, University of Gothenburg, Sweden.
authors.forename: Sara V
authors.initials: SV
authors.lastname: Lundström
authors.affiliation: Department of Chemistry, Umeå University, Sweden.
authors.forename: Marcus
authors.initials: M
authors.lastname: Östman
authors.affiliation: Department of Infectious Diseases, Institute for Biomedicine, Sahlgrenska Academy, University of Gothenburg, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Bengtsson-Palme
authors.affiliation: Department of Infectious Diseases, Institute for Biomedicine, Sahlgrenska Academy, University of Gothenburg, Sweden.
authors.forename: Carolin
authors.initials: C
authors.lastname: Rutgersson
authors.affiliation: Department of Infectious Diseases, Institute for Biomedicine, Sahlgrenska Academy, University of Gothenburg, Sweden.
authors.forename: Malin
authors.initials: M
authors.lastname: Thoudal
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, Sweden.
authors.forename: Triranta
authors.initials: T
authors.lastname: Sircar
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, Sweden.
authors.forename: Hans
authors.initials: H
authors.lastname: Blanck
authors.affiliation: Department of Shipping and Marine Technology, Chalmers University of Technology, Sweden.
authors.forename: K Martin
authors.initials: KM
authors.lastname: Eriksson
authors.affiliation: Department of Chemistry, Umeå University, Sweden.
authors.forename: Mats
authors.initials: M
authors.lastname: Tysklind
authors.affiliation: Department of Infectious Diseases, Institute for Biomedicine, Sahlgrenska Academy, University of Gothenburg, Sweden.
authors.forename: Carl-Fredrik
authors.initials: CF
authors.lastname: Flach
authors.affiliation: Department of Infectious Diseases, Institute for Biomedicine, Sahlgrenska Academy, University of Gothenburg, Sweden. Electronic address: joakim.larsson@fysiologi.gu.se.
authors.forename: D G Joakim
authors.initials: DGJ
authors.lastname: Larsson
mesh_terms: D001419:Bacteria; D018441:Biofilms / Q000254:growth & development*; D004352:Drug Resistance, Microbial / Q000235:genetics; D004784:Environmental Monitoring; D013752:Tetracycline / Q000032:analysis*; D013753:Tetracycline Resistance / Q000235:genetics; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D013752:Tetracycline
keywords: Antibiotic contaminants; Antibiotic resistance; Environmental emission limits; Minimal selective concentration; Risk assessment