title: Antibiotic Resistance Genes in Freshwater Biofilms May Reflect Influences from High-Intensity Agriculture.
abstract: Antibiotic resistance is a major public health concern with growing evidence of environmental gene reservoirs, especially in freshwater. However, the presence of antibiotic resistance genes in freshwater, in addition to the wide spectrum of land use contaminants like nitrogen and phosphate, that waterways are subjected to is inconclusive. Using molecular analyses, freshwater benthic rock biofilms were screened for genes conferring resistance to antibiotics used in both humans and farmed animals (aacA-aphD to aminoglycosides; mecA to ß-lactams; ermA and ermB to macrolides; tetA, tetB, tetK, and tetM to tetracyclines; vanA and vanB to glycopeptides). We detected widespread low levels of antibiotic resistance genes from 20 waterways across southern New Zealand throughout the year (1.3 % overall detection rate; 480 samples from three rocks per site, 20 sites, eight occasions; July 2010-May 2011). Three of the ten genes, ermB, tetK, and tetM, were detected in 62 of the 4800 individual screens; representatives confirmed using Sanger sequencing. No distinction could be made between human and agricultural land use contamination sources based on gene presence distribution alone. However, land use pressures are suggested by moderate correlations between antibiotic resistance genes and high-intensity farming in winter. The detection of antibiotic resistance genes at several sites not subject to known agricultural pressures suggests human sources of resistance, like waterway contamination resulting from unsatisfactory toilet facilities at recreational sites.
authors.affiliation: Department of Zoology, University of Otago, PO Box 56, Dunedin, 9054, New Zealand. cynthia.winkworth@gmail.com.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Winkworth-Lawrence
authors.affiliation: Department of Zoology, University of Otago, PO Box 56, Dunedin, 9054, New Zealand.|Center of Ecology, Evolution and Biochemistry, Department of Fish Ecology and Evolution, EAWAG Swiss Federal Institute of Aquatic Science and Technology, Seestrasse 79, 6047, Kastanienbaum, Switzerland.
authors.forename: Katharina
authors.initials: K
authors.lastname: Lange
mesh_terms: D000383:Agriculture / Q000379:methods; D000818:Animals; D000829:Animals, Domestic / Q000382:microbiology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017920:Antiporters / Q000235:genetics; D001419:Bacteria / Q000187:drug effects* / Q000235:genetics*; D018441:Biofilms / Q000254:growth & development*; D016208:Databases, Factual; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005618:Fresh Water / Q000382:microbiology*; D005798:Genes, Bacterial / Q000235:genetics; D006801:Humans; D020071:Interspersed Repetitive Sequences / Q000235:genetics; D008780:Methyltransferases / Q000235:genetics; D008826:Microbial Sensitivity Tests; D009520:New Zealand; D013753:Tetracycline Resistance / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D017920:Antiporters; D008780:Methyltransferases; C035181:rRNA (adenosine-O-2'-)methyltransferase
keywords: Antibiotic resistance genes; Freshwater; Land use; Total nitrogen