title: Characterization of ciprofloxacin-resistant isolates from a wastewater treatment plant and its receiving river.
abstract: In this study we characterised the ciprofloxacin-resistant strains isolated in biofilm and sediments from a wastewater treatment plant (WWTP) discharge point and its receiving river. We also examined the prevalence of qnrA, qnrB, qnrS and aac(6')-Ib-cr genes in these isolates and determined whether they harbour plasmid-encoded β-lactamases such as TEM, SHV and CTX-M. Moreover, antibiotic concentrations were also measured to evaluate the level of contamination of these pharmaceuticals in the sampling area. Antibiotics were found in the range of ng L(-1) in WWTP effluents, but most of them were no longer found in downstream river. However, some fluoroquinolones were detected in sediment downstream demonstrating their high persistence and their capacity to be retained in the river sediments. Most of the ciprofloxacin-resistant isolates belonged to the Gammaproteobacteria class and 17 of them, 8 (7.6%) from the first sampling and 9 (6.1%) from the second sampling, carried a qnr gene. In particular, 15 isolates carried the qnrS gene and 2 carried the qnrB gene. Among the qnr-positive isolates, 12 harboured the aac(6')-lb-cr gene and 2 of them also carried a β-lactamase on the same plasmid, indicating that they may be transferred simultaneously. It is also noteworthy that all qnr-positive isolates identified as Aeromonas species harboured the same qnrS allele, namely the qnrS2. This study reinforces the importance of environmental bacteria as vehicles for dissemination of antibiotic resistance genes.
authors.affiliation: Catalan Institute for Water Research (ICRA), Scientific and Technological Park of the University of Girona, Emili Grahit 101, 17003 Girona, Spain. Electronic address: emarti@icra.cat.
authors.forename: Elisabet
authors.initials: E
authors.lastname: Marti
authors.affiliation: Catalan Institute for Water Research (ICRA), Scientific and Technological Park of the University of Girona, Emili Grahit 101, 17003 Girona, Spain.
authors.forename: Belinda
authors.initials: B
authors.lastname: Huerta
authors.affiliation: Catalan Institute for Water Research (ICRA), Scientific and Technological Park of the University of Girona, Emili Grahit 101, 17003 Girona, Spain.
authors.forename: Sara
authors.initials: S
authors.lastname: Rodríguez-Mozaz
authors.affiliation: Catalan Institute for Water Research (ICRA), Scientific and Technological Park of the University of Girona, Emili Grahit 101, 17003 Girona, Spain; Water and Soil Quality Research Group, Department of Environmental Chemistry, IDAEA-CSIC, Jordi Girona 18-26, 08034 Barcelona, Spain.
authors.forename: Damià
authors.initials: D
authors.lastname: Barceló
authors.affiliation: Department of Microbiology, Faculty of Biology, University of Barcelona, Av. Diagonal 643, 08028 Barcelona, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Jofre
authors.affiliation: Catalan Institute for Water Research (ICRA), Scientific and Technological Park of the University of Girona, Emili Grahit 101, 17003 Girona, Spain.
authors.forename: José Luis
authors.initials: JL
authors.lastname: Balcázar
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification*; D002939:Ciprofloxacin / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D060885:Multiplex Polymerase Chain Reaction; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013030:Spain; D062065:Wastewater / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D002939:Ciprofloxacin; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; D062065:Wastewater
keywords: Antibiotic resistance; Antibiotics; Biofilm; Sediment; Wastewater treatment plant; qnr genes