Exploring the links between antibiotic occurrence, antibiotic resistance, and bacterial communities in water supply reservoirs

Antibiotic resistance represents a growing global health concern due to the overuse and misuse of antibiotics. There is, however, little information about how the selective pressure of clinical antibiotic usage can affect environmental communities in aquatic ecosystems and which bacterial groups might be responsible for dissemination of antibiotic resistance genes (ARGs) into the environment. In this study, chemical and biological characterization of water and sediments from three water supply reservoirs subjected to a wide pollution gradient allowed to draw an accurate picture of the concentration of antibiotics and prevalence of ARGs, in order to evaluate the potential role of ARGs in shaping bacterial communities, and to identify the bacterial groups most probably carrying and disseminating ARGs. Results showed significant correlation between the presence of ARG conferring resistance to macrolides and the composition of bacterial communities, suggesting that antibiotic pollution and the spreading of ARG might play a role in the conformation of bacterial communities in reservoirs. Results also pointed out the bacterial groups Actinobacteria and Firmicutes as the ones probably carrying and disseminating ARGs. The potential effect of antibiotic pollution and the presence of ARGs on the composition of bacterial communities in lacustrine ecosystems prompt the fundamental question about potential effects on bacterial-related ecosystem services supplied by lakes and reservoirs. © 2013 Elsevier B.V.We thank Carles Borrego, Enrique Navarro, and Veronica Ribé for helpful discussions and comments to the article, and Jaime Ordóñez for help during field work. We also thank George A. Jacoby, Carmen Torres and Joan Jofre for providing us with bacterial strains. This research work was funded by the 1st Interdisciplinary Water Research Projects-ICRA Grants Program 2010 (Project RES2), the Spanish Ministry of Economy and Competitiveness for its financial support through the project SCARCE (Consolider-Ingenio 2010 CSD2009-00065), and by the European Union through the European Regional Development Fund (FEDER). This work was also partly supported by the Generalitat de Catalunya (Consolidated Research Group: Water and Soil Quality Unit 2009-SGR-965). Prof. Barceló acknowledges King Saud University for his visiting professorship.Peer Reviewe