Review Urban wastewater treatment plants as hotspots for antibiotic resistant bacteria and genes spread into the environment: A review L. Rizzo a, ⁎, C. Manaia b , C. Merlin c , T. Schwartz d , C. Dagot e , M.C. Ploy f , I. Michael g , D. Fatta-Kassinos g a Department of Civil Engineering, University of Salerno, 84084, Fisciano (SA), Italy b CBQF/Escola Superior de Biotecnologia, Universidade Católica Portuguesa, R. Dr. António Bernardino de Almeida, 4200-072, Porto, Portugal c Laboratoire de Chimie Physique et Microbiologie pour l'Environnement (LCPME), UMR 7564 CNRS-Université de Lorraine, 15 Avenue du Charmois, 54500 Vandoeuvre-les-Nancy, France d Department of Microbiology at Interfaces, Karlsruhe Institute of Technology (KIT) – Northern Campus, Institute of Functional Interfaces (IFG), D-76344 Eggenstein-Leopoldshafen, Germany e Université of Limoges, EA4330, GRESE, ENSIL, F87000, Limoges, France f Université de Limoges, INSERM, UMR S1092, F-87000, Limoges, France g Nireas, International Water Research Centre, University of Cyprus, 1 Panepistimiou Avenue, P.O Box 20537, 1678 Nicosia, Cyprus HIGHLIGHTS ► UWTPs may positively affect ARB spread and selection as well as ARG transfer. ► Resistance integrons may be used to characterize ARG transfer. ► High trough technologies are a useful complementation of PCR technologies. ► Biological process effect on ARB and ARG transfer should be further investigated. ► Advanced treatments/disinfection ef- fect should be further investigated too. GRAPHICAL ABSTRACT abstract article info Article history: Received 23 November 2012 Received in revised form 8 January 2013 Accepted 8 January 2013 Available online 7 February 2013 Keywords: Antibiotic resistant bacteria Antibiotic resistance genes Antibiotic resistance dissemination Advanced wastewater treatment Biological process Disinfection Urban wastewater treatment plants (UWTPs) are among the main sources of antibiotics' release into the environ- ment. The occurrence of antibiotics may promote the selection of antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB), which shade health risks to humans and animals. In this paper the fate of ARB and ARGs in UWTPs, focusing on different processes/technologies (i.e., biological processes, advanced treatment technologies and disinfection), was critically reviewed. The mechanisms by which biological processes influence the develop- ment/selection of ARB and ARGs transfer are still poorly understood. Advanced treatment technologies and disinfec- tion process are regarded as a major tool to control the spread of ARB into the environment. In spite of intense efforts made over the last years to bring solutions to control antibiotic resistance spread in the environment, there are still important gaps to fill in. In particular, it is important to: (i) improve risk assessment studies in order to allow accu- rate estimates about the maximal abundance of ARB in UWTPs effluents that would not pose risks for human and environmental health; (ii) understand the factors and mechanisms that drive antibiotic resistance maintenance and selection in wastewater habitats. The final objective is to implement wastewater treatment technologies capa- ble of assuring the production of UWTPs effluents with an acceptable level of ARB. © 2013 Elsevier B.V. All rights reserved. Science of the Total Environment 447 (2013) 345–360 ⁎ Corresponding author. Tel.: +39 089 969334; fax: +39 089 969620. E-mail address: l.rizzo@unisa.it (L. Rizzo). 0048-9697/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.scitotenv.2013.01.032 Contents lists available at SciVerse ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv