title: Wastewater treatment plants release large amounts of extended-spectrum β-lactamase-producing Escherichia coli into the environment.
abstract: BACKGROUND
  The determinants of the spread of extended-spectrum β-lactamase-producing Escherichia coli (ESBLEC) in the community remain unclear. To evaluate its dissemination in the environment, we analyzed the ESBLEC population throughout an urban wastewater network.
  
  
  METHODS
  Samples were collected weekly, over a 10-week period, from 11 sites throughout the wastewater network of Besançon city (France). Total E. coli and ESBLEC loads were determined for each sample. As a control, we analyzed 51 clinical ESBLEC isolates collected at our hospital. We genotyped both environmental and clinical ESBLEC by pulsed-field gel electrophoresis and multilocus sequence typing and identified their blaESBL genes by sequencing.
  
  
  RESULTS
  The E. coli load was higher in urban wastewater than in hospital wastewater (7.5 × 10(5) vs 3.5 × 10(5) CFU/mL, respectively). ESBLEC was recovered from almost all the environmental samples and accounted for 0.3% of total E. coli in the untreated water upstream from the wastewater treatment plant (WWTP). The ESBLEC load was higher in hospital wastewater than in community wastewater (27 × 10(3) vs 0.8 × 10(3) CFU/mL, respectively). Treatment by the WWTP eliminated 98% and 94% of total E. coli and ESBLEC, respectively. The genotyping revealed considerable diversity within both environmental and clinical ESBLEC and the overrepresentation of some clonal complexes. Most of the sequence types displayed by the clinical isolates were also found in the environment. CTX-M enzymes were the most common enzymes whatever the origin of the isolates.
  
  
  CONCLUSIONS
  The treatment at the WWTP led to the relative enrichment of ESBLEC. We estimated that >600 billion of ESBLEC are released into the river Doubs daily and the sludge produced by the WWTP, used as fertilizer, contains 2.6 × 10(5) ESBLEC per gram.
authors.affiliation: Service d'Hygiène Hospitalière, UMR 6249 Chrono-environnement, Centre Hospitalier Régional Universitaire, Université de Franche-Comté, Besançon.
authors.forename: Caroline
authors.initials: C
authors.lastname: Bréchet
authors.affiliation: Service d'Hygiène Hospitalière, UMR 6249 Chrono-environnement, Centre Hospitalier Régional Universitaire, Université de Franche-Comté, Besançon.
authors.forename: Julie
authors.initials: J
authors.lastname: Plantin
authors.affiliation: Service d'Hygiène Hospitalière, UMR 6249 Chrono-environnement, Centre Hospitalier Régional Universitaire, Université de Franche-Comté, Besançon.
authors.forename: Marlène
authors.initials: M
authors.lastname: Sauget
authors.affiliation: Service d'Hygiène Hospitalière, UMR 6249 Chrono-environnement, Centre Hospitalier Régional Universitaire, Université de Franche-Comté, Besançon.
authors.forename: Michelle
authors.initials: M
authors.lastname: Thouverez
authors.affiliation: Service d'Hygiène Hospitalière, UMR 6249 Chrono-environnement, Centre Hospitalier Régional Universitaire, Université de Franche-Comté, Besançon.
authors.forename: Daniel
authors.initials: D
authors.lastname: Talon
authors.affiliation: Service d'Hygiène Hospitalière, UMR 6249 Chrono-environnement, Centre Hospitalier Régional Universitaire, Université de Franche-Comté, Besançon.
authors.forename: Pascal
authors.initials: P
authors.lastname: Cholley
authors.affiliation: Département DISC, Institut FEMTO-ST, UMR 6174 CNRS, Université de Franche-Comté, Belfort, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Guyeux
authors.affiliation: Service d'Hygiène Hospitalière, UMR 6249 Chrono-environnement, Centre Hospitalier Régional Universitaire, Université de Franche-Comté, Besançon.
authors.forename: Didier
authors.initials: D
authors.lastname: Hocquet
authors.affiliation: Service d'Hygiène Hospitalière, UMR 6249 Chrono-environnement, Centre Hospitalier Régional Universitaire, Université de Franche-Comté, Besançon.
authors.forename: Xavier
authors.initials: X
authors.lastname: Bertrand
mesh_terms: D002947:Cities; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D005602:France; D005838:Genotype; D006761:Hospitals; D008826:Microbial Sensitivity Tests; D010802:Phylogeny; D045483:Rivers / Q000382:microbiology; D012722:Sewage / Q000382:microbiology*; D014871:Water Microbiology; D014873:Water Pollutants / Q000032:analysis*; D014876:Water Pollution / Q000032:analysis*; D018508:Water Purification; D001618:beta-Lactamases / Q000378:metabolism*
chemical_list: D012722:Sewage; D014873:Water Pollutants; D001618:beta-Lactamases
keywords: WWTP; environmental risk; multidrug-resistant bacteria; sequence types; sludge