title: Antibiotic-resistant Escherichia coli in karstic systems: a biological indicator of the origin of fecal contamination?
abstract: Occurrences of antibiotic-resistant Escherichia coli in two springs of a karstic system (NW France) providing drinking water were determined to study the role of aquifers in the dissemination of the resistance genes. Water samples were collected during wet and dry periods and after a heavy rainfall event to investigate E. coli density, antibiotic resistance patterns, and occurrences of class 1, 2, and 3 integrons. By observing patterns of the resistant isolates (i.e. number and type of resistances) and their occurrences, we were able to define two resistant subpopulations, introduced in the aquifer via surface water: (1) R1-2, characterized by one or two resistance(s), essentially to chloramphenicol and/or tetracycline (96.5%), was always found during the heavy rainfall event; (2) R3-10, characterized by three or more resistances, mostly resistant to tetracycline (94.1%) and beta-lactams (86%), was found transiently. Class 1 and 2 integrons were detected, mostly in the R3-10 subpopulation for class 1 integrons. The characteristics of these two subpopulations strongly suggest that the contamination originates from pasture runoff for the R1-2 subpopulation and from wastewater treatment plant effluents for the R3-10 subpopulation. These two subpopulations of E. coli could be used as biological indicators to determine the origin of groundwater contamination.
authors.affiliation: UMR CNRS 6143, Morphodynamique Continentale et Côtière, M2C, Mont Saint Aignan, France. angela.floresribeiro@etu.univ-rouen.fr
authors.forename: Angela Flores
authors.initials: AF
authors.lastname: Ribeiro
authors.forename: Emilie
authors.initials: E
authors.lastname: Laroche
authors.forename: Guillaume
authors.initials: G
authors.lastname: Hanin
authors.forename: Matthieu
authors.initials: M
authors.lastname: Fournier
authors.forename: Laurent
authors.initials: L
authors.lastname: Quillet
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Dupont
authors.forename: Barbara
authors.initials: B
authors.lastname: Pawlak
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D024881:Drug Resistance, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D005243:Feces / Q000382:microbiology; D005602:France; D060587:Groundwater / Q000382:microbiology*; D032023:Integrons; D013752:Tetracycline / Q000494:pharmacology; D062065:Wastewater / Q000382:microbiology*; D047090:beta-Lactams / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D013752:Tetracycline; D062065:Wastewater; D047090:beta-Lactams