title: Antibiotic resistance of enterococci and related bacteria in an urban wastewater treatment plant.
abstract: The main objective of this work was to study the ecology of enterococci and related bacteria in raw and treated wastewater from a treatment plant receiving domestic and pretreated industrial effluents in order to assess the influence of treatment on the prevalence of antibiotic resistance phenotypes among this group of bacteria. The predominant species found in the raw wastewater were Entercoccus hirae, Entercoccus faecium and Entercoccus faecalis. Wastewater treatment led to a reduction in E. hirae (alpha<0.1) and an increase in E. faecium (alpha<0.1); the relative proportions of E. faecalis remained the same in the raw and in the treated wastewater. Among the isolates tested, no vancomycin resistance was observed among the enterococci. Entercoccus faecium and E. faecalis showed resistance prevalence values reaching 33%, 40% and 57% for the antibiotics ciprofloxacin, erythromycin and tetracycline, respectively. Antibiotic-resistant strains of enterococci were not eliminated by wastewater treatment. A positive selection of ciprofloxacin-resistant enterococci was indicated by a significant increase in resistance prevalence (alpha<0.02) in treated wastewater compared with the raw wastewater.
authors.affiliation: Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Porto, Portugal.
authors.forename: Miguel
authors.initials: M
authors.lastname: Ferreira da Silva
authors.forename: Igor
authors.initials: I
authors.lastname: Tiago
authors.forename: António
authors.initials: A
authors.lastname: Veríssimo
authors.forename: Rui A R
authors.initials: RA
authors.lastname: Boaventura
authors.forename: Olga C
authors.initials: OC
authors.lastname: Nunes
authors.forename: Célia M
authors.initials: CM
authors.lastname: Manaia
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015373:Bacterial Typing Techniques; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial; D004463:Ecology; D016983:Enterococcus / Q000187:drug effects* / Q000302:isolation & purification*; D007220:Industrial Waste; D008826:Microbial Sensitivity Tests; D019105:Random Amplified Polymorphic DNA Technique; D012722:Sewage; D020713:Vancomycin Resistance; D014865:Waste Disposal, Fluid; D014871:Water Microbiology
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D007220:Industrial Waste; D012722:Sewage