Antibiotic resistance of enterococci and related bacteria in an urban wastewater treatment plant

The main objective oflhis work was to study the ecology of enterooocci 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 ofbacteria. The predominant species found in the raw wastewater-were Erztercaccus hirae, Entercoc- cus faecium and Enrercnrcus faecalis. Wastewater treatment led to a reduction in E. hirae (ar < 0.1) and an increase Ln B fnecium [nt < [}_1); the relative proportions ofE. fczecalis remained the same in the raw and in the treated wastewater. Among the isolates tested, no vanoornyclln resistance was observed among the cnterococci. Entercoccus faecium and E. fneculis showed resistance prevalence values reaching 33%. 40% and 57% for the antibiotics ciprofloxacin, erythromycin and tetracycline, respectively. Antibiotieresistant 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 (ac < 0.52) in treated wastewater compared with the raw wastewater.