Evaluation of antibiotic resistance in a full-scale algerian wastewater treatment plant: environmental protection implications

Urban wastewater treatment plants are considered to be major reservoirs of antibiotic-resistant bacteria and antibiotic resistance genes. In this study, the effectiveness of biological treatment at the East station in the town of Tizi-Ouzou, Algeria, was assessed highlighting the importance of preserving the environment, including aquatic ecosystems. The analyses covered a range of parameters: physico-chemical (SM, BOD₅, COD, NO₃⁻, NO₂⁻, NH4⁺, PO₄⁻³-, conductivity, pH and temperature), measured in the laboratory using standardised methods, the abundance of 3 bacterial groups (heterotrophs, enterobacteria and enterococci) and their resistance to 6 antibiotics were assessed using the membrane filtration technique. The abundance and prevalence of the 16SrRNA, uidA and marA genes, 9 antibiotic resistance genes and the class 1 integrase gene determined by qPCR. The results of the physico-chemical analyses indicated that the examined parameters were compliant. Beta-lactam resistant bacteria were more abundant than those resistant to vancomycin, ciprofloxacin or gentamicin. In general, antibiotic resistant bacteria abundance reduced with treatment, except the fraction of imipenem resistant total heterotrophs that increased. The class 1 integrase gene and all the antibiotic resistant genes targeted were detected in the wastewater samples. Most decreased after treatment, with the exceptions of the genes bla_IMP and bla_KPC, associated with carbapenem resistance that increased. These results corroborate earlier studies showing that conventional wastewater treatment has a limited capacity to control nutrient loading and eliminate antibiotic-resistant bacteria and genes, which could have serious consequences for the receiving environment.