Abundance of antibiotic resistance genes and removal of antibiotic resistant E. coli in to Norwegian wastewater treatment plants

Summary

The effectivity of different treatment stages at two wastewater treatment plants (WWTPs) to remove cultivable antibiotic resistant E. coli from municipal wastewater from Oslo City was investigated. The WWTPs were effective in reducing total cultivable E. coli, however, full hygienization was not achieved. The E. coli in WWTP samples were partly resistant to ampicillin and co-trimoxazole, and to a lesser extent, tetracycline and ciprofloxacin. The plants showed different patterns with respect to the removal of resistant E. coli. Analysis of selected antibiotics maker genes in samples from WWTP effluent revealed the presence of resistance against commonly used groups of antibiotics, but also to such that are rarely used and belong to critically important antibiotics, including carbapenemes, colistin and cefalosporines. By membrane filtration of WWTP effluents, using lab-scale ultra- and nanofiltration, all cultivable E. coli, including antibiotic resistant ones, were removed completely.