| The widespread use of antibiotics to treat humans and livestock has increased the risk of contamination of water environments by bacteria with resistance to antibiotics. This study is to clarify actual conditions of antibiotic resistant bacteria in water environments by investigating the concentration of antibiotic resistant bacteria in treated wastewater. The effect of inactivation by chlorination of antibiotic resistant E. coli was also examined, and the antibiotic resistance genes in samples of each of these E. coli strains were analyzed. The results revealed many E. coli strains with antibiotic resistance to ampicillin in wastewater from wastewater treatment plants and river water. A high percentage of ampicillin resistant E. coli in rivers and wastewater have multi-drug resistance. However, the detected level of the antibiotic resistant E. coli was low in river waters not polluted by humans and livestock. The resistance of multi-drug resistant E. coli which was added to treated wastewater did not show any change. Multi-drug resistant E. coli required a 1.1- to 1.4-fold higher Ct value for 3-log inactivation by chlorination than E. coli without resistance to antibiotics. It was confirmed that these E. coli strains had the antibiotic resistance gene. |
