Effects of ultraviolet disinfection on antibiotic-resistant Escherichia coli from wastewater: inactivation, antibiotic resistance profiles and antibiotic resistance genes.

Abstract

To evaluate the effect of ultraviolet (UV) disinfection on antibiotic-resistant Escherichia coli. Antibiotic-resistant E.coli strains were isolated from a wastewater treatment plant and subjected to UV disinfection. The effect of UV disinfection on the antibiotic resistance profiles and the antibiotic resistance genes (ARGs) of antibiotic-resistant E.coli was evaluated by a combination of antibiotic susceptibility analysis and molecular methods. Results indicated that multiple-antibiotic-resistant (MAR) E.coli were more resistant at low UV doses and required a higher UV dose (20mJcm-2 ) to enter the tailing phase compared with those of antibiotic-sensitive E.coli (8mJcm-2 ). UV disinfection caused a selective change in the inhibition zone diameters of surviving antibiotic-resistant E.coli and a slight damage to ARGs. The inhibition zone diameters of the strains resistant to antibiotics were more difficult to alter than those susceptible to antibiotics because of the existence and persistence of corresponding ARGs. The resistance of MAR bacteria to UV disinfection at low UV doses and the changes in inhibition zone diameters could potentially contribute to the selection of antibiotic-resistant bacteria in wastewater treatment after UV disinfection. The risk of spread of antibiotic resistance still exists owing to the persistence of ARGs. Our study highlights the acquisition of other methods to control the spread of ARGs.