The effect of tetracycline in the antibiotic resistance gene transfer before and after ozone disinfection

Antibiotics are currently considered to be an emerging threat to the aquatic environment if left untreated. Persistence of antibiotic compounds has been detected in vast aquatic environments, including wastewater. This involves the development and increase of antibiotic resistance and bacterial presence in the aquatic communities. Several previous studies have been conducted for the removal of micro-contaminants by ozonation. The comprehensive study on residual antibiotics effect to antibiotic resistance transfer before and after oxidation has not yet been explored. Accordingly, the aim of this study is to (1) investigate the antibiotic resistance growth under the presence of tetracycline in short and long period without oxidation process and to (2) look into the amount of residual tetracycline that persists after oxidation and its possible effect in potentially influencing antibiotic resistance gene (ARG) transfer among bacteria. As shown in the results, a few ppm or few hundred ppb of tetracycline, regardless of ozonation, enhanced the ARG transfer compared to control. These results implied that ARG transfer can be enhanced by incomplete removal of micro-contaminants in the environment.