Removal of tetracycline-resistant Escherichia coli and its genes through ultrasound treatment combined with ultraviolet light emitting diodes

Abstract

Antibiotic resistance has gained increasing attention worldwide, and wastewater treatment plants have been regarded as hotspots for antibiotic-resistant bacteria and antibiotic-resistant genes (ARGs). In this study, we evaluated the removal of tetracycline-resistant Escherichia coli and its related genes through ultrasound (US) treatment with different input levels of US-specific energy combined with ultraviolet light emitting diodes (UV-LEDs). Simultaneous US with UV-LEDs effectively eliminated tetracycline-resistant E. coli with the normal suggested UV-LEDs dosage (below 30 mJ/cm2). The removal efficiency increased with the addition of US (specific input energy of 8–16 kJ/L), and simultaneous US treatment with UV-LEDs was relatively more effective than US pretreatment. Analyses of cell damage by K+ leakage and flow cytometry showed that the cell wall kept its integrity during the applied treatment conditions. Consequently, the removal efficiencies of 16 S rRNA, tet M, and tet Q were unsatisfactory because less than 1 log reduction was achieved. Increasing the US energy remarkably damaged the cell wall and potentially promoted the reaction. The removal of ARGs increased four times when using US-specific input energy at 330 kJ/L with 5 mJ/cm2 compared with UV-LEDs alone. The US treatment combined with UV-LEDs is a novel process that does not require chemicals. Results of this research can provide theoretical support for the removal of ARGs.