Inactivation of vancomycin-resistant Enterococcus faecalis and degradation of intracellular vanB gene under exposure to UV and UV/H2O2

Abstract

The proliferation of antibiotic resistance in water environment which may cause antibiotic therapy failure has attracted worldwide attention. However, the effects of UV-based advanced oxidation processes on inactivation of antibiotic resistant bacteria (ARB) and degradation of antibiotic resistance genes (ARGs) have not been well studied. This study aimed to comparatively investigate the removal efficacy in inactivating the vancomycin-resistant Enterococcus faecalis (VRE) and degrading its containing vanB gene under exposure to UV and UV/H2O2. The results showed that VRE was readily inactivated in both UV and UV/H2O2 processes. Although UV/H2O2 was only slightly superior to UV alone in VRE inactivation, it significantly inhibited the bacterial photoactivation and regrowth. UV/H2O2 indeed achieved synergistic degradation of intracellular vanB (0.1–0.8 log), which could be further enhanced by increasing the UV intensity, lowering pH and adding H2O2 in batches. The enhanced induction of OH resulted in the cell membrane damage, facilitating the entrance of excess OH and more efficiently oxidizing the released intracellular ARGs. Overall, the presence of humic acid inhibited the inactivation of VRE and degradation of vanB, while lower concentrations of humic acid (2.5–5 mg/L) could act as free radical initiator and slightly promoted vanB degradation in UV/H2O2 process. Our findings suggested that UV/H2O2 has more advantages on the control of ARB and intracellular ARGs compared to UV alone.