Dissolved oxygen facilitates efficiency of chlorine disinfection for antibiotic resistance.

Controlling the dissemination of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) is a global concern. While commonly used chlorine disinfectants can damage or even kill ARB, dissolved oxygen (DO) may affect the formation of reactive chlorine species. This leads to the hypothesis that DO may play roles in mediating the effectiveness of chlorine disinfection for antibiotic resistance. To this end, this study investigated the impacts of DO on the efficiency of chlorine disinfection for antibiotic resistance. The results revealed that DO could increase the inactivation efficiency of ARB under chloramine and free chlorine exposure at practically relevant concentrations. Reactive species induced by DO, including H ₂ O ₂ , O ₂ ^- , and OH, inactivated ARB strains by triggering oxidative stress response and cell membrane damage. In addition, the removal efficiency of extracellular ARGs (i.e. tetA and bla _TEM ) was enhanced with increasing dosage of free chlorine or chloramine under aerobic conditions. DO facilitated the fragmentation of plasmids, contributing to the degradation of extracellular ARGs under exposure to chlorine disinfectants. The findings suggested that DO facilitates disinfection efficiency for antibiotic resistance in water treatment systems.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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