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The excessive dissemination of New Delhi metallo-β-lactamase-1 (NDM-1), which mediates resistance to a majority of clinical β-lactam antibiotics, has created a major public health problem worldwide. Herein, a bla NDM-1 -carrying (plasmid encoded) super-resistant bacterium, Acinetobacter sp. CS-2, was selected to reveal its mechanisms of inactivation and photoreactivation during UV, chlorination and UV/chlorination disinfection. The inactivated CS-2 underwent a certain photoreactivation after UV and chlorination. The logistic model precisely fitted the data obtained in the photoreactivation experiments by UV treatment, with the estimated kinetic parameters S m (0.530%−12.071%) and k 2 (0.0009–0.0471). The photoreactivation of Acinetobacter sp. CS-2 was observed when treated by chlorination at a dosage of 0.5 mg/L with a survival ratio of 34.04%. UV/chlorination not only resulted in the high-efficiency reduction of CS-2 but also effectively controlled its photoreactivation with a survival ratio of 0%− 0.87%. UV/chlorination showed great advantages in causing the irreversible destruction of bacterial surface structures by making the cell membranes wrinkled and incomplete compared with UV disinfection. The singlet oxygen (1O 2) generated during UV/chlorination treatment played a vital role in bla NDM-1 removal. This study proposed new insights into the mechanism of inactivation and the characteristics of photoreactivation for the super-resistant bacteria by UV, chlorination and UV/chlorination. [Display omitted] • Logistic model precisely fitted photoreactivation experiments of superbug. • Photoreactivation and decay period were observed when treated by chlorination. • Irreversible destruction of cell surface structures by UV/chlorination treatment. • Singlet oxygen plays an important role on the plasmid-encoded bla NDM-1 removal. [ABSTRACT FROM AUTHOR]

[Display omitted] • UV/PMS could efficiently inactivate ARB and control the risk of photoreactivation. • bla NDM-1 was greater resistance to UV/PMS than bla OXA-58 in the same plasmid. • ARGs base pairs number and length were responsible for ARGs removal. • 1O 2 plays an important role on the plasmid-encoded ARGs removal in UV/PMS. The super-resistant bacteria that produce the New Delhi metallo-β-lactamase 1 (NDM-1) enzyme are becoming a conceivably major worldwide clinical issue with serious consequences. Studying the disinfection and mechanism of super-resistant bacteria and their antibiotic resistance genes (ARGs) is crucial for controlling their spread in the water environment. In this study, the disinfection of the super-resistant bacterium Acinetobacter sp. CS-2 and its transferable ARGs (plasmid-encoded bla NDM-1 and bla OXA-58) by ultraviolet radiation (UV), peroxymonosulfate (PMS), and ultraviolet/peroxymonosulfate (UV/PMS) exposure were investigated. UV/PMS could completely inactivate CS-2 and control the photoreactivation risk, while bacteria that underwent UV and PMS treatment had survival ratios of 0.22% and 0.28%, respectively. The removal efficiencies of bla NDM-1 and bla OXA-58 ranged from 3.64 to 4.05 log, and the advantage of UV/PMS treatment on ARGs damage was further identified by gel electrophoresis analysis. The removal efficiency of bla NDM-1 was lower than that of bla OXA-58 , which was attributed to the low number of adjacent 5′-TT-3′ harbored by bla NDM-1. The removal rate constants of the ARGs by UV treatment were significantly correlated with the number of adjacent base pairs (e.g., 5′-TT-3′, 5′-CT-3′, 5′-TC-3′ and 5′-CC-3′) and length, with R -values ranging from 0.9044 to 0.9512. Singlet oxygen (1O 2) played a vital role in the reduction of bla NDM-1 and bla OXA-58 in the UV/PMS treatment. UV/PMS showed high removal efficiency under natural pH conditions and in the presence of various aqueous ions (e.g., Cl−, SO 4 2− and HCO 3 −). Overall, this study provides new understandings and theoretical support for the risk control of super-resistant bacteria and plasmid-encoded ARGs. [ABSTRACT FROM AUTHOR]