Restoration of Susceptibility of bla _NDM -bearing Escherichia. coli to Carbapenem Antibiotics by Exogenous N -acetylcysteine

The global spread of the New Delhi metallo-β-lactamase (NDM) -producing carbapenem-resistant Enterobacteriaceae pose a serious threat to public health, as NDM and its variants enzymes efficiently hydrolyze almost β-lactam antibiotics. The development of novel antibiotics or antibiotic adjuvants capable of eradicating antibiotic-resistance bacteria through multiple mechanisms represents a promising strategy for reversing antibiotic resistance and preventing the emergence of new resistance. In this study, we utilized high-performance liquid chromatography (HPLC) to demonstrate that N -acetylcysteine (NAC) is a prominent reducing metabolite in bacteria harboring NDM-5. Notably, NAC was able to restore carbapenem susceptibility in NDM-producing bacteria in vitro. Subsequently, we further investigated the underlying mechanisms involved. Our findings revealed that NAC exerts its effect through multiple mechanisms that collectively contribute to reversing meropenem resistance. Firstly, NAC may inhibit biofilm formation and reduces polysaccharide production in NDM-positive Escherichia coli . and this potential mechanism was verified by transcriptomic analysis, reverse transcription PCR (RT-PCR) and a biofilm restoration experiment involving the addition of citrate cycle intermediate metabolites. Secondly, RT-PCR analysis demonstrated that NAC significantly downregulates the expression of bla _NDM-5 . Additionally, NAC exhibited competitive inhibition of NDM activity in vitro. Thirdly, NAC was found to enhance the intracellular accumulation of meropenem, therapy increasing its bactericidal efficacy. These three independent mechanisms offer valuable insights for developing adjuvants. The discovery offers a promising prospect for combating the antibiotic resistance concern. This study paves the way for further exploration and potential clinical applications in the fight against antibiotic-resistant bacterial infections.