Synergistic effects of ceftriaxone combined with BLI-489 against NDM-producing Klebsiella pneumoniae

ABSTRACT The New Delhi metallo-β-lactamase-producing Klebsiella pneumoniae (NDM-Kp) strain is a high-risk pathogen responsible for many multidrug-resistant (MDR) infections worldwide, particularly in healthcare settings. The scarcity of effective metallo-β-lactamase (MBL) inhibitors highlights the urgent need for novel therapeutic strategies to combat this threat. In this study, we evaluated the synergistic effects of ceftriaxone (CRO) with the β-lactamase inhibitor BLI-489, aiming to restore the efficacy of cephalosporins against NDM- Kp strains. The CRO/BLI-489 exhibited significant synergistic activity in vitro , as indicated by a fractional inhibitory concentration index (FICI) of 0.25. The combination significantly reduced the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against NDM- Kp . This combination also inhibited biofilm formation. Hemolysis assays revealed that the hemolytic activity was significantly lower after treatment with CRO/BLI-489 compared to that recorded after treatment with each compound alone. This finding indicated that the combination treatment has higher biocompatibility and retains antimicrobial efficacy. Molecular dynamics (MD) simulations revealed that the synergistic antibacterial effect of the CRO/BLI-489 is mediated by interactions involving coordination with Zn 2+ ions in the catalytic site of the MBL enzyme. These results suggest that the combination can overcome MBL-mediated resistance mechanisms. IMPORTANCE The global spread of NDM-Kp poses a major challenge to healthcare systems because of the scarcity of effective treatment options. In response to the urgent need for new therapeutic strategies, this study explores the CRO/BLI-489 as a promising alternative for overcoming MBL-mediated resistance. Although not yet an established therapy, this approach demonstrates the potential to restore cephalosporin efficacy, inhibit biofilm formation, and reduce cytotoxicity. These results offer valuable insights that may guide the development of future treatments for infections caused by multidrug-resistant pathogens. Our findings underscore the importance of further preclinical and clinical studies to validate this strategy and contribute to the global effort against antibiotic resistance.