Abstract: OBJECTIVE To explore the in vitro and in vivo antibacterial effects of paromomycin sulfate combined with meropenem on carbapenem-resistant Klebsiella pneumoniae (CRKP) so as to provide experimental evidence for clinical combined treatment of CRKP infections. METHODS Totally 6 strains of representative CRKP that produced OXA-48, NDM, KPC, IMP and VIM were enrolled in the study. The minimum inhibitory concentrations (MICs) of paromomycin sulfate and meropenem were determined by the microdilution method. The fractional inhibitory concentration index (FICI) was calculated by the checkerboard dilution method so as to evaluate the synergistic effect of the combination of the two drugs (FICI≤0.5 considered as the synergistic effect). The antibacterial activity and sterilization rate of the combination within 24 hours were dynamically monitored by time-killing dynamic experiment. A Galleria mellonella infection model was established to observe the effects of the combination on the survival rate and histopathological changes of the larvae with CRKP infection. RESULTS The FICI of paromomycin sulfate combined with meropenem against 6 strains of CRKP producing different types of enzymes ranged from 0.258 to 0.375, showing synergistic effects (100.00%). The result of time-killing dynamic experiment indicated that the antibacterial effect of the combination was better than that of the single drug(all P＜0.001). In vivo, the combination treatment group exhibited a markedly increased survival rate of G. mellonella and a notable reduction of melanized foci (reflecting bacterial burden) in tissue sections, indicating that this combination could effectively reduced the in vivo bacterial load. CONCLUSION The combination of paromomycin sulfate and meropenem demonstrates excellent synergistic inhibitory effects on various carbapenemase-producing CRKP both in vitro and in vivo, providing a new potential combination strategy for the clinical treatment of CRKP-induced severe infections.