Abstract：Objective: To evaluate the antibacterial activity of amtraxam (ATM) combined with Ceftazidime/avibactam (CZA) against carbapenem resistant enterobacter cloacae complex group in vitro, and to analyze the production and genotype distribution of carbapenase in CRECC. Methods: A total of 46 CRECC strains were collected from 2021 to 2023. The combined antibacterial effect of ATM and CZA was evaluated by microbroth dilution checkerboard method, and the type of action was determined according to fractional inhibitory concentration (FIC). The modified carbapenem inactivation method (mCIM) and EDTA modified carbapenem inactivation method (eCIM) were used to confirm whether the strain produced carbapenase and preliminatively distinguish class A and Class B carbapenase, and the carbapenase genotypes were further confirmed by immunochromatography. Results: In 46 strains of CRECC, ATM combined with CZA showed synergistic effect (FIC≤0.5) in 39 strains, additive effect (0.5<FIC≤1) in 7 strains, no unrelated or antagonistic effect was found. The minimum inhibitory concentration (MIC) of ATM decreased significantly from 256 mg/L to 0.008 mg/L, which was reduced by 32,000 times. The MIC of CZA was reduced from 64 mg/L to 0.015 mg/L, a 4,267-fold decrease. Carbapenase genotype analysis confirmed that 38 of 46 CRECC strains produced carbapenase NDM (82.61%), and 8 strains did not produce carbapenase (17.39%). The combination of ATM and CZA showed synergistic effect (31 strains, 81.58%) or additive effect (7 strains, 18.42%) in 38 enzyme-producing strains, and synergistic effect in 8 strains without enzyme-producing CRECC strains. Conclusion: The popular CRECC in this region mainly produces NDM carbapenemase. ATM combined with CZA showed significant antibacterial activity against CRECC in vitro. The combination regimen has shown promising potential in combating CRECC and is expected to be an effective regimen for the treatment of such infections. In the future, it is necessary to further study the clinical application effect and safety to optimize the treatment strategy.
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2026, Vol. 32 
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