In vitro antimicrobial activity of sulbactam-durlobactam combined with 14 types of antibiotics against clinical Acinetobacter baumannii isolates

OBJECTIVE To evaluate the antibacterial activity of sulbactam/durlobactam combined with other common antibacterial agents against Acinetobacter baumannii through three types of in vitro combined antibacterial susceptibility tests.

METHODS A total of 84 strains of A. baumannii isolated from clinical specimens at Zhongshan Hospital Affiliated to Fudan University from Feb. to Mar. 2025 were collected. The in vitro synergistic efficacy rates of sulbactam/durlobactam combined with 14 other common antibacterial agents were detected with the double-disk synergy test, broth disk elution method and combined killing curve assay.

RESULTS The double-disk synergy test showed that the efficacy rates of sulbactam/durlobactam combined with other antibacterial agents, in a descending order, were as follows: cefoperazone/sulbactam 85.71%, ceftazidime 76.19%, cefepime 76.19% and piperacillin/tazobactam 72.62%. Quantitative results from the combined killing curve assay indicated that sulbactam/durlobactam combined with the mentioned four drugs all exhibited synergistic effects after 6-12 hours. The broth disk elution method test of sulbactam/durlobactam combined with aztreonam on 12 strains of metallo-β-lactamase-producing A. baumannii showed a combined antibacterial efficacy rate of 50.00%.

CONCLUSIONS Sulbactam/durlobactam combined with cefoperazone/sulbactam, ceftazidime, cefepime and piperacillin/tazobactam all demonstrates favorable in vitro antibacterial effects against A. baumannii. Microbiology laboratories should conduct combined antibacterial susceptibility tests, and the double-disk synergy test is recommended as a routine detection method.