In vitro activity of sulbactam in combination with other antimicrobial agents against extensively drug-resistant Acinetobacter baumannii

Abstract

This study evaluated the in vitro effectiveness of SUL combined with other antibiotics against XDR Acinetobacter baumannii . Sixty-two clinical isolates were tested using broth microdilution and checkerboard methods. The SUL MIC 50 was 64 mg/L, with tigecycline and colistin showing lower MIC ranges and higher fosfomycin. Synergistic activity was most notable with SUL/fosfomycin (41.9%), followed by SUL/amikacin (19.3%) and SUL/meropenem (17.7%). Antagonism was rare (1.6%–3.2%). Time–kill assays showed that the four-drug combination of SUL/fosfomycin/amikacin/meropenem had sustained bactericidal activity over 24 hours. While SUL-based combinations showed variable synergy, further studies are needed to determine their clinical potential.