Drug chemosensitivity test of etimicin combined with cefoperazone/sulbactam or piperacillin/ tazobactam against carbapenem-resistant Acinetobacter baumannii

Objective To evaluate the combined inhibitory effect of etimicin (ETM) and cefoperazone/sulbactam (SCF), etimicin (ETM) and piperacillin/tazobactam (TZP) respectively on clinically isolated carbapenem-resistant Acinetobacter baumannii (CRAB) strains in vitro. Methods This test was based on chessboard method. Individual used and combined inhibitory effect of ETM and SCF, ETM and TZP in vitro was assayed by detecting the minimum inhibitory concentration (MIC) and calculating the fractional inhibitory concentration (FIC) index in 60 CRAB strains with the micro-broth dilution method. Results Combination of ETM and SCF showed synergic effect, additive effect, indifferent effect and antagonistic effect of 8.3%, 56.7%, 35.0% and 0 on the CRAB strains respectively. Combination of ETM and TZP displayed synergic effect, additive effect, indifferent effect and antagonistic effect of 6.7%, 63.3%, 30.0% and 0 on the CRAB strains respectively. The MIC₅₀and MIC₉₀of these drugs were significantly lower when they were used in combination with their concentration-accumulative curves shifting to the left. Conclusion Combination of ETM and SCF, ETM and TZP show a synergic and additive inhibitory effect on CRAB strains in vitro.