Abstract: OBJECTIVE To conduct the in vitro drug susceptibility testing of multidrug-resistant and pandrug-resistant Acinetobacter baumannii strains isolated from elderly patients so as to provide reliable theoretical basis for clinical treatment.METHODS The in vitro combined drug susceptibility testing was performed for 114 strains of multidrug-resistant A.baumannii strains isolated from Jan 2012 to Dec 2013 by using agar dilution method.The three combinations included the cefoperazone-sulbactam (SCF) plus polymyxin E (PE), PE plus meropenem (MEM), and minocycline (MH) plus PE.The FIC indices were calculated to judge the combination effects.RESULTS When PE was combined with SCF, 94.7% of the isolates displayed synergism or addition effect, the major effect was addition.When PE was combined with MEM, 99.1% of the isolates displayed synergism or addition effect, about 40.0% of which were synergism.When PE was combined with MH, 99.1% of the isolates displayed synergism or addition effect, the major effect was synergism.There was no antagonism in all of combinations.CONCLUSION PE combined with SCF, MEM, or MH can achieve remarkable effect, and the drug combinations can effectively reduce the MIC of single drug.