Multidrug-resistant Acinetobacter baumannii infection has presented a global medical challenge. The antibiograms of paired colistin-susceptible and -resistant strains revealed increased susceptibility of colistin-resistant strains to most tested antibiotics, including those that are active against only gram-positive bacteria. Synergy between colistin and rifampicin was observed in the colistin-susceptible strains. The ability to form biofilm in the colistin-resistant strains was significantly lower (P<.001) than in the parent strains. Our study provides valuable information for potential expansion of our current therapeutic options against colistin-resistant A. baumannii infection.