The result showed the maximum resistance for imipenem (100%), meropenem (100%), cefotaxime (98.6%), and ceftazidime (98.6%), and minimum resistance for tetracycline (65.7%) and gentamicin (68.6%). The MCBT test for meropenem-gentamicin-tetracycline antibiotics demonstrated 65.6% and 6.3% of MDR Acinetobacter baumannii strains killed at high and low concentrations of antibiotics, respectively (P=0.04). Besides, 34.4% and 93.8% of MDR Acinetobacter baumannii strains lived at high and low concentrations of meropenem-gentamicin-tetracycline antibiotics, respectively, which were statistically significant (P=0.04). There was a significant relationship between the MIC of gentamicin-meropenem in the combination (Checkerboard) (P=0.0001). Antibiotic interaction effects frequencies were 6.3%, 53.1%, and 40.6% for synergy, incremental, and indifference, respectively. In this study, a significant difference was shown between the FICIs of meropenem (0.68±0.27) and gentamicin (0.003±0.003) (P=0.0001). Also, there was a significant correlation between the FICI factor and the antibiotic's antimicrobial interaction by MCBT (r=0.95, P=0.0001).Conclusion: It seems that the combination of meropenem-gentamicin-tetracycline antibiotics had additive antibacterial effects and could be used to suppress MDR Acinetobacter baumannii isolated.