Abstract

Background: Multiple-drug resistance of Acinetobacter species cause difficulties in the treatment of infections. Due to decrease in success rates with monotherapy combinations that show synergistic effect in the treatment of MDR Acinetobacter infections is used. Objectives: The study aimed to investigate the efficacy of meropenem and amikacin combinations against metallo-beta-lactamase (MBL)-producing Acinetobacter strains isolated from clinical specimens. Method: The presence of MBL in strains was detected by gradient diffusion method (GDM). Fifty MBL-positive and 50 MBL-negative strains were included in the study. The activity of meropenem-amikacin combination against MBL-positive isolates was investigated by both GDM and the checkerboard method while the activity against MBL-negative isolates was investigated by the checkerboard method. Results: Additive or indifferent interactions between meropenem and amikacin were detected in 38 (76%) of the 50 MBL-positive strains, synergistic interactions were detected in 7(14%), and antagonistic interactions were detected in 5(10%) using GDM. Using the checkerboard method, additive or indifferent interactions between the drugs were detected in 37 (74%) and synergistic interactions in 13 (26%) of 50 MBLpositive strains while synergistic interactions were observed in 36 (72%) and additive or indifferent interactions in 14 (28%) of 50 MBL-negative strains. No antagonistic interaction was detected in the MBL-positive and MBL-negative strains using the checkerboard method. In MBL-positive strains no difference was found between the results of checkerboard and GDM. Conclusion: Based on our detection of 72% synergistic interactions between meropenem and amikacin on MBL-positive strains in the Gold Standard checkerboard assay, it is concluded that in vitro evidence supports meropenem and amikacin combination therapy against non–MBLproducing Acinetobacter spp. but further clinical studies are needed.

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