Synergistic activity of meropenem and sulbactam against carbapenem-resistant Acinetobacter baumannii

OBJECTIVE: The purpose of this study was to determine the in vitro synergistic effect of meropenem and sulbactam drug combinations through checkerboard assay against Carbapenem-resistant Acinetobacter baumannii (CRAB) to establish potential treatment options. MATERIALS AND METHODS: CRAB was cultured from the clinical samples of Endotracheal aspirate, blood, pus, throat swab, and urine specimens from 80 patients with suspected nosocomial infection in 1 year. Minimum inhibitory concentration (MIC) was determined for meropenem and sulbactam drugs individually. Synergism was determined for meropenem + sulbactam combinations using checkerboard assay. RESULTS: All the 80 CRAB isolates were found to be resistant (>16 MIC) for Meropenem drug and 64 out of 80 showed resistant (>16 MIC) to sulbactam, 14 isolates displayed intermediate (8 MIC), and 2 of them were found to be sensitive (<2 MIC). The checkerboard assay showed 66.25% of synergism between meropenem and sulbactam followed by 25% of additivity and 8.75% of them were found to be indifferent. CONCLUSION: In the current checkerboard assay, we observed potential synergistic activity between meropenem and sulbactam against CRAB isolates which indicates that this combination can be an appealing strategy in the treatment of nosocomial infections caused by CRAB isolates.