Objectives: There is an increasing incidence of Acinetobacter species causing serious nosocomial infections such as bacteremia, urinary tract infections, meningitis, skin and soft tissue infections and pneumonias with high mortality rate of 30-75% in hospitalized patients especially intensive care units (ICUs). During the past decade, multi drug resistant (MDR)/pan drug resistant (PDR) Acinetobacter strains have presented a real challenge to clinicians and are posing difficulties in treatment. Carbapenem-resistant Acinetobacter  species  particularly A. baumannii, represent a growing public health concern, since they often confer resistance to other critically important antimicrobials, including amino glycosides, fluoroquinolones or even polymyxins.

Methods: In the present study, various antibiotic combinations such as colistin + meropenem, imipenem + tigecycline, polymyxin B + azithromycin and doripenem + sulbactam are used for MDR/PDR Acinetobacter infections and tested for in-vitro synergy by Etest and Micro dilution checkerboard (MCB) and confirmed by time kill assay.

Results & Conclusions: this study we found synergistic results with all three methods used in study with all three combinations significantly but with one combination i.e. doripenem+sulbactam, we found synergy only with Etest not with MCB and time kill assay. Related to outcome of patients with respect to the treatment received during hospital stay, we did not found significant difference both the groups, (two drug regimen & three drug regimen) regarding their mortality.

Keywords: Acinetobacter species, Synergy, Epsilometric test, Mircodilution checkerboard, Timekill assay

Abbreviations: CRAB- Carbapenem Resistant Acinetobacter baumannii, Etest- Epsilometric test, MCB- Microdilution Checkerboard Method, TKA- Time Kill Assay