In vitro synergistic effects of various antibiotic combinations on multiple-drug resistant Acinetobacter baumannii strains

ABSTRACT Aim: Acinetobacter baumannii is a resistant bacteria can cause health care related infections such as bacteremia and ventilator related pneumonia in intensive care units. It has been resistant to many antibiotics due to intensive use of wide-spectrum antibacterial drugs. It is crucial to develop new strategies to defeat this bacteria due to fast growing resistance of A.baumannii to antibiotics and it is taking long time to develop a new antibacterial drug. Multi-drug combination therapies have been proposed in order to overcome these problems in recent years. For this purpose, the in-vitro synergystic effects of four different antibiotic combinations were investigated. Material and Method: Thirty multi-drug resistant A.baumannii strains were included this study. All strains were isolated from samples that isolated from intensive care units of Dicle University Hospital and in between February 2017 and Memorial Dicle Hospital July 2017. Identification of strains were performed with conventional methods and VITEK-2 automated system. Antibiotic sensitivity tests of these strains were also performed by using VITEK-2 Compact (bioMérieux, France) automated system according to suggestions of "European Committee on Antimicrobial Susceptibility Testing (EUCAST)". Microdilution checkerboard method was performed for testing efficacy of antibiotic combinations. Results: Four different antibiotic combinations were tested. The synergistic effects of meropenem-sulbactam combination, ciprofloxacin-rifampicin combination, chloramphenicol-rifampicin combination, and meropenem-rifampicin combination were found %26.6, %26.6, %10 and %6,6 accordingly. Conclusion: Although, in-vitro synergystic effects of meropenem-sulbactam and ciprofloxacin-amikacin combinations aganist multi-drug resistant A.baumannii strains are promising, in vivo studies are neded to better evaluate the response to combination therapies. Because many studies have found different results with same combinations, this study suggest that each hospital should perform its combination tests in certain times by using its own strains. Key Words: Acinetobacter baumannii, multi-drug resistant, synergy testing, microdilution checkerboard