Evaluation of multidrug-resistant Acinetobacter baumannii isolates in terms of sensitivity to combination of antibiotics including colistin and rifampin, cefotaxime and amikacin, imipenem and colistin

Abstract

Acinetobacter baumannii is a Gram-negative, non-fermenting bacterium that is frequently isolated from nosocomial infections. The organism is resistant to most classes of antibiotics, and limited options are available to treat infections caused by this organism. One of the treatment options to overcome the resistant strains of this organism is antibiotic trerapy using a combination of two or more different antibiotics. The purpose of this study was to investigate the effects of combinations of colistin + rifampin, cefotaxime + amikacin and imipenem + colistin in laboratory conditions against carbapenem resistant A. baumannii isolates. Methods: Clinical specimens were inoculated on specific growth medium and bacterial isolates were identified using standard microbiological methods. Antibiotic resistance pattern of studied isolates was determined by disk diffusion method and minimum inhibitory concentration was determined by microbroth dilution method. The synergistic effects of the studied compounds were determined by determining the FIC index using the CheckerBoard method. Results: In the present study, high levels of antibiotic resistance were observed. None of the studied isolates were resistant to colicitin. Antimicrobial effects of antagonism were not observed in any of the compounds. The most synergistic effects were in the combination of amikacin and cefotaxime and in 9 of 12 isolates.