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. 2017 Mar-Apr;33(2):393-397.
doi: 10.12669/pjms.332.11933.

Evaluation of the synergistic effect of a combination of colistin and tigecycline against multidrug-resistant Acinetobacterbaumannii

Ilkem Acar Kaya  1 , Muberra Devrim Guner  2 , Gulcin Akca  3 , Semra Tuncbilek  4 , Aslihan Alhan  5 , Emin Tekeli  6
Affiliations

Evaluation of the synergistic effect of a combination of colistin and tigecycline against multidrug-resistant Acinetobacterbaumannii

Ilkem Acar Kaya et al. Pak J Med Sci. 2017 Mar-Apr.

Abstract

Objective: Acinetobacter baumannii species cause nosocomial infections and can subsequently develop multidrug resistance (MDR). The objective of this study was to evaluate the susceptibility of A. baumannii to a novel combination of colistin and tigecycline, which may provide a faster and more efficacious treatment via a synergistic effect.

Methods: We included 50 MDR A. baumannii samples that were isolated in our clinics between 2009 and 2014. We used broth microdilution (BMD) and the E-test to evaluate the effects of colistin and tigecycline, and the E-test to assess the interaction of the colistin-tigecycline combination. The interaction between the two antibiotics was evaluated using the fractional inhibition concentration (FIC) index and was classified as follows: FIC≤0.5, synergistic; 0.5<FIC<1, partially synergistic; FIC=1, additive; 1<FIC<4, indifferent; and FIC≥4, antagonistic.

Results: No tigecycline and colistin resistance was determined by BMD or E-test. The interaction between colistin and tigecycline, when used in combination, was 2% synergistic, 6% additive, 88% indifferent, and 4% antagonistic.

Conclusion: Although combination therapy is suggested for MDR A. baumannii infections, our results suggest that the synergistic effect of the colistin-tigecycline combination is insufficient to make it an optimal treatment choice.

Keywords: Acinetobacter baumannii; Colistin; Multidrug resistance; Synergy; Tigecycline.

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Conflict of interest statement

Declaration of interest: All of the authors of this manuscript declare that no conflict of interest exists.

Figures

Fig.1
Fig.1
Minimum inhibitory concentrations of colistin and tigecycline measured by broth microdilution & E-test methods.
See this image and copyright information in PMC

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