Investigation of Antibacterial Activity of Curcumin and Synergistic Effect with Gentamicin Sulfate

Abstract

Aim: In this study; it was aimed to examine the antibacterial activities and synergistic effects of curcumin, a phytotherapeutic agent, and gentamicin sulfate on bacteria. Materials and Methods: Antibacterial activity of different concentrations of curcumin and gentamicin sulfate on Klebsiella pneumoniae ATCC 13883, Pseudomonas aeruginosa ATCC 27853, Proteus vulgaris ATCC 3851, Bacillus cereus ATCC 11778, Enterococcus faecalis ATCC 29212, Listeria monocytogenes ATCC 7644 and Staphylococcus aureus ATCC 25923 minimal inhibitory concentration (MIC) and tested by disc diffusion methods. The synergistic effects of combinations of curcumin and gentamicin sulfate were examined by checkerboard test. Results: It was found that antibacterial activity was seen in all bacteria and the lowest MIC was 7.81 μg/mL in E. faecalis for curcumin and 0.08 μg/mL in K. pneumoniae for gentamicin sulfate. As a result of the disk diffusion test, inhibition zone diameters were detected at concentrations of 32 and 16 mg/mL in all bacteria tested. As a result of the checkerboard test, an additive effect was observed in four of the bacteria (P. vulgaris, B. cereus, L. monocytogenes, S. aureus) and a indifferent effect was observed in three of them (P. aeruginosa, K. pneumoniae, E. faecalis). The finding of the lowest fractional inhibitor concentration index (FICI=0.75) in B. cereus, one of the gram-positive bacteria, was interpreted as the combination of curcumin and gentamicin sulfate having a partial synergistic effect. Conclusion: This study is the first to evaluate the synergistic effect of curcumin and gentamicin sulfate. Antibacterial activity results suggest that curcumin can be used as an alternative agent in the treatment of bacterial infections. However, in order to clearly determine the effect of both the antibacterial activity of curcumin and its synergy with gentamicin sulfate during the treatment process, these results need to be supported by large-scale in vitro and in vivo studies that will include clinical isolates.

Keywords

• curcumin
• gentamicin sulfate
• antibacterial activity
• synergistic effect
• checkerboard test