Investigation of antibacterial activity of curcumin and synergistic effect with gentamicin sulfate

The widespread use of antibiotics, which are preferred in the treatment of bacterial infections, leads to the emergence of multi-drug resistant bacterial strains. This situation complicates the treatment of infections and leads to the search for bioactive products that can be used in addition to or as an alternative to classical antibiotic therapy in order to prevent resistance. In this study; The antibacterial activity of curcumin, a phytotherapeutic agent, and gentamicin sulfate on Gram-negative (Klebsiella pneumoniae ATCC 13883, Pseudomonas aeruginosa ATCC 27853, Proteus vulgaris ATCC 3851) and Gram-positive (Bacillus cereus ATCC 11778, Enterococcus faecalis ATCC 29212, Listeria monocytogenes ATCC 7644, Staphylococcus aureus ATCC 25923) bacteria was investigated. In addition to the effects of curcumin alone, the synergistic effects of curcumin when combined with gentamicin sulfate were also investigated. Minimum inhibitory concentration and disk diffusion test were performed to determine antibacterial activity. The checkerboard method was used for the synergistic effect study. In our study; as a result of the minimum inhibitory concentration test, it was found that antibacterial activity was seen in all bacteria and the lowest concentration was 7.81 µg/ml in E. faecalis for curcumin and 0.08 µg/ml in K. pneumoniae for gentamicin sulfate. Inhibition zone diameters of 32 and 16 mg/ml concentrations were determined in all bacteria tested as a result of the disk diffusion test. As a result of the checkerboard test of the combination of curcumin and gentamicin sulfate, additive effects were observed in four of the bacteria (P. vulgaris, B. cereus, L. monocytogenes, S. aureus) and an indifferent effect was observed in three (P. aeruginosa, K. pneumoniae, E. faecalis). Finding the lowest fractional inhibitory concentration index (FICI=0.75) in B. cereus, one of the Gram-positive bacteria, was interpreted as the partial synergistic effect of the combination of curcumin and gentamicin sulfate. In conclusion; in order to clearly determine the effect of curcumin and gentamicin sulfate synergy in the treatment process of bacterial infections, our results should be supported by large-scale in vitro and in vivo studies in which clinical strains will be included. In addition, this study is the first to evaluate the synergistic effect of gentamicin sulfate and curcumin. The use of different natural therapeutic agents together with antibiotics in the empirical treatment of bacterial infections seems promising in terms of reducing the toxicity of antibiotics and increasing their antimicrobial activity. Keywords: Curcumin, Gentamicin sulfate, Antibacterial activity, Synergistic effect.