Objective: Pseudomonas aeruginosa causes respiratory tract infections that are difficult to treat in patients with cystic fibrosis because of the antibiotic resistance mechanisms and virulence factors. Curcumin has been found to possess antibacterial as well as antitumoral and anti-inflammatory effects. The aim of this study was to investigate the effect of curcumin on several virulence factors (biofilm, elastase, alkaline protease) of P. aeruginosa isolates which were obtained from respiratory tract samples of cystic fibrosis patients.

Material and Methods: In our study, minimal inhibitory concentration (MIC) values of curcumin for P. aeruginosa isolates (n=65) were determined by agar dilution method. Production of three different virulence factors (elastase, alkaline protease, and biofilm) were investigated by semi-quantitative methods which relied on the measurement of absorbance in microtiter plates. The isolates which had a positive virulence factor production were retested for the production of virulence factors at the presence and absence of sub-MIC curcumin concentrations simultaneously and measured absorbance values were compared statistically.

Results: In our study, curcumin MICs of the 11 (16%) isolates were 250-500 μg/ml 501-1000 μg/m for 7 (11%), 1001-1500 μg/ml for 5 (8%), and above 1500 μg/ml for 42 (65%) isolates. Out of 65 isolates in 54% biofilm, in 74% elastase, and in 68% alkaline protease production were positive. In terms of virulence factor production, results didn’t indicate a statistically significant difference between the absorbance values obtained with and without exposure to sub-MIC concentrations of curcumin.

Conclusion: In conclusion, there was no statistically significant decrease in the virulence factors of cystic fibrosis isolates which were once exposed to in vitro curcumin. However, because curcumin is a non-toxic, anti-inflammatory and anti-bacterial agent, it will be suitable to investigate the in vivo effects of longterm curcumin use in these patient groups.