Combined effect of a natural flavonoid rutin from Citrus sinensis and conventional antibiotic gentamicin on Pseudomonas aeruginosa biofilm formation

Extensive and irrational use of antibiotics to treat biofilm associated infections has led to the emergence of multiple drug resistant (MDR) strains. Rutin, a vitamin P rich fiavonoid group of phytochemical with antimicrobial property, has been studied for its anti-biofilm potential against Pseudomonas aeruginosa, which is a model biofilm forming pathogenic bacterium, in combination with conventional antibiotic gentamicin. For this study, rutin was isolated from the peels of Citrus sinensis by column chromatography and HPLC and characterized by UV-vis and FT-IR spectral analyses. Results showed that rutin exhibited minimum inhibitory concentration (MIC) at 800 mu g/ml against the bacterium. Its anti-biofilm potential was examined by crystal violet staining, protein analysis, microscopy studies and quantification of exopolysaccharide (EPS) using several sub-MIC doses. The inhibition of biofilm formation was synergistically enhanced when the bacterium was treated with rutin (200 mu g/ml) along with an antibiotic gentamicin (2.5 mu g/ml). EPS production was responsible for adherence and maturation of biofilms, which was also significantly reduced in the tested strain. To the best of our knowledge, this is the first study describing the anti-biofilm potential of citrus fiavonoid rutin as well as its synergistic effects when combined with gentamicin against P. aeruginosa. Findings of the study substantiate that rutin can be potentially used as an adhesion inhibitor for the treatment of P. aeruginosa infections. (C) 2018 Elsevier Ltd. All rights reserved.