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Fukugiside, a biflavonoid from Garcinia travancorica inhibits biofilm formation of Streptococcus pyogenes and its associated virulence factors

Purpose. Streptococcus pyogenes, a notorious human pathogen thatis responsible for various invasive and non‐invasive diseases, possesses multiple virulence armaments, including biofilm formation. The current study demonstrates the anti‐biofilm and anti‐virulence potential of fukugiside, a biflavonoid isolated from Garciniatravancorica, against S. pyogenes. Methodology. The anti‐biofilm activity of fukugiside was assessed and established using microdilution and microscopic analysis. Biochemical assays were performed to assess the effects of fukugiside on important virulence factors, which were further validated using quantitative real‐time PCR and in vivo analysis in Caenorhabditis elegans. Results. Fukugiside exhibited concentration‐dependent biofilm inhibition (79 to 96 %) against multiple M serotypes of S. pyogenes (M1, M56, M65, M74, M100 and st38) with a minimum biofilm inhibitory concentration of 80 &mgr;g ml−1. Electron microscopy and biochemical assay revealed a significant reduction in extracellular polymeric substance production. The results for the microbial adhesion to hydrocarbon assay, extracellular protease quantification and differential regulation of the dltA, speB, srv and ropB genes suggested that fukugiside probably inhibits biofilm formation by lowering cell surface hydrophobicity and destabilizing the biofilm matrix. The enhanced susceptibility to phagocytosis evidenced in the blood survival assay goes in unison with the downregulation of mga. The downregulation of important virulence factor‐encoding genes such as hasA, slo and col370 suggested impaired virulence. In vivo analysis in C. elegans evinced the non‐toxic nature of fukugiside and its anti‐virulence potential against S. pyogenes. Conclusion. Fukugiside exhibits potent anti‐biofilm and anti‐virulence activity against different M serotypes of S. pyogenes. It is also non‐toxic, which augurs well for its clinical application.