β-Sitosterol Glucoside—A Novel Inhibitor of Escherichia coli O157:H7 Biofilm and Motility

Citrus is a storehouse of bioactive compounds with health maintaining properties. In the present report, β-sitosterol glucoside, bergamotin and imperotorin were purified from Poncirus trifoliata and evaluated for their potential to inhibit E. coli O157:H7 (EHEC) biofilm formation and motility. The EHEC was identified in the 1980s and since then it has become one of the major food-borne pathogen. The CDC advises against using antibiotics for EHEC infections and the treatment options are limited to preventive measures. Therefore, to control and prevent the EHEC infections, novel antimicrobials are required. The β-sitosterol glucoside demonstrated a very potent inhibition of EHEC bifilm formation. In addition, EHEC motility, measured until 24 h, was completely inhibited by the β-sitosterol glucoside. Since flagella is a major determinant in biofilm and motility, role of flagellar master regulator flhDC was assessed using genetic analysis. The investigations revealed that the effect of β-sitosterol glucoside is dependent upon flhDC. In addition, β-sitosterol glucoside seems to exert its effect, without altering the growth rate. The results indicate that β-sitosterol glucoside may influence EHEC pathogenesis and contribute to the beneficial effects of citrus. This project is based upon the work supported by the USDA-CSREES # 2009-34402-19831 and USDA-NIFA-2010-34402-20875 "Designing Foods for Health" through the Vegetable & Fruit Improvement Center.