Modifying effect of grape skin and red wine extracts on Escherichia coli susceptibility to various antibiotics

Extracts from red wine and grape skin contain a significant amount of polyphenols, including quercetin and resveratrol, and possess high antiradical and chelating ability. Addition of these extracts into E. coli culture causes a 30% inhibition of the growth rate, an induction of antioxidant genes katG and sodA and a rise in H2O2 resistance. Pretreatment of E. coli with the extracts attenuates bactericidal activity of ciprofloxacin and cefotaxim and, in contrast, augments E. coli susceptibility to kanamycin and streptomycin. The extracts may exert their action by influence on the growth rate, redox state of cells and expression of antioxidant genes. In the case of ciprofloxacin, pretreatment with the extracts can decrease DNA damage and the level of the SOS response. The modulating effect of extracts should be taken into consideration in antibiotic therapy.