The laboratory has identified 2 families of molecules inhibiting bacterial efflux pumps and showing or not an additional antibacterial activity. These new molecules potentiate fluoroquinolone activity (ciprofloxacine and norfloxacine) by inhibiting NorA efflux pumps of Staphylococcus aureus and Enterococcus faecalis. Easily obtained in large quantities, they are derived from flavonoids which are non toxic natural compounds of vegetal origin. Quantities of antibiotics will be decreased when used in association with these new inhibitors and treatment’s effectiveness even against GRAM+ resistant bacteria will be strengthened. Emergence of multidrug resistant bacterial strains will be slowed down.