The present invention discloses a universal activity enhancer for antibiotic compositions in form of a phytocompound carnosol. The compound acts as an Efflux Pump Inhibitor (EPI) which when added to various antibiotic compositions, helps to overcome multidrug resistance (MDR). The compound is extracted from the leaves of Rosmarinus officinalis. The compound when used with standard antibiotic compositions, significantly enhanced their activity and helped to overcome bacterial resistance. Potentiation was obtained with ciprofloxacin, tetracycline, erythromycin and gentamycin against Salmonella typhimurium, and with ciprofloxacin and gentamycin against Escherichia coli, a frequent cause of life threatening blood stream infections and others such as Urinary tract infections (UTI).
