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Antimicrobial Agents and Chemotherapy, June 2004, p. 1968-1973, Vol. 48, No. 6
0066-4804/04/$08.00+0     DOI: 10.1128/AAC.48.6.1968-1973.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Epigallocatechin-Gallate Enhances the Activity of Tetracycline in Staphylococci by Inhibiting Its Efflux from Bacterial Cells

Research and Development Department, SIFI SpA, 95020 Lavinaio, Catania, Italy

Received 26 September 2003/ Returned for modification 31 October 2003/ Accepted 10 February 2004

Epigallocatechin-gallate (EGCg), the major catechin present in green tea extracts, has been shown to have several antibacterial activities, limiting bacterial growth and invasion and acting in synergy with ß-lactam antibiotics. In this article, we report that EGCg at doses half and below its calculated MIC of 100 µg/ml, is able to reverse tetracycline resistance in staphylococcal isolates expressing the specific efflux pump Tet(K) and appears to improve the MICs of tetracycline for susceptible staphylococcal isolates as well. The visible effect of EGCg is an increased accumulation of tetracycline inside bacterial cells. This effect is likely due to the inhibition of pump activity, and it is evident not only for Tet(K) pumps but also for efflux pumps of a different class [Tet(B)]. In summary, our data indicate that the observed dramatic enhancement by EGCg of tetracycline activity for resistant staphylococcal isolates is caused by impairment of tetracycline efflux pump activity and increased intracellular retention of the drug, suggesting a possible use of EGCg as an adjuvant in antibacterial therapy.

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