In vitro drug interactions of gallates with antibiotics in Staphylococcus Aureus

Abstract

The antimicrobial activities of tetracycline, mupirocin, and fusidic acid are tested in combination with Epicatechin Gallate (ECG), and Ethyl Gallate (EG) using 2 Methicillin resistant (MRSA) and 2 Methicillin sensitive (MSSA) strains of Staphylococcus aureus. Sub-inhibitory concentration of EG at 256mg l -1 is found to be synergistic when used in combination with tetracycline, mupirocin, and fusidic acid; and a sub-inhibitory concentration of ECG at 32 mg l-1 is found to be synergistic with tetracycline in all the four Staphylococcus aureus strains tested. The synergistic combinations reduce the MICs of all the above three antibiotics by 4 fold. Combining ECG at 32mg l-1 with mupirocin, reduces the MIC of mupirocin by four fold in MSSA C1 strain. 74% of the combinations show consistent results in both time-kill assay and checkerboard method. The identified combinations may lead towards novel therapeutic interventions for treating MRSA infections.