Tannic Acid as Phytochemical Potentiator for Antibiotic Resistance Adaptation

The effect of phytochemical tannic acid on Methicillin Resistant Staphylococcus aureus (MRSA) three clinical strains was studied individually and in combination with western antibiotic fusidic acid. The two drugs were synergistic to each other and the combined effect of the two drugs could delay or prevent the occurrence of adaptive mutations in MRSA. The possible mechanism might be the phytochemical tannic acid could potentiate the effect of fusidic acid and/or acts alternative target that results in lysis of bacteria. In this study, it was found that the mutants result from the continuous exposure of sub-minimal inhibitory concentration (MIC) of fusidic acid revealed over active efflux pump as measured by ethidium bromide (EtBr) accumulation assay. However, the parent strains have no efflux pump activity. Therefore, it can be concluded that the strains which normally don’t have efflux activity can result in over activity of efflux pump if they are being exposed by sub-MIC concentrations of western antibiotic (fusidic acid). Efflux modulating activity of tannic acid was tested against the strains with over active efflux pump activity. It was noticed that EtBr accumulation was increased with over time when the adapted strains were being exposed by sub-MIC concentrations (0.3 and 0.6 MIC) of tannic acid, meaning that phytochemical tannic acid has efflux modulating activity against MRSA strains that results in decreased in MIC of partner drug and thus, preventing its adaptive mutation.