The effect of reserpine, a modulator of multidrug efflux pumps, on the in vitro activity of tetracycline against clinical isolates of methicillin resistant Staphylococcus aureus (MRSA) possessing the tet(K) determinant

As part of a screening programme to identify modulators of multidrug efflux in methicillin resistant Staphyloccocus aureus (MRSA), we have validated our assays using the antihypertensive plant alkaloid reserpine. Clinical isolates of MRSA were resistant to tetracycline and shown to possess the tet(K) determinant which encodes for the Tet(K) efflux protein, which conferred high level resistance to tetracycline (MIC = 128 microg/mL). In the presence of reserpine, a known inhibitor of multidrug resistance (mdr) efflux pumps, this MIC was significantly reduced (MIC = 32 microg/mL).