Efflux-Mediated Drug Resistance in Staphylococcus aureus

Abstract

An intrinsic property of Staphylococcus aureus is that it is naturally susceptible to virtually every antibiotic ever developed. Various mechanisms are responsible for multidrug resistance, but efflux pumps play a crucial role in the emergence of multidrug-resistant bacteria by expelling the antimicrobials from inside the cell. These membrane proteins are also involved in a variety of physiological roles. Therefore, there is a need to identify inhibitors and develop strategies to overcome multidrug resistance. One possible option is the use of efflux pump inhibitors (EPIs) in combination with already available antimicrobial agents/antibiotics. Different approaches have been developed for the evaluation of EPIs, ranging from high-throughput screening to bioassay-guided purification. The greatest hurdle to their clinical use is toxicity, as is the case for the existing EPIs, verapamil and reserpine. To date, no single EPI has been approved for use in clinical settings because of uncertainty around their potency and their intolerable adverse effects, particularly inhibition of cytochrome P450. Currently, the use of test active EPIs is limited to epidemiological studies. However, the search for more specific and effective EPIs will continue because of their significant benefits. The development of new chemotherapeutic agents requires contemplation of efflux pump substrate selectivity.