Antimicrobial Resistance in Bacteria: An Overview of Mechanisms and Role of Drug Efflux Pumps

Antimicrobial agents target several essential cellular functions in bacteria including biosynthesis of the cell wall, nucleic acids, and proteins, which consequently produce inhibitory and even lethal effects on bacterial survival. In contrast, bacterial cells possess remarkable capacities to counteract the action of antimicrobials, thus contributing to resistance. The mechanisms of resistance predominantly involve the production of drug-inactivating enzymes, alteration of drug targets, and prevention of drug access; the latter mechanism refers to the function of drug influx and efflux. This chapter provides an overview of molecular and biochemical mechanisms of antimicrobial resistance with an emphasis on the role of drug efflux pumps and their relationship with other key resistance mechanisms in clinically relevant intrinsic and acquired resistance.