[The active efflux pump in antimicrobial resistance].

Active efflux of antibiotics is one of the different resistance mechanisms of bacteria against antimicrobial agents. The rapid exit of the antibiotic from the bacteria prevents its interaction with target point. This mechanism, also known as active efflux pump, is very important since it can explain the simultaneous resistance to several antibiotic families. There are four main active efflux systems: MFS, RND, Smr and ABC. This review includes all of them, together with their transporting proteins, the bacteria that have those proteins and the phenotype of the antibiotics affected. The complex genotype regulation systems, including codifying genes, positive and negative regulators, chromosomal or plasmidic localization is also studied. Finally, the causes of marked resistance to antimicrobial agents of isolated strains in the clinic, especially in hospital areas are revised. The role of the European Antimicrobial Resistance Surveillance System (EARSS) in the evaluation of those resistances is discussed.