La lettre de l'infectiologue 2005; 20(4): 117-126

L'efflux actif des antibiotiques et la résistance bactérienne: état de la question et implications.

Mesaros N., Van Bambeke F., Avrain L., Glupczynski Y., Vanhoof R., Plesiat P., Tulkens P.M.

Unité de Pharmacologie cellulaire et moléculaire, Université catholique de Louvain, Bruxelles, Belgique

The steady increase in bacterial resistance makes the empiric treatment of bacterial infections more and more dificult. Active efflux is now considered as one of the predominant mechanisms that contribute to the decline of antimicrobials. Efflux of potentially toxic substances is, actually, a universal mechanism of protection in every cell, an antibiotics are, most often, opportunistic substrates only. In the present paper, we describe some of the important transport systems responsible for the efflux of major antibiotics in four bacteria of large medical omportance (Staphylococcus aureus, Streptococcus pneumoniae, Escheria coli and Pseudomonas aeruginosa). Because it usually causes only moderate resistance by itself, efflux could be consideredof little importance for the clinician. However, efflux can cooperate with other mechanisms and, thereby, confer higher levels of resistance, can make the process of selection of resistant mutants easier, may be responsible for multiresistance phenotypes in clinical bacterial strains. The latter property results from the fact that most transporters are not very specific of a given chemical structure, but recognise entire families of molecules based on their biophysical properties (amphiphilicity). In addition , transporters are often encoded by mobile genetic elements, which ensure their dissemination among bacterial populations. It is, therefore, important for the clinical microbiology laboratories to detect this mechanism of resistance. The presence of transporters will need to be taken into account for an appropriate choice among potential antibiotics. This is not only important for the individual patient but also for a rational antibiotic policy in the hospital and the community.