Dear Colleagues,

Multi-drug resistance of pathogenic bacterial clinical isolates is now known to be mainly due to over-expressed efflux pumps that result from therapy with antibiotics that is either ineffective or improperly administered [1]. The development of the MDR phenotype is thus problematic to therapy since resistance to the antibiotic initially used also bestows resistance to antibiotics of the same class and or other classes of antibiotics [1,2]. For the past two decades, much has been learned about the regulation and control of efflux pumps that render the clinical isolate with an MDR phenotype. Nevertheless, at this time, although many compounds have been identified to affect the activity of the over-expressed efflux pump of a given MDR bacterium and therefore render the antibiotic bacterium susceptible to antibiotics to which it was initially resistant, none have yet to reach the market as adjuncts to antibiotic therapy. The special issue of “Antibiotics” "Efflux pumps of multi-drug resistant pathogenic bacteria: Their genetic regulation, molecular biology and possible control with newly designed agents." will receive contributions from experts in the field of efflux pumps, their regulation and potential control with newly discovered agents from natural and chemically derived sources. We hope that those who are conducting research in this area will also submit their contributions for publication in this special issue.

1. Amaral, L.; Fanning, S.; Pagès, J.M. Efflux pumps of gram-negative bacteria: Genetic responses to stress and the modulation of their activity by pH, inhibitors, and phenothiazines. Adv. Enzymol. Relat. Areas Mol. Biol. 2011, 77, 61–108. Review.
2. Pagès, J.M.; Amaral, L. Fanning, S. An original deal for new molecule: Reversal of efflux pump activity, a rational strategy to combat Gram-negative resistant bacteria. Curr. Med. Chem. 2011, 18, 2969–2680.

Prof. Dr. Leonard Amaral
Guest Editor