ACTIVE EFFLUX SYSTEMS IN PSEUDOMONAS-AERU GINOSA

Three active efflux systems have been described in Pseudomonas aerugin osa: namely, MexA-MexB-OprM, MexC-MexD-OprJ, and MexE-MexF-OprN. Each of these systems consists of 3 proteins, one of which is a broadly-spe cific transporter able to accommodate a variety of amphiphilic substra tes. Over-expression of the efflux system, consecutive to mutations in regulator genes, enhances the resistance levels of the organism (MICs x 4 to 8-fold) to structurally unrelated antibiotics such as quinolon es, tetracyclines, chloramphenicol, trimethoprim, and various beta-lac tams. Therapeutical impact of multidrug resistance remains to be inves tigated.