Involvement of an efflux system in high-level fluoroquinolone resistance of Shigella dysenteriae.

Shigella dysenteriae represent one of the growing list of antibiotic-resistant bacteria. Quinolones are widely employed to treat shigellosis. However, quinolone resistance has already been reported, necessitating an understanding of the mechanisms of development of resistance. We demonstrate that high-level fluoroquinolone resistance of S. dysenteriae exposed to these antibiotics may occur in the absence of gyrA mutations and involve a proton motive force(pmf)-dependent efflux system.