Subinhibitory concentrations of antibacterial drugs and Pseudomonas aeruginosa virulence factors.

Pseudomonas aeruginosa is an important, opportunistic pathogen responsible for nosocomial infections in the immunocompromised host and resistant to antibacterial drugs. Its pathogenicity is related to many virulence factors such as proteases, alginate, exotoxin A and exoenzyme S. Our previous study showed a down-regulation of some P. aeruginosa virulence factors by subinhibitory concentrations of antibacterial drugs. This study aimed to compare the effects of subinhibitory concentrations of a new difluoroquinolone, PD 131,628, a betalactam, aztreonam and an aminoglycoside, netilmicin.