Postantibiotic effects were induced in Pseudomonas aeruginosa clinical isolates after a short time (1 hr) treatment with 2X-and 4X-MICs of different antimicrobial agents (fluoroquinolones, amikacin, aztreonam, and β-lactam antibiotics). The postantibiotic effect of fluoroquinolones on bacterial regrowth and virulence factor activity were more than that of the amikacin, and the highest postantibiotic effect was observed with norfloxacin. The postantibiotic effect of fluoroquinolones at

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... ions of 2X MICs induced suppression in the Pseudomonas aeruginosa elastase, protease, and phospholipase C activity to the ranges of 31-37%, 62-69.8%, and 62.4-68.8% of the control, respectively. While at higher concentrations (4X MICs), they reduce the enzymatic activity to the ranges of 17-20%, 30.6-36%, and 47.6-57% of the control, respectively. In the case of amikacin, the induced postantibiotic effects at concentrations of 2X and 4X MIC caused suppression in the Pseudomonas aeruginosa enzymatic activity to the ranges of 54-73.8% and 27-59.2% of the control, respectively. The postantibiotic effect of aztreonam and β-lactam antibiotics induced weak effect on the re-growth and virulence factors activity of the tested isolates. According to the obtained results, the postantibiotic effect of fluoroquinolones and amikacin induced significant suppression in the Pseudomonas aeruginosa elastase, protease, and phospholipase activity.