POSTANTIBIOTIC EFFECT AND VIRULENCE FACTORS DEPRESSION INDUCED BY CIPROFLOXACIN AND BY AMINOGLYCOSIDES IN A CLINICAL ISOLATE OF PSEUDOMONAS-AERUGINOSA

The postantibiotic effect (PAE) was induced in Pseudomonas aeruginosa by ciprofloxacin, tobramycin and netilmicin (2 x or 4 x MIC). A longer PAE was evoked by a higher concentration of antibiotics. The evaluati on of Pseudomonas aeruginosa virulence factors after treatment with su prainhibitory concentrations of the antibiotics tested showed that a h igher suppression of elastase activity was associated with a longer PA E. Elastase was suppressed more effectively than proteinase. The highe st reduction of elastase and proteinase activity (to 24.9% and 76.4% o f the control values) was observed after treatment with ciprofloxacin.