Influence of the postantibiotic effect and postantibiotic sub-MICs effect of netilmicin, tobramycin, ciprofloxacin and pefloxacin on alginate production by Pseudomonas aeruginosa.

The postantibiotic effect (PAE) (postantibiotic phase induced by 2x or 4x MIC) as well as the postantibiotic effect of subinhibitory concentrations (0.1x, 0.2x and 0.3x MIC) (PA SME) of netilmicin, tobramycin, ciprofloxacin and pefloxacin affected the production of the virulence factor alginate by a P. aeruginosa strain. Aminoglycosides and ciprofloxacin at a concentration of 4x MIC inhibited the alginate production more significantly than 2x MIC. Suprainhibitory concentrations of aminoglycosides were more effective than pefloxacin (2x or 4x MIC) and ciprofloxacin (2x MIC). PA SME demonstrated by the above antibiotics (with the exception of ciprofloxacin 2x MIC + 0.1x MIC) suppressed alginate production more efficiently.