Pharmacodynamic parameters of aminoglycosides and their effect on exoenzymes of Pseudomonas aeruginosa.

Aminoglycosides at 2x or 4x minimum inhibitory concentration induced postantibiotic effects against Pseudomonas aeruginosa lasting 3.5-4.9 h (gentamicin) and 0.5-3.7 h (selemycin). Postantibiotic effects of subinhibitory concentrations of the aminoglycosides tested were substantially longer. Some combinations of supra- and subinhibitory concentrations of antibiotics did not even allow any regrowth of the bacterial strain. The postantibiotic effects and postantibiotic effects of subinhibitory concentrations of gentamicin and selemycin were associated with changes of P. aeruginosa elastase and proteinase. Combinations of supra- and subinhibitory concentrations more pronouncedly suppressed enzymic activities than did suprainhibitory concentrations alone.