The postantibiotic effect (PAE) and postantibiotic effect of subinhibitory concentration (PA SME) of gentamicin as well as influence of these pharmacodynamic parameters on surface hydrophobicity of three Acinetobacter baumannii strains were studied in vitro. Suppression of bacterial growth (PAE) after a short time exposure of bacteria to gentamicin (30 min) at suprainhibitory concentra - tion 2x MIC was in the range of 0.6 h to 3.4 h. Longer PAE was observed after treatment of bacteria with gentamicin at 4x MIC (1.5 h – 5.1 h). Supra-subinhibitory concentrations of gentamicin (2x or 4x MIC + 0.2x MIC) caused still more effective delay of bacterial regrowth (PA SME) in comparison with suprainhibitory concentrations for one strain (9.1 h and 9.6 h) and in the case of further two strains they were so efficient that regrowth of bacteria was not observed for 24 h. Surface hydrophobicity of the gentamicin treated strains evaluated by adherence of bacteria to xylene ranged from 90.0% to 99.7% of the control values (without antibiotic).

        Key words: gentamicin – pharmacodynamic parameters – Acinetobacter baumannii – surface hydrophobicity