Suppression of bacterial growth in seven strains of the Acinetobacter species after 30min treatment with tobramycin at suprainhibitory concentrations (postantibiotic effect – PAE) and at supra-subinhibitory concentrations (postantibiotic effect of subinhibitory concentrations – PA SME) as well as changes in surface hydrophobicity and in the production of lipase and histamine in the exposed strains were studied. Pharmacodynamic parameters (PAE and PA SME) as well as changes in bacterial characteristics tested were dependent on antibiotic concentration and on the strain used. Suppression of bacterial growth after treatmentwith tobramycin at 2xMICwas in a range of 0.6–4.5 h, a higher concentration (4x MIC) induced a longer PAE (1.9–5.4 h). Tobramycin at supra-subinhibitory concentratinos (2xMIC + 0.2xMICand 4xMIC+ 0.2x MIC) caused total suppression of bacterial growth. In the majority of the tobramycin-treated strains, an increase in hydrophobicity manifested by adherence of bacteria to xylene as well as an increase in lipolytic activity was observed. Tobramycin at the concentrations tested did not affect the production of histamine.

        Key words: tobramycin – postantibiotic effect – Acinetobacter spp. – hydrophobicity – lipase – histamine