Effect of amikacin on cytotoxic activity and hydrophobicity of Acinetobacter baumannii

Abstract

Effect of amikacin at suprainhibitory (2 or 4 x MIC) or supra-subinhibitory concentrations (2 or 4 x MIC + 0.2 x MIC) on bacterial growth, cytotoxicity and cell surface hydrophobicity of three Acinetobacter baumannii strains was studied. Amikacin at suprainhibitory concentrations induced postantibiotic effects (PAEs; suppression of bacterial growth after short time exposure of bacteria to the antibiotic) against all A. baumannii strains. PAEs ranged from 1.2 to 2.9 h (2 x MIC) and 3.5 to 6.3 h (4 x MIC). Supra-subinhibitory concentrations of amikacin (2 x MIC + 0.2 x MIC) manifested a more significant delay of bacterial regrowth (PA SMEs) for two strains (6.6 or 7.5 h) in comparison with PAEs. One strain under these conditions as well as all strains treated with amikacin at 4 x MIC + 0.2 x MIC did not show any regrowth. Amikacin at all concentrations tested significantly reduced cytotoxic activity of A. baumannii evaluated on alveolar epithelial type II cells. Survival of type II cells after application of antibiotic-treated A. baumannii was in the range of 88 to 101% of the control cells. Cell surface hydrophobicity of amikacin-treated bacteria was practically unchanged varying between 94 and 100.9% as compared to the controls.