Effect of four antibiotics (cefotaxime, ceftazidime, cefepime and ofloxacin) at subinhibitory concentrations (sub-MICs) (1/4, 1/8 or 1/16 of the MICs) on lipase and cell surface hydrophobicity of a clinical isolate of Acinetobacter baumannii 16265 was studied. Lipase activity in the majority of the cases was not significantly changed. Small alterations were drug and concentration dependent. The most efficient ceftazidime at 1/4 of the MIC reduced lipolytic activity to 78.7% of the control value. On the other hand, all b-lactam antibiotics mainly at the highest concentration (1/4 of the MICs) most effectively decreased surface hydrophobicity of the studied strain. Hydrophobicity of treated bacteria evaluated by their adherence to xylene was in the range of 11.2 to 29.9 % of the control values. The most efficient was cefepime. Whether the modifications in potential virulence factors of the bacteria tested observed in in-vitro experiments would have the clinical importance, remains to be evaluated.

        Key words: antibiotics, Acinetobacter baumannii 16265, lipase, hydrophobicity