In vitro effect of ampicillin/sulbactam on Acinetobacter species.

The effects of subinhibitory concentrations (sub-MIC) of ampicillin/sulbactam (AMP/sulbactam), on the surface hydrophobicity and the lipase activity of ten Acinetobacter strains, were examined. The alterations in the activities studied were strain and drug concentration dependent. Most of the strains treated showed a decrease in surface hydrophobicity to a different extent. The hydrophobic character of three strains exposed to 1/4 or 1/8 of the MIC of the antibiotic was changed to a hydrophilic state. The majority of Acinetobacter strains after treatment with antibiotic possessed increased lipolytic activity. AMP/sulbactam even at sub-MIC may interfere with possible virulence factors of Acinetobacter strains in vitro.