Staphylococcus aureus and Escherichia coli adhesion to human cells is reduced by sub-MICs of gemifloxacin.

This study was designed to investigate the capacity of subinhibitory concentrations of the newly developed fluoroquinolone antibiotic gemifloxacin to interfere with the mechanism of bacterial adhesion. Human buccal epithelial cells were incubated with Staphylococcus aureus and Escherichia coli, and grown in the presence of serial dilutions of gemifloxacin from 1/2 MIC to 1/128 MIC. A significant decrease in the adhesion of both S. aureus and E. coli was observed from 1/2 MIC to 1/32 MIC. Morphological changes including filamentous forms of E. coli and cluster formation and swelling of S. aureus were also observed, mainly from 1/2 MIC to 1/8 and 1/16 MIC. These findings are discussed in terms of dose-effect relationships and the interpolation of this pharmacodynamic data with the pharmacokinetics curve of gemifloxacin.