Effects of sub-minimum inhibitory concentrations of gatifloxacin on the inhibition of Staphylococcus aureus and Escherichia coli adherence. 
The aim of this study was to investigate the capacity of subinhibitory concentrations of the newly developed fluoroquinolone antibiotic gatifloxacin (CAS 160738-57-8) to interfere with the mechanism of bacterial adhesion.  Human buccal epithelial cells were incubated with different strains of both Staphylococcus aureus and Escherichia coli, grown in the presence of subinhibitory gatifloxacin concentrations varying from 1/2 MIC (minimum inhibitory concentration) to 1/128 MIC.  A significant decrease was observed in the adherence of S. aureus and E. coli to buccal cells at drug MICs of 1/2 to 1/32 and 1/2 to 1/64, respectively.  A large number of filamentous forms of different lengths and shapes were observed in the case of E. coli, whereas there was an abnormal increase in the diameter of the cells in the case of S. aureus.  The interpolation of these pharmacodynamic findings with the pharmacokinetic curve indicate that the effect of subinhibitory concentrations of gatifloxacin can prolong its antimicrobial effects against S. aureus and E. coli for as long as 30 h and 37 h, respectively, after the MIC values have been reached.