Influence of sub-inhibitory concentrations of antibacterials on the surface properties and adhesion of Escherichia coli.

The effect of sub-inhibitory concentrations of antibacterials, including quinolones, on the surface properties of a uropathogenic strain of Escherichia coli was examined. The effect on the charge and hydrophobicity of the cell surface was assessed by means of partition between two aqueous phases, polyethylene glycol and dextran. Antibiotics at 1/8 x MIC inhibited adhesion to uroepithelial cells, and induced an increase in bacterial charge and hydrophobicity. Inhibition of adhesion correlated with increased charge, but not with hydrophobicity. The influence of magnesium on the inhibition of adhesion by sub-MICs of pefloxacin was also investigated. Loss of the anti-adhesive property of pefloxacin was observed with increasing magnesium concentrations, suggesting that quinolones should be free from magnesium to induce an inhibition of adhesion. Examination by electron microscopy showed a disappearance of fimbriae following treatment of E. coli cells with 1/8 x MIC of pefloxacin.