FACTORS INFLUENCING THE UPTAKE OF NORFLOXACIN BY ESCHERICHIA-COLI

The effect of cyanide, arsenate, Mg++ or EDTA on the uptake of norfioxacin in Escherichia coli was measured. Uptake of norfloxacin was suppressed by either 0.1 mM MgSO4 or 0.1 mM EDTA, while the presence of 0.1 mM MgSO4 increased the minimum suppressive concentration of EDTA from 0.1 to 0.2 mM. Increased uptake in the presence of 10 mM cyanide was observed, but the addition of 10 mM arsenate had no significant effect. Concentration of norfioxacin in bacterial cells was observed even when uptake was suppressed by the addition of 10 mM EDTA. Uptake in mini-cells was comparable to that in whole cells. These results suggest that the uptake of norfioxacin in E. coli, in addition to influx by simple diffusion and energy-dependent efflux, is influenced by binding of norfioxacin to the cell surface as a result of chelating activity to Mg++, together with an unknown concentration step resulting from binding to cell components other than the chromosome. © 1991 The British Society for Antimicrobial Chemotherapy.