Antimicrobial activity and postantibiotic effect of flurithromycin againstHelicobacter pylori strains

The minimal inhibitory concentrations (MIC) of flurithromycin on 49 clinica l isolates of Helicobacter pylori was investigated. The MICs were determine d using an agar dilution technique. Flurithromycin inhibited the growth of H. pylori strains with MIC50 and MIC90 values of 0.156 and 0.625 mg/l, resp ectively. The postantibiotic effects (PAE) were studied on ten strains, by exposure of the bacteria to flurithromycin at five and ten times MIC for 1 or 2 h. Regrowth was determined by measuring the viable counts after drug r emoval by a 10(3) dilution procedure. All PAEs increased as a function of c oncentration and time of exposure. The mean duration of PAEs varied between 1.5 and 6 h. These data are encouraging since macrolides play a key role i n the clinical treatment of H. pylori infections, and the strong PAE caused by flurithromycin may contribute to the in vivo efficacy of this drug. (C) 2001 Published by Elsevier Science B.V. and International Society of Chemo therapy. All rights reserved.