Inhibitory and bactericidal activity of rokitamycin against Helicobacter pylori and morphological alterations

Rokitamycin is a macrolide antibiotic, recently entered into clinical use. Its in vitro activity and kill kinetics against Helicobater pylori have been evaluated at 1 x the minimum inhibitory concentration (MIC), 2 x MIC and 4 x MIC at 2, 4, 8, 24 hours and compared with those of clarithromycin, erythromycin and amoxicillin. Morphological changes in H. pylori induced by rokitamycin incubation at these MICs and times were also investigated by scanning electron microscopy. All the antibiotics tested had good inhibitory activity against H. pylori, a slow growing microorganism. The order of MIC activity was clarithromycin > amoxicillin > rokitamycin > erythromycin. Rokitamycin killed more rapidly than the other antibiotics, in fact H. pylori strains were totally killed at 8 h (2 x MIC) and 4 h (4 x MIC) and after only 2 h incubation all concentrations greatly decreased the CFU/ml. These effects were also confirmed by the rapid appearance of surface and morphological alterations (focal blebs, constrictions, rounded forms) in the normal structure of H. pylori observed by scanning electron microscopy. Clinical studies should be conducted to investigate the in vivo activity of rokitamycin, as an agent to be used in the combination therapies against H. pylori.