The antibacterial activity of TAK-083 was tested against 54 clinical isolates of Helicobacter pylori and was compared with those of amoxicillin, clarithromycin, and metronidazole. The growth-inhibitory activity of TAK-083 was more potent than that of amoxicillin, clarithromycin, or metronidazole (the MICs at which 90% of the strains are inhibited were 0.031, 0.125, 64, and 8 microg/ml, respectively). The antibacterial activity of TAK-083 was highly selective against H. pylori; there was a >30-fold difference between the concentration of TAK-083 required to inhibit the growth of H. pylori and that required to inhibit the growth of common aerobic and anaerobic bacteria. Exposure of H. pylori strains to TAK-083 at the MIC or at a greater concentration resulted in an extensive loss of viability. When four H. pylori strains were successively subcultured in the medium containing subinhibitory concentrations of TAK-083, no significant change in the MICs of this compound was observed. TAK-083 strongly inhibited the formation of tryptophanyl-tRNA in H. pylori while exhibiting little effect on the same system in eukaryotes. TAK-083 was efficacious in the treatment of gastric infection caused by H. pylori in Mongolian gerbils. The results presented here indicate that TAK-083 is a promising candidate for the treatment of H. pylori infection.