Nitazoxanide, a nitrothiazolide antiparasitic drug, is an anti-Helicobacter pylori agent with anti-vacuolating toxin activity

Nitazoxanide (NTZ), a synthesized drug of the nitrothiazolide class, was in itially developed as an antiparasitic compound. This compound has recently been shown to have antibacterial activities against some bacterial pathogen s. In the present study, NTZ and its main metabolite tizoxanide (TIZ) were found to have strong minimum inhibitory concentrations (MICs) against both metronidazole (MTZ)-resistant strains and sensitive clinical isolates of He licobacter pylori. The MIC90 of both NTZ and TIZ against 37 clinical isolat es was 8 mu g/ml. Vacuolating toxin activity of H. pylori assayed by HeLa c ell vacuole formation was inhibited by NTZ at a sub-MIG. In contrast, ureas e production by H. pylori was not specifically affected by the sub-MIG of N TZ. An acidic pH (pH 5.0) medium reduced the antimicrobial activity of the drug in terms of growth inhibition due to the low growth rate of the bacter ia, but killing activity of NTZ against the bacteria was still observed. Th us, it was apparent that both NTZ and TIZ are highly effective against H. p ylori, even when the bacteria are resistant to MTZ.