Nitazoxanide and Doxycycline Sensitivity Among Metronidazole Resistant Helicobacter pylori Isolates from Patients with Gastritis

Antibiotic therapy should be done based on resistance characteristics of Helicobacter pylori strains to commonly prescribed antibiotics in areas with higher resistance rates.
This study examined antibacterial activity of nitazoxanide and doxycycline against clinical H. pylori isolates showing different metronidazole resistance levels.
A total of 122 patients, who underwent endoscopy were enrolled in this study from 3 hospitals of Tehran, during November 2014 to July 2015. Helicobacter pylori isolates were obtained from gastric biopsies of the patients after culture in specific culture medium and characterization by both biochemical and molecular methods. Antimicrobial susceptibility to metronidazole was detected using the agar dilution method and minimum inhibitory concentrations of nitazoxanide and doxycycline were determined for metronidazole resistant strains.
From a total of 122 gastric biopsy specimens, 55 H. pylori strains were recovered (45%). Thirty-three of these strains (60.0%) were resistance to metronidazole. MIC50 and MIC90 values for metronidazole were 32 and 64 µg/mL, respectively. MIC50 and MIC90 values for doxycycline and nitazoxanide were measured as 4 and ≥8 µg/mL, and 8 and ≥32 µg/mL, respectively.
Dominance of high level metronidazole resistance H. pylori strains among the studied patients questioned its usefulness for first-line therapy in Iran. Nitazoxanide and doxycycline showed superior activity against H. pylori strains in comparison to metronidazole, which should be considered for alternative therapies.