Saeed Bayati - Department of Microbiology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran
Masoud Alebouyeh - Foodborne and Waterborne Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, ShahidBeheshti University of Medical Sciences, Tehran, Iran
Nasser Ebrahimi Daryani - Department of Gastroenterology and Hepatology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
Mohammad Reza Zali - Gastroenterology and Liver Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Science, Tehran, Iran

Background: Eradication failure of Helicobacter pylori infection could play a causal role in progression of gastric disorders. Methods: Accordingly, overall changes of resistance and minimal inhibitory concentration (MIC) of H. pylori strains to metronidazole, clarithromycin, and ciprofloxacin were studied in adult patients at two phases during 1 year period. Furthermore, association of therapeutic regimens with the refractory infection, changes of MIC values, and progression of histopathological changes were analyzed. Results: Among the infected patients at early phase of the study (32.3%), persistent infection with H. pylori was confirmed in 14 patients (56%) at the second phase. The results showed progression of the disease based on the histopathotological or endoscopic findings. A difference between primary and secondary resistance rates to clarithromycin (49% vs64.3%), metronidazole (76.36% vs100%), and ciprofloxacin (45% vs57.1%) was detected. Two fold increases in MIC50 values of clarithromycin and ciprofloxacin was detected at the second phase. Patients with intestinal metaplasia showed significantly higher resistance rates to all antibiotics. While ciprofloxacin-based regimens were more successful, failure of metronidazole based regimens was detected in 77% of the patients. Conclusion: Collectively, these results showed adverse effect of inappropriate medication on refractoryH. Pylori infection with a rise in resistance levels to antibiotics, resulting in progression of pathological disorders.

Helicobacter pylori, Eradication failure, Antimicrobial resistance, Therapeutic regimens, Pathological changes