Genetic basis for metronidazole and clarithromycin resistance in Helicobacter pylori strains isolated from patients with gastroduodenal disorders

Genetic basis for metronidazole and clarithromycin resistance in Helicobacter pylori strains isolated from patients with gastroduodenal disorders Seyed Jalal Hashemi,1–3 Ahmad Farajzadeh Sheikh,1,4 Hamed Goodarzi,1,4,5 Mohammad Jaafar Yadyad,1 Seyed Saeid Seyedian,6 Sajad Aslani,7 Mohammad-Ali Assarzadegan8 1Infectious and Tropical Diseases Research Center, Health Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran; 2Research Institute for Infectious Diseases of the Digestive System, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran; 3Division of Gastroenterology and Hepatology, Ahvaz Jundishapur University of Medical Sciences, Ahwaz, Iran; 4Department of Microbiology, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran; 5Molecular Biology Research Center, Baqiyatallah University of Medical Science, Tehran, Iran; 6Alimentary Tract Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran; 7Student Research Committee, Kerman University of Medical Sciences, Kerman, Iran; 8Immunology Department, School of Medicine, Iran University of Medical Sciences, Tehran, Iran Background: The aim of this study was to evaluate the antimicrobial resistance and genetic basis for metronidazole (Mtz) and clarithromycin (Cla) resistance in strains of Helicobacter pylori, isolated from patients with gastroduodenal disorders. Patients and methods: A total of 157 H. pylori isolates (from 22 gastric cancer, 38 peptic ulcer disease, and 97 non-ulcer dyspepsia patients) were analyzed for drug susceptibility to Mtz and Cla, by gradient diffusion test (E-test, MAST). The PCR and sequence analysis of the rdxA and frxA for Mtz-resistant strains and the 23S rRNA for Cla-resistant strains were used to determine the genetic basis of drug resistance in H. pylori strains. Increased expression of TolC homologous genes (hefA) that upregulates efflux pump activity was determined in multidrug-resistant (MDR) strain of H. pylori by real-time PCR technique. Results: Among 157 H. pylori isolates, 32 (20.4%) strains were resistant to at least one of the antimicrobial agents. The highest resistance rate was attributed to Mtz (n