Assessment of Metronidazole and Clarithromycin Resistance Among Helicobacter pylori Isolates of Ahvaz (Southwest of Iran) During 2015 - 2016 by Phenotypic and Molecular Methods

Helicobacter pylori, a Gram-negative bacteria, is the most important cause of gastric ulcer, gastric malignancies, and chronic gastritis. Clarithromycin is recognized as the most important antibiotic for the treatment. Clarithromycin resistance is related to point mutations in the 23srRNA, and the most important mutation is A2143G, A2142G. The most common cause of resistance to metronidazole is rdxA gene mutational inactivation. This study aimed to evaluate clarithromycin and metronidazole resistance in H. pylori by phenotypic and genotypic methods. In total, 338 gastric biopsy samples were collected. The samples were cultivated on Colombia agar, consisting of various antibiotics and were incubated at 37°C under microaerophilic conditions. The biochemical tests and PCR assay were applied to identify the strains as H. pylori. The E-test was applied in the antibiogram test based on CLSI standard. The PCR-RFLP assay was performed to identify point mutations and followed by sequencing. The PCR method was done to identify deletion of a 200-bp fragment from the rdxA gene. In total, 131 (38.7%) H. pylori strains were isolated that among them, 70 (53.4%) and 83 (63.4%) showed resistance to clarithromycin and metronidazole, respectively. Prevalence of A2143G, A2142G, A2142C mutations were 71.4%, 7.1% and 4.3%, respectively. Seven (8.4%) strains, included 200-bp deletion. The high prevalence of resistance to clarithromycin and metronidazole in H. pylori is a major concern revealed by this study which should be taken into account by physicians in selecting drug regimens. The results confirmed the necessity of phenotypic and genotypic methods of antibiotic susceptibility.