Detection of A2142G and A2143G Substitutions among Clarithromycin-resistant Helicobacter pylori Strains Isolated from Egyptian Patients

Background: Clarithromycin is the most commonly recommended antibiotic in Helicobacter pylori ( H. pylori ) eradication regimens, but the prevalence of clarithromycin-resistant H . pylori is increasing. Clarithromycin-resistance is associated with mutations in the 23S rRNA gene. The study aimed to examine gene mutations (A2142G and A2143G) of H. pylori 23S rRNA responsible for resistance to clarithromycin. Materials and Methods: The study was carried out by collecting 53 H. pylori isolates. Isolation, identification and antimicrobial susceptibility to clarithromycin were done by standardized methods. Resistant strains were analysed for mutations in the 23S rRNA gene by polymerase chain reaction-based restriction fragment length polymorphism and sequencing. Results: H. pylori isolates were recovered from 91.4% of studied patients. About 64% were clarithromycin-resistant strains. The minimum inhibitory concentration (MIC) values of all clarithromycin-resistant isolates ranged from 1.5 to 8 µ g/ml. Primary clarithromycin-resistant isolates only showed a single type of point mutation (A2143G). In contrast, secondary isolates had dual diversity of 23S rRNA gene mutation types (A2142G and A2143G). Conclusion: Secondary clarithromycin-resistant isolates show a greater variety of 23S rRNA gene mutation types than primary isolates.