Helicobacter pylori antimicrobial resistance and gene variants in Shandong Province

The emergence of antibiotic resistance in Helicobacter pylori led to a sharp decline in eradication rates, but there are limited data regarding the prevalence and genetic mechanisms of antibiotic resistance in Shandong. This study aims to assess the prevalence and molecular mechanisms of H. pylori antibiotic resistance to commonly used antibiotics in Shandong populations. Antimicrobial susceptibility testing was performed for clarithromycin, levofloxacin, metronidazole, tetracycline, rifampicin, amoxicillin, azithromycin, and moxifloxacin using E-test method. PCR amplified resistance-associated genes for all the strains, and 32 were whole-genome sequenced. 62 H. pylori strains were obtained and the infection rate was 30.1% (62/206). No resistance to amoxicillin was observed. Two and four strains were resistant to tetracycline and rifampicin, respectively, and no resistance-associated mutations were found in the 16S rRNA and rpoB genes. The resistance rates of azithromycin, clarithromycin, levofloxacin, and moxifloxacin were 56.45% (35/62), 33.87% (21/62), 48.39% (30/62), and 56.45% (35/62), respectively. The percentages of dual, triple, and quadruple resistance were 32.26% (20/62), 24.19% (15/62), and 1.61% (1/62), respectively, and only one isolate was resistant to quadruple antibiotics. Phenotypic resistance associated with the A2143G mutations in 23S rRNA for azithromycin and clarithromycin (kappa coefficient, 0.808 and 0.671, respectively), and gyrA mutations (N87K/N87I/D91G/D91Y/D91N) for levofloxacin and moxifloxacin (kappa coefficient, 0.526 and 0.442, respectively). Metronidazole resistance was observed in 43.55% (27/62) isolates and most of the metronidazole-resistant strains had truncated rdxA and frxA. The detection of a truncated rdxA gene correlated with phenotypic resistance results (kappa coefficient, 0.728). There was no association between whole-genome phylogeny and antibiotic resistance profiles. Our results revealed the high resistance rates and multiple resistance of H. pylori to commonly used antibiotics. Continued surveillance of H. pylori antibiotic resistance is crucial in Shandong to establish effective eradication therapy for this population.