Genotype profiles of Helicobacter pylori from gastric biopsies and strains with antimicrobial-induced resistance

Abstract

Background and aims: The genotypic method could significantly shorten the time needed to obtain antibiotic susceptibility data for Helicobacter pylori. The aim of this study was to explore the profile of H. pylori from gastric biopsies and strains with antibiotic-induced resistance.

Methods: A total of 124 gastric biopsies were used to perform gene sequencing and to perform bacterial culture and susceptibility testing. Seven susceptible strains were selected to develop resistance to clarithromycin, levofloxacin, and metronidazole. Four susceptible strains were selected to transfer candidate mutations. The genotype profiles of these groups were analyzed by sequencing analysis. The antibiotic susceptibility of these strains was detected using the E-test method.

Results: Phenotypic resistance to clarithromycin, levofloxacin, and metronidazole was observed in 35.5%, 40.0%, and 79.8% strains, respectively. Point mutations in 23 S rRNA, gyrA, and rdxA genes were observed in 39.5%, 38.7%, and 86.3% of gastric biopsies, respectively. The A2143G mutation in the 23S rRNA occurs in most clarithromycin-resistant samples. The A2142C point mutation showed a higher efficacy than A2142G and A2143G for inducing clarithromycin resistance. The D91N and N87K mutations in gyrA occurs in most levofloxacin-resistant samples, and double point mutations showed a higher efficacy than single mutations for inducing levofloxacin resistance. Phenotypic resistance and mutations in rdxA lacked consistency.

Conclusion: Genotype-based gastric biopsy analysis was reliable for determining clarithromycin and levofloxacin resistance. A2143G in 23S rRNA and N87K/D91N in the gyrA gene occurred in most resistant strains. Mutations in the rdxA gene were not good indicators of metronidazole resistance.

Keywords: Helicobacter pylori; antibiotic; genotype; resistance.

Figure 1.

Profile of clarithromycin- and levofloxacin-related resistance genotypes in biopsies. (a) Prevalence of point mutations in 23S rRNA in total samples; (b) prevalence of point mutations in 23S rRNA in mutant samples; (c) consistency between the 23S rRNA gene sequence and E-test result; (d) prevalence of amino mutations in gyrA in total samples; (e) prevalence of amino mutations in gyrA in mutant samples; (f) consistency between the gyrA gene sequence and E-test results. Cla, clarithromycin; Lev, levofloxacin; MIC, minimum inhibitory concentration; R, resistant; S, susceptible; Seq-R, sequence result contain a point mutation (A2142G, A2143G, and/or A2142C point mutations for the 23S rRNA gene; point mutations resulting in the amino mutations N87K, N87I, N87S, D91N, D91Y, D91G, and/or D91K for the gyrA gene sequence); Seq-S, sequence result was the same as the reference sequence.