Determinants of resistance to levofloxacin and metronidazole in Russian <i>Helicobacter pylori</i> clinical isolates based on whole-genome sequencing data

Introduction. Helicobacter pylori infection, however, data on the mechanisms of metronidazole (MTZ) and levofloxacin (LVX) resistance in Russia remain scarce. and levofloxacin (LVX) in Russia. The aim of the study is to identify the determinants of resistance in clinical isolates of H. pylori to MTZ and LVX using whole-genome sequencing data. Materials and methods. A retrospective analysis of 43 H. pylori isolates obtained from adult patients (2014–2022) was conducted. Susceptibility to antibiotics was determined using the bacteriological disk diffusion method. Whole-genome sequencing of 43 H. pylori strains was performed using a DNBSEQ-G50 sequencer. Results. The evaluation of the phenotypic drug susceptibility test results showed that 11 isolates were susceptible to MTZ (MTZ-S), 31 were susceptible to LVX (LVX-S), while 32 isolates were resistant to MTZ (MTZ-R), and 12 were resistant to LVX (LVX-R). To identify the association between phenotypic and genotypic resistance, an analysis of nucleotide substitutions in the gyrA, gyrB, rdxA, frxA, fdxB and fur genes was conducted. Of all the mutations identified in the gyrA and gyrB genes, only D91/GNY in the gyrA gene was associated with phenotypic resistance to LVX and was found in 4/12 (33.3%) of the isolates (p 0.05). The combined mutation D91G/N/Y+N87K in the gyrA gene was detected in 6/12 (50.0%) of LVX-R isolates (p 0.001). Point mutations in the rdxA gene were detected in 21.9% (7/32) of MTZ-R isolates, leading to a frameshift or premature termination of protein synthesis. None of the mutations in the frxA, fur and fdxB genes were associated with H. pylori resistance to MTZ. Conclusion. Based on the results of whole-genome sequencing of Russian clinical isolates of H. pylori, the detection of the combined mutation D91G/N/Y+N87K in the gyrA gene can serve as a predictor of the phenotypic resistance of H. pylori to levofloxacin.