Molecular characterization of H. pylori: genetic diversity and vacA s1m1/cagA+ prevalence in Western Algeria.

Clinical outcomes of Helicobacter pylori infection range from chronic gastritis to peptic ulcer disease and gastric cancer. Yet data on strain diversity and clinical outcomes remain scarce in North Africa. This study aimed to characterise enzymatic and genetic variation among H. pylori isolates from symptomatic patients in western Algeria. From 428 patients, 72 H. pylori strains were isolated and purified; for genotypic analyses, 14 distinct strains were retained based on phenotypic diversity, clinical profiles, and DNA quality/quantity. Nitrate reductase activity, digestion of htrA and ureB, vacA (s1/m1) and cagA sequencing, and PCR-RFLP were performed. H. pylori was detected in 75% of chronic gastritis/gastric ulcer cases and 80% of duodenal ulcer cases. Nitrate reductase activity was high in duodenal-associated isolates (78.6% in bulbitis, 71.9% in bulbar ulcers), suggesting local adaptation. Seven distinct htrA/ureB profiles were identified. The vacA m1, vacA s1, and cagA genotypes were present in 80%, 10%, and 60% of isolates, respectively, with cagA restricted to m1-positive strains. Overall, these findings reveal a distinct enzymatic and genomic pattern of H. pylori in western Algeria, characterised by strain diversity, regional structural variants, and predominance of virulent genotypes. These results highlight the importance of local epidemiological and molecular surveillance and provide a basis for targeted management strategies. Further studies with larger cohorts and whole-genome sequencing are warranted to clarify the clinical impact of these regional H. pylori traits.