Beyond Helicobacter pylori: a critical review of Helicobacter heilmannii, an emerging zoonotic gastric pathogen

Background. Helicobacter heilmannii is a zoonotic gastric pathogen less common than Helicobacter pylori, yet associated with chronic gastritis and gastric mucosa-associated lymphoid tissue (MALT) lymphoma. Its epidemiology, pathogenic mechanisms and clinical impact remain poorly defined compared to those of H. pylori. Methodology. A narrative review of the literature was conducted to identify clinical, epidemiological, molecular and therapeutic data on H. heilmannii. Reviews, non-English publications, and inaccessible full texts were excluded. Results. The prevalence of H. heilmannii infection is low in Western countries, but higher in some Asian populations. The transmission is predominantly zoonotic, involving close contact with dogs, cats and pigs, being also associated with the consumption of animal-derived foods, such as milk products. Pathogenicity involves adhesion to gastric epithelial cells via specific adhesins, disruption of gastric mucosal integrity, oxidative stress and modulation of host immune responses. Studies revealed the absence of H. pylori specific virulence factors such as CagA and VacA, many outer membrane proteins and adhesins, but the presence of others, such as urease, γ-glutamyl transpeptidase, or proteases. Diagnosis is challenging, PCR and sequencing offering greater sensitivity and specificity compared to histology. Noninvasive diagnostic procedures and standardized protocols are lacking. The treatment typically mirrors H. pylori eradication regimens, but clarithromycin and metronidazole resistance present real concerns. Conclusions. H. heilmannii is an underrecognized gastric pathogen with distinct epidemiological and molecular characteristics compared to H. pylori. Improved species-specific diagnostic tools and large-scale clinical studies are needed to clarify its pathogenic role, optimize treatment strategies, and understand its contribution to gastric MALT lymphoma and other gastric pathologies.