The first two human infections with Helicobacter zhangjianzhongii, a new Helicobacter closely related to Helicobacter canis.

Purpose: In 2023, Helicobacter zhangjianzhongii was proposed as a new species in the Helicobacter genus. We here describe two human cases of H. zhangjianzhongii bacteremia.

Methods: Four clinical strains from the Helicobacter genus isolated from blood culture between 2017 and 2023 were studied. They were initially identified as H. canis by MALDI-TOF and 16S rDNA sequencing. The strains were biochemically characterized and tested at different temperatures and atmospheres. Two databases were used to characterize the isolates: the Bruker® MBT compass Version 4.1.1 database and a in-house spectrum-enriched database. After bacterial DNA extraction the genomes were sequenced on NovaSeq 6000 (Illumina) and analyzed using an in-house pipeline.

Results: Case 1 involved a 58-year-old woman who was hospitalized in a thoracic oncology unit because her general condition deteriorated in a setting of small-cell carcinoma. She presented with abdominal pain associated with significant hepatomegaly. Case 2 involved a 78-year-old woman on rituximab who was hospitalized to treat chest pain, anemia, and inflammatory syndrome. Both strains exhibited very similar microbiological and genomic characteristics, thus growth in a microaerobic atmosphere at 37°C and 42°C, oxidase-positivity, and urease- and catalase-negativity. Both were formally identified by whole-genome sequencing as H. zhangjianzhongii (ANI > 99% and DDH > 94%).

Conclusion: This proposed species is associated with bacteremia in humans. It is thus likely to be a novel human pathogen. Dogs may have been the source of infection.