Gastric and Enterohepatic Non‐ Helicobacter pylori Helicobacters

A substantial number of reports published in the last year have contributed to a better understanding of both human and animal infection with non‐ Helicobacter pylori Helicobacter species (NHPH). Gastric infection of humans with Helicobacter suis and Helicobacter felis as well as unidentified NHPH has been described to cause a chronic gastritis and a variety of clinical symptoms, whereas enterohepatic NHPH, including Helicobacter cinaedi, Helicobacter bilis, and Helicobacter canis , have been reported to be associated with human diseases such as bacteremia, cellulitis, cutaneous diseases, and fever of unknown origin in immunocompromised hosts. In various animal species, including dogs and laboratory mice, high rates of infection with NHPH were described. For gastric NHPH, mainly H. suis and H. felis infection was studied, revealing that differences in the immune response evoked in the host do exist when compared to Helicobacter pylori . Pathogenic mechanisms of infection with Helicobacter pullorum, H. bilis, and Helicobacter hepaticus were investigated, as well as immune responses involved in H. bilis‐, Helicobacter typhlonius‐, and H. hepaticus ‐induced intestinal inflammation. Complete genome sequences of Helicobacter heilmannii strain ASB1 and a H. cinaedi strain isolated in a case of human bacteremia were published, as well as comparative genomics of a human‐derived Helicobacter bizzozeronii strain and proteome or secretome analyses for H. hepaticus and Helicobacter trogontum , respectively. Molecular analysis has revealed a function for type VI secretion systems of H. hepaticus and H. pullorum , the Helicobacter mustelae iron urease, and several other functional components of NHPH. In each section of this chapter, new findings on gastric NHPH will first be discussed, followed by those on enterohepatic Helicobacter species.